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Can anyone coomment on this observation from an old Aussie sniper from Korean War:
"As the rifle bolt on the .303 is locked at the rear, there would be a crossover of shots at between 900 and 1200 yds. This was an odd characteristic of the Lee Enfield. It meant that the rounds would impact to the left or right of the aiming point. … Rifle was zeroed at 300 yds" He was firing the No.1 HT.
Was this a well known aspect of the SMLE?
Cheers
Glenn
Its hard to understand what he is describing. Does he mean that there is a lateral spread in the group, between 900 & 1200 yards?
If so, thats not a known general characteristic of No1 rifles. Maybe the HT mount itself is flexing, and the error simply amplified by distance? Normal No1s have both sights on the barrel and grouping is not particularly affected by what goes on behind the chamber.
No1s are highly individualistic; they made over 4 million of them , but they're all different.....
Shooting a SMLE, with or without the primitive optics of the old Patt 18 scope, at 1200 yards would be an exercise in optimism. I would think that targets at that range would be at least "Jeep" sized.
900 is certainly do-able, as it was and still is, one of the more "challenging" distances for "full-bore" shooting.
I gather that what the writer means by "crossover", is lateral dispersion.
Do any (still-youthfull) Bren or Vicker drivers have any similar experiences?
As I have mentioned before, the actual path of a bullet is rarely a perfectly smooth parabola. The miniscule variations in jacket and core construction mean that bullets are unlikely to spin around their actual dimensional centre-line. Then there is the equally miniscule variations caused to the airflow by the fact that the bullet is, in fact, spinning at several hundred thousand revs per minute. Take into account variations in air density, humidity, ammo temperature, barrel temperature and it starts to get interesting.
Finally, consider that the rotational velocity does NOT decrease very much as the bullet goes downrange. LINEAR velocity does, however.
SO, what may be happening is that the bullet is spun at least fast enough to achieve stability at any practical temperature and air density on the face of the planet. The trick is that as the range increases, "linear" velocity decreases. The outrageous initial rotational velocity means that the (over) stabilised bullet tries to stay aligned with the line of departure at the muzzle. What this means is that, at SEVERAL intervals along the "parabolic" trajectory, the pointy end will no longer be exactly aligned at a tangent to the curved trajectory.
Eventually, aerodynamics has a brief struggle with rotational inertia and the the bullet, already "precessing" (describing a tiny spiral motion AROUND the actual "trajectory) jumps randomly until the aerodynamics haul it back into line.
The new "stable state" is very likely to NOT be exactly on the original trajectory: it could be to either side of it. The more "excessive" the rotational stability, the longer it will take to re-stabilise.
If your barrel was elevated 15 degrees to land bullets at some range, then the bullet will try to keep pointing at 15 degrees, until such time as the aerodynamics overcome it. If this happens in tiny increments at short intervals, the relative grouping deviations will be small. If your bullet is OVER stabilised, the corrections will be fewer and MUCH bigger as it travels down-range.
Mk7 bullets are only spun at their speed becaise of their length. The bullet is within a whisker of the same length as the heavier, round-nosed Mk6 that preceeded it. The higher muzzle velocity of the Mk7 means, of course, a correspondingly higher rotational velocity, and thus a completely different set of down-range dynamics. I suspect that this maintenance of length was to not require that every .303 weapon be re-built to reliably feed a shorter projectile.
Once the bullet has left the bore, then it's on its way, under its own steam and whatever happened in the rifle has ended. Thereafter will have no effect on it (I may have said that slightly incorrectly..............). If it does go left or right or up or down, then it does so due to other influences.
You know my experiences with the old and bold and their versions of events relating to small arms...........
never heard this one in regards smle's as a rule, except when hunting with cheap rifles and home made scope installation on LE s.
My simple minded 2 cents, inflated ones with little value, if this was my sporterised enfield hunting rifle with a cheap scope on it, and the shots showed a cross over, the simple thing I'd look at is that the scope is not parallel to the bore in the yaw axis, and intersects the line of sight/shot at a particular range. If the scope were zeroed for that range it would shoot eg left at shorter ranges and shoot right if one raised it a couple of hundred yards. I'm not sure if Hts all had scopes but that would be my first approach.
I think the comment that it was zeroed for 300 yards is a mental diversion, this is about the scope being parallel to the bore, or not, not the range drum zero.
Quote:
Originally Posted by RJW NZ
Add my 2 cents to that. It is a well-established (but often overlooked) performance inhibitor on the Mosin-Nagant sniper rifles, where people have often retrofitted PU scopes without realizing that the scope axis needs to be accurately above the bore axis in the vertical plane.
The phenomenon of lateral deviation of bullets has been known for quite a while.
That's why the old Lee Enfields ("Long Toms") had "issues" with sighting in the early days. Issuing a new "mark" of ammo every year or so wouldn't have helped at all.
Note that from early days, SMLEs had their front sight bases offset from dead-centre by a noticeable amount. (I am not in "The Crypt" as I type this and the exact offset escapes me. The "ears" on the nosecap are similarly offset so that the sight picture is not too "wonky".
The bullets had lateral drift in still air and thus compensation had to be built in. This was achieved by offsetting the "nominal" centre line of the front sight assembly.
Quote:
Originally Posted by gwahlert
I see no connection between the rear locking and any recurving of the sideways drift in the air - but I await enlightenment. As Peter has delicately hinted, once the bullet is in the air it has no "memory" of being fired from an Enfield or anything else. What it has are solely the ballistic characteristics of its form, plus the velocity, spin, yaw etc imparted on firing. Which may also be influenced by the deformation of the system on firing. But once the bullet has left the barrel, it is hard to imagine that a bullet thinks "OMG, I was fired from an Enfield and now I'm past 900 yards, time to start curving back!":madsmile:
The phenomenon of a bullet fired from a rifled barrel drifting one way or the other, depending on the direction of twist, has been know since blackpowder days. This results from the attitude of the bullet in flight, not the locking lugs in the system that fired it, and hence will increase in a non-linear fashion with distance, depending also on the tractabiity i.e. the way the attitude of the bullet alters during the curve of the trajectory.
Take a look at the Buffington sights on a Trapdoor, and you can see that the backsight leaf is angled very slightly to compensate for this effect. Which is the same effect as used by spin bowlers to make the ball curve in the air. Surely every Aussie knows that, unless they live a highly secluded existence and have never heard of Shane Warne!:madsmile:
My only thought here is to wonder if a lateral crossover at long distance could be caused by wind drift with winds down range being significantly different than anticipated, and the rear locking of the bolt theory was just barrack room speculation becoming gossip becoming gospel. Thoughts?
One of the many good things about a forum is that you can air all sorts of ideas and ask all sorts of questions and nobody really gives two hoots. Even if to others they might seem silly, daft or just plain stupid, you'll always get answers. In classrooms, I always say that there's no daft, silly or stupid questions - just questions that deserve answers
But it is better to ask and discuss these things here (or in the class) than to go full steam ahead and publish them. That way, the readers KNOW that you're daft, silly or just plain stupid
Agree 100%, always a pleasure to see brains cells flexing their muscles.Quote:
Originally Posted by Peter Laidler
I've been sitting here trying to form an answer built around distance and zeroing and ......
Either irons or optics, it's easier to zero at closer distances. 'Zeroed' at 25 yards/meters you shoot a ragged hole you can barely poke your finger through. Zeroed at 50 it opens up a bit. A bit more at 100. My mind sees that the front sight or reticle covers increasingly larger percentage of the helmeted head target.
So, now you're zeroed at 300. If it's like the #4 zeroed means what, get 'em all in a 3x5 target? Now you're asked to hit Herr Offizier at 900 yds/mtrs. Even on a calm day the thickness of the reticle will cover the guy's whole shoulder span, no? Bound to be some lateral offset, I would think. Maybe that's all it is. It's easier to zero and then hit something at closer ranges.
Remember Peter said:
Oh, and, I have a History degree not physics!:cool:Quote:
Originally Posted by Peter Laidler
What about about spin drift.
I have only read a little about long range shooting and up here 500 yds is long range:madsmile: so I don't know the extent of its effects but the bullets rotation causes horizontal drift that is noticeable enough to be figured into a snipers long range shot calculations.
As we all know the fall of shot of a smle is affected by the fit of the nose cap and also the "v block" in the barrel opening in the aforesaid nose cap.The nose cap will centralize the barrel as it whips up as the bullet leaves the barrel and any grot at that point will affect the direction of the bullet.Just a thought ! Cheers Ross
I don't think rotational drive plays any part in the direction of the bullet. I have watched thousands upon thousands of bullets from Vickers guns hitting the target area on an upswept bank on the field firing ranges at 2 miles away. And watching the fall and hits through binos, they all seem to go where the gun is aimed
The only known example of a SMLE Sniper having a point of impact that would coincide at 300 yardsand then open out beyond that is with the Great War Sniping Weapons with the scope offset to the right. The point of zero of the WWI sniper weapons was set at 300 yards, this naturally meant that the point of impact at less than 200 yards was to the left of point of aim, coinciding at 300 yards and beyond that it would move progressively to the right of point of aim. The British sniper would in time learn to use the method of aiming that had cost him so dearly in the America's, namely kentucky windage. The same Kentucky windage/elevation that once learned has served our specialists well from WWI through WWII and Korea to the present day in Afghanistan.
Cheers,
Simon,
P.S. Sorry if the above is a tad incomprehensible, we've actually had a decent days weather in the North West UK today so I may have had the odd one or three beers at the BBQ before posting the above
Spindrift does effect bullet travel but further reading puts it at about .5 moa at 1000 yds with a .308 Winchester firing a 168 grain Sierra MatchKing bullet. so for all practical purposes it looks like you are correct. No effect.
What earthly planet were they on to teach this ludicrous method of zeroing an offset telescope? Is that a recorded fact Simon? Zero an offset foresight (that's all a grat is of course.....) at 300 yards! You'd only ever be able to at BEST, guestimate anything beyond that with the accumulative effect of the error and........ and........................
It's a good job that they didn't utilise that ludicrous notion with the Bren gun - and don't forget, the grat of an optical sight is always a foresight. Just take the Bren Gun........ The rear and foresights are exactly 1" to the left of the mechanical/true axis of the bore. It is sighted at the aiming point and the MPI of the shots must fall 1" to the right of the POA. And it'll hit 1" to the right all the way out to wherever, the bullets fall 1" to the right of where you're aiming. Not that it makes any difference with a Bren of course.
But what it does mean is that from 25 to 1000 yards, you'll be hitting the man 1" to the right of where you actually aimed. But at least if they used the same forumla, even if it's 1.5" offset with the offset telescope you'd still be hitting the man at 600 or even 900 yards albeit 1.5" to the right. Which in my humble opinion is better than guessing a) the range and b) how much to aim off
Or am I missing something?
Peter,Quote:
Originally Posted by Peter Laidler
I couldn't agree more!!!! Lets face it though the whole concept of offsetting the scope is ludicrous and resulted in British loophole plates having a condiderably "bigger ole" than the German ones. I do recall seeing the zeroing criteria in print in a manual / title of that era, please don't ask which one though as it could take weeks of trawling to find it again.
Out of curiosity perhaps one of our cousins from over the pond can comment on the zeroing criteria of the M1C and M1D as the en-bloc loading of these weapons required the scope to be slightly offset.
Cheers,
Simon.
I would like to see this if and when you can find it. Reading the 1920 Small Arms reports of a captured German 'swing-turret' mounts made mention of the fact that offset mounting, as close as possibly level with the rifle bore was the best option over a higher mount for several reasons. The principal one being that the eye relief of the sniper is not constant* and for every extra bit of optical height radically alters the relationshipo between......blah blah blah and on it goes.
* I don't understand this either because eye relief is eye relief is eye relief UNLESS they mean comfortable eye position - as with the later cheek rest
As a matter of interest, the zeroing criteria of the AK47 and Dragunov offset telescopes and the Bren on the anti-tank gun and the night vision on all and sundry is all to the left - as is/was the sub calibre round for the Carl Gustav 84mm anti-tank. Mind you, 3" to the left of the aiming point on a tank is a bit academic really. Unless you are one of the tankies and have been hit!
Is that actually noted in a drill book somewhere, or is that from accumulated sniper lore?Quote:
Originally Posted by Simon
I ask, because my PPCo (admittedly of completely unverifiable provenance) has the scope parallel to the bore in the horizontal axis (or is that the vertical axis?!); hence the POI remains offset to the left by a fixed amount at all ranges. Given that the offset is only about 1 1/2", it would seem pointless trying to have a "converged zero" at a specific range plus correction factors for every other range - far easier simply to aim 1 1/2" to the right, whatever the range.
Getting back to the OP's anecdote, the answers must surely be; (1) no, No1s do not typically exhibit lateral spread; (2) any lateral spread reported by the sniper is most likely down to a fault in scope/ mount/ shooter on that particular rifle....
The rear locking of the Lee-Enfield action is well known to "compensate" at longer ranges but up and down NOT laterally. Maybe the old boy was heard incorrectly or had got confused.
I'm inclined to agree with Thunderbox. Simon, is there any chance (at your convenience of course) you might dig out this literature re all offset SMLE scoped snipers, as I'd have thought it more logical & consistent to mount the scope parallel to the bore so the amount the sniper had to aim off was constant? I have been getting repro's of many of these mounts made now for over ten years, & whilst I have no control over who has subsequently fitted them to rifles I know that several eminent gunsmiths known to these pages have done so. I would be interested to know if they were machined up to sit parallel or convergent.
Oh, & the scopes weren't offset to the right - it was to the left....I presume you'd had one over the eight when you typed that!
ATB
The old chestnut about No1's 'compensating' for, well, whatever it was, nobody really seems to have identified it was regularly aired during class discussions and especially later at academic level. As pointed out earlier and repeated by Patrick, once the bullet has left the bore, it has no memoiry so quite how it comensates is anyones guess.
Like T/box,I eagerly await any printed matter about offset telescopes or even open sights being zeroed without the offset being taken into account.
I was always intrigued by full-bore shooters who used a SMLE or No4 for some distances and a P-14 for others: similar length barrels, generally the SAME sighting units.
I heard various stories about different rifles shooting "better groups" at oddly divergent ranges.
As Peter noted, once the bullet has left the muzzle, the barrel has NO more effect on it. (Irregular muzzle-blast dispersion aside). So, given that EVERYBODY was using the same, bog-standard Mk7 ammo, what, if anything, could be happening? (Apart from 20th Century Voodoo)
The waves that are generated in a barrel from the moment the trigger is pulled to the point of departure are immensely complex. The wave patterns are multi-mode: vertical, horizontal, axial and torsional; all at the same time. It is variations in these, from shot to shot, that cause the most grief after the ultimate insult of a dodgy crown. This is why proper bedding is supposed to produce CONSISTENCY in the wave patterns from shot to shot as it CANNOT eliminate them. If the muzzle is pointing up a squillionth of a degree EVERY time a bullet departs, that is consistency and you just go with it. What you end up with is a set of behaviours that suit your ammo. That is why, every time you fiddle with your ammo, either by changing brands of factory fodder or the balance of components in "home-brew" that you end up back at the range to re-zero.
Mk3* SMLEs and No4s were build around Mk7 ammo, end of story. (Lets just gloss over the odd allowance for Mk 6 ammo in the throating of SMLEs for a minute). If you "free-float" a No4, it MIGHT shoot with a handload that you come up with eventually, but it is almost impossible that it will both group the same AND to the same point of impact with said Mk7 ball. If you wind a Lithgow heavy barrel into your SMLE action, it will NOT perform the same as the original barrel. After you have cheerfully removed a lot of wood and deleted sundry bedding gizmos that were used on the standard barrel, one could hardly expect it to. It may be better; it may be not. Most of any improvement will possibly come from the simple fact that said heavy barrel is (hopefully) NEW and has not yet had its throat burned out by cordite or its crown blasted away. As for the interesting practice of opening out the muzzle hole in the nosecap with a hand-held rat-tail file and bashing in a bit of rubber hose as a "bearing"...........
Back in the days before Oz lost its sense of humour about such things, I worked on a lot of M-14 / M1A rifles. One regular job was to give them the AMTU match rifle treatment (minus the NM barrel, of course). This worked well in MOST cases. However, the improved groups were generally NOT terribly close to the original MPI. Re-zero and carry on! One chap insisted on having his “free floated”, i.e., there was no “pull-down’ of the barrel by the cap behind the gas cylinder. This rifle shot F4 and M80 ball all over the place; but with hot-loaded 125gn Speers, it was a screamer.
[QUOTEOh, & the scopes weren't offset to the right - it was to the left....I presume you'd had one over the eight when you typed that![/QUOTE]
Doh:banghead: "Stupid Boy Pike"
Roger,
I'm not saying that mounting system was machined to collimate at 300 yards, far from it. There is only one way the mounting systems can be installed and that is by carefully machining / installing them to be parallel to the bore of the weapon.
What I am saying is that I have read somewhere, unless I'm losing my bloody marbles:madsmile:, that the pointer of the grat was zeroed to coincide with the point of aim at 300 yards. I'm not disputing the point that if the scope is offset 1 1/5" to the left of the bore then all that Tommy Atkins has to do is simply aim off by the same amount at any given distance. Lets step back a minute and way a few things up, the weapon / scope combo's where set up by PP Co, Whitehead Bros, Wm Evans, Holland & Holland, Purdey, Watts, Bartle, Atkin etc etc. So each manufacturers mounting system would be offset to a different degree and machining and installation tolerances would also result in a difference in offset, can you see where I'm going with this?
Tommy Atkins is issued with his, for arguments sake PP Co / PP Co SMLE, who tells him what the offset of his scope is? Lets assume, again for arguments sake, that he's at the Sniping School and the Sergeant Armourer informs him of his offset and he proceeds to zero the weapon on a KD range. At what range does he zero the weapon? Yes it does matter because because if he sets up at 100 yards and is only 1/8" out the weapon would be 1/2" out at 200 and so on and so on. And that would be setting up the weapon under nice controlled conditions where no bugger is likely to be shooting back at you.
The next step is that Tommy is off into the front line to "have a bash at Fritz". He spots said "Fritz" about 250 yards away and takes aim, as he's been taught, 1 1/2" to the right of said German Bonce and lo and behold misses because the small error in zeroing is exagerated as the distance to target increases. Lets be honest here too, you've got a 2 1/4x scope with a grat that as good as obscures the target and we're expecting Tommy to somehow manage to aim 1 1/2" inches off? God forbid he ever has to adjust deflection in or near the front line when the aiming point might be a distant tin can or some or piece of Battlefield debris.
So lets examine the point of impact zero at 300 yards theory. Under the controlled conditions of the Sniping School he sets his POI and off he pops to the front line. Now we pick up the same scenario as above except we know that the weapon is on at 300, there's no need for him to even remotely consider aiming off. He places the pointer on the bridge of the nose of his intended victim and pulls the trigger, result? A hit. Albeit 1/2" to the right of his point of aim. Should the need arise to adjust the telescope he doesn't have to make sure his hits are consistently 1 1/2" to the left of his point of aim he merely picks his tin can and tries to hit the bloody thing, no mean feat in itself when the target is likely obscured by the Grat pointer anyway.
I can see the logic in both theories but be honest with yourself, ignoring the fact that the offset scope idea is ridiculous anyway, which zero set up would find the simplest to maintain?
Cheers,
Simon.
P.S. Its worth keeping in mind that the vast majority of the trench lines were anything from 50 to 350 yards apart.
P.P.S. Yes it sounds ludicrous to zero for offset scopes etc but the thinking of the time wasn't exactly enlightened was it? Mass Human wave assaults, using shrapnel shells to cut barbed wire, one last big push and we'll send in the cavalry, offsetting the scope in the first place so you can clip load the weapon, and lets not forget that as late as 1915 a considerable number of the officer class still considered Sniping to unsporting. The list goes on and on
Simon,
Thanks for clarifying. I get your drift, & in fact your point is probably another variation of what was done in practice. However, I am going by what it says in pam SS 195 Scouting & Patrolling (December 1917), page 50, viz:
'Offset - With the telescopic sight fitted to the left side of the rifle, it is necessary to allow for ''offset'' when zeroing deflection. The sight should be adjusted so that at 100yds range the shots strike one & a half inches to the right of the point of aim. A rifle so zeroed may be taken as shooting straight for all sniping ranges. Only when shooting at a small mark, such as a loophole at 100yds should this one & a half inches be allowed in aiming.'
After reading the various postings I thought I might have seen something on the matter in SS195 at some point in the dim & distant past, so I dug it out.
I may be interpreting it wrongly but it suggests to me that the pointer on the scope is zeroed to be pretty much parallel to the line of the bore - I know there were various scope & mount manufacturers, but one & a half inches is probably a reasonable approximation to the average offset of most scope/rifle combo's; & it is the also the amount of offset at 100yds. Having said that, I would agree there is clearly a degree of compromise implicit in these instructions, which have to be applied to a variety of scopes & scope mounting systems.
My brain's starting to hurt now....
ATB
Correct me if I'm wrong. but a scope offset by 1 1/2 inches to teh left, and zero'ed at 300 yards, would hit 1 1/2 inches to teh left at 600 yards assuming the bullet didn't swerve due to rotation a la shane warne. Given the date I woudl think this would be an acceptable compromise for the sniper, though probably not the CORRECT way of doing things.
Not an old chestnut at all Peter. It may not have been discussed in class but it was regularly discussed in Guns Review in the days before purpose-built 7.62mm rifles like the Swing.Quote:
Originally Posted by Peter Laidler
The result, based on the experience of the contributors was: was P14s for Century and No.4s for Stickledown.
As to the the bullet having no memory, are you sure? That memory being based on what the barrel/action was doing during it journey up it and just as it left it. For example the rifling in a barrel causes a bullet to spin during the whole course of its subsequent journey.
Er........... No Simon, the amount of offset (within the bounds of reason of course) between each manufacturer is pretty well academic to the sniper, as is the distance between trenches and anything else. The only thing he's concerned with is distance. There is no earthly logic in the zeroing at 300 yards theory........ it is doomed to failure at any other distance, near or far. Better to zero in exactly as taught, by the book as detailed by DRP in thread 27 and be sure that you'd hit the man at any (?) distance, albeit 1.5" to the right.
After reading 'the book.....' in thread 27, I cannot imagine for the life of me, some budding sniper telling the sniping school staff that he's had a brainwave and he's got a theory that it'd be better to zero his rifle at... and.......... Nope, it wouldn't work. Like I said. Better to hit 1.5" off or slap bang on if you aim off a tad than miss totally for want of remembering some mathematical formula. To be honest, some of them couldn't even remember the range scale clicks up the scale, knowing that it would be one of the end of course exam questions!
Quote:
Originally Posted by Rumpelhardt
That is the effect I already mentioned. The attitude of the bullet is the slight upwards tilt of the nose compared with the trajectory at that instant. As gravity starts to win and the bullet drops, so the attitude diverts more and more from the trajectory. The ability of the projectile to alter its attitude to follow the trajectory is termed tractability. But the bullet will always have some attitude angle, because it is always dropping under the influence of gravity. This means that the lower surface has a higher air pressure on it than the top surface. Putting it totally non-scientifically, the bullets "bites " into the air more on the lower surface, and thus tends to crawl in the direction of the spin.
A cricket ball has a very rough surface, and the seam makes a ring of extreme roughness that is used by a spin bowler to achieve a similar effect (generating different air pressure on different sides) and generate a curved ball. That's why they do all that curious polishing of one side on their trousers. Must be similar for a baseball pitcher. And if anyone ignorant of cricket or baseball finds that all a bit far-fetched, then watching over-the shoulder TV pictures of Shane Warne in action some years ago was a real eye-opener for me and anyone else with an interest in ballistics who was fortunate enough to see it. The bamboozling effect on the batsman was (wicket-)shattering.
If you can read German, then I recommend the volumes on ballistics by Beat P.Kneubuehl. There must be something similar in English. Not light reading, but it gets your ballistics knowhow off the anecdotal level pretty steeply.
Sorry if that was a bit involved, but you did ask!
Quote:
Originally Posted by Peter Laidler
But how are the sights adjusted? You may remember I once posted a photo of a machine gun sight that was identified as being from an M2, and that sight leaf had a very noticeable slant.
Here it is:
Attachment 36669-Attachment 36670-Attachment 36671
What does a Vickers backsight look like?
Quote:
Originally Posted by Beerhunter
I would be grateful for an explanation, as I still maintain that bullets have no memory. Without wishing to cause the slightest offense, "well-known" is not a scientific argument.
Not sure if this is relevant but I was discussing the use of optics on Machine guns with a German NCO from the 1980s Bundeswehr. He indicated the optics on the MG1/MG3 on the tripod was located to the left of the gun and that the gun was zeroed at close range with the point of impact being somewhat to the (right/left?) of the point of aim. The spin of the bullet would result in the actual group being on target at some long distance, but what that range was I do not recall. I seem to recall the maximum distance the MG was optically sighted for was 1600 meters or something like that. In any case if I understood him correctly the sighting of the mount/optics took into account some kind of lateral drift of the bullet at long range.
I also seem to recall that the left hand twist of the Lee Enfield and firing of the rifle in the southern hemisphere during the Boer War was the reason for the zero issue that is contained in both Reynold’s book and Skennerton’s book on the LE. I think the problem there was the rifles had some left drift at long range in the southern hemisphere which meant the Brits were putting their bullets off of the aimed target. This difference was related to the Corolis force if I recall correctly, which is in opposite directions in the northern and southern hemisphere.
http://en.wikipedia.org/wiki/Coriolis_force
(Jump to section on inertial circles halfway down page and read on from there)
Now perhaps the Aussie sniper who was firing his rifle in the northern hemisphere was referring to some slight lateral adjustment that had to be made for the difference in shooting a rifle zeroed in Australia (southern hemisphere) and a rifle shot in Korea ( northern hemisphere) at long range.
Quote:
Originally Posted by Frederick303
Careful, careful! This can rapidly slide back down to pub anecdotal level again, just as our brain cells were getting nicely warmed up!
If IF IF there is anything at all in the Coriolis idea, which seems to have been around as long as people have watched water going down the plughole, then any effect would depend on the direction in which you are shooting. And I have heard quite a lot of B-S over the years, but never that someone's rifle had a POI that altered if he changed the direction in which he was shooting.
Maybe I have just led a sheltered existence, or maybe all ranges have the same orientation. But combat is certainly not neatly arranged to be in the same compass direction as range practice, so even if the effect did exist, any built-in compensation would be 5/8 of f.a. use in practice, to use a British engineering term.
Peter,Quote:
Originally Posted by Peter Laidler
Am I missing something here? How is zeroing at 300 doomed to failure at any other distance?
If the scope is off set to the left of bore by 1 1/2" then a point blank shot would strike the target at 1 1/2" to the right of the point of aim. It would then coincide at 300 before moving on to strike the target 1 1/2" to the left of point of aim at 600. The scopes of the day were only calibrated up to 600 anyway and click stops a luxury that wouldn't be seen on Brit scope until the advent of the No32. One things for certain once set you certainly wouldn't want to beggar about with the deflection setting on a SMLE Sniper with the possible exception of the Whitehead / A5 combo.
Until I can remember where I've seen it recorded I'll bow to Roger's black and white info in the PAM:surrender: but I still think the 300 zero is feasible.
BTW??? The distance between trenches and anything else is academic. The only thing he's concerned with is distance.:confused:
My brain's hurting too now. time for nightcap I think:cheers:
Cheers,
Simon.
Quote:
Originally Posted by Simon
...And, since the left-hand rifling will produce a leftwards spin drift - why, it will indeed tend to bring the bullet back on course. Whether or not the spin drift effect is sufficient to curve the trajectory so much that it actually crosses over the direct line of sight again is a matter of conjecture - or rather, experiment. But since the spin drift depends on the ballistic characteristics of the bullet, the effect would also be dependent on which type of bullet is being used.
So the interesting effect cited at the start of this thread could really arise - with a rifle having left-hand rifling AND a scope offset to the left, AND zeroed truly (POI = POA, no offset aiming) at some intermediate range, AND using a specific bullet.
Does this all prove that left-hand rifling is superior to right-hand for offset scopes used over a wide range of distances? I suspect so, but don't want to stop anyone else chiming in on this most interesting thread. All soberly thought-through opinions are welcome. And a few measured facts would be nice, too!
I once found a free ballistics calculator that took into account both spindrift and the Coriolis effect. I can't find it now and I don't remember much about it other than it made my head hurt.
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Originally Posted by Frederick303
That sounds to me like a very fancy excuse for poor shooting, after the Boers had demonstrated that their 7x57 Mausers were ballistically superior.
Then why did the the Brits resight their rifles. You can not hit a target if the sights are not on.Quote:
Originally Posted by Patrick Chadwick
This thread is very interesting. My thoughts are more to the offset being in the verticle not the horizonital. If this is the case the sight is not altered there would be two points or crosses in trajectory.
Having played with a Patt 18 i would have picked a mid point zero of no more than 18 inch rise and fall and locked the scope never to move it again. To increase the range aim off (up)
Exactly Bindi2- the british were sending teir MLE's out very poorly sighted and I just pulled my MLE out to confirm there's no way to adjust front or rear for "windage". Needless to say, the Boers had well sighted rifles. On the subject of drift we shouldn't forget about the wind. Labudda and Skennerton provide one example (page 13, Accurizing and shooting Lee Enfields): "fresh Wind blowing from 2 o'clock....at 600 yards.....=42 inches allowance". Totally overwhelms spin-drift and the coriolis effect. Here in Alberta with a good Chinook blowing in from the west and a WW1 sniper rifle with scope offset to the left (zeroed at 300 yards) and shooting to the north, the bullet would cross to the left of the line of sight at 300 yards, then arc out further left before being carried far back to the right by wind. The wind here is about as constant as gravity so if you shoot at a north directed range you might see consistant behavior.
Ridolpho
First of all, correctly it is called the Coreolis Effect. That's 'Effect' and not 'Force'. Secondly, it effects major masses such as high and low pressures systems in the atmosphere and ocean currents. It is why low pressure systems spin clockwise in the Southern Hemisphere and anti-clockwise in the Northern Hemisphere. It does not cause the water in the loo to spin a given way despite common belief.Quote:
Originally Posted by Frederick303
People speculating that the Coreolis Effect could or would cause a bullet to move differently in north of the Equator than it does south of the Equator that causes me to believe even more that the whole story about .303 bullets 'crossing over' is speculation turned gossip turned 'gospel'.
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Originally Posted by Beerhunter
Quote:
Originally Posted by Patrick Chadwick
The compensation would be the tendency to have a larger vertical muzzle deflection with lower velocity rounds than high. At "close" ranges the slow bullets actually hit higher than the fast. My No.1 Mk.V displays an extreme version of the phenomenon.
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Originally Posted by Ridolpho
I absolutely agree. Personally, I have managed to land shots in the black at 1000 yards - on the neighbor's target! :o
I make the feeble excuse for myself that I was firing a BPCR with about 2.5 seconds flight time in a situation on a hogback hill with the wind corkscrewing unpredictably from left to right.
But the competition was won by a first timer! There is such a thing as natural talent, and he had it.
From my experience of not being able to do it, and observation of those who can, I reckon that the abilty to "read the wind" and aim off accordingly is far more important in long-range shooting than all the other more-or-less subtle effects that we have been discussing. How many Tommies had undergone any serious training in this art?
But returning to the original conundrum: I posited that the leftwards spin drift of a left-hand rifles barrel could, partially at least, compensate for the rightwards angle (relative to the barrel axis) of a scope with an offset to the left, beyond the range at which the scope had been adjusted for POI = POA.
Whether that is to be regarded as a very clever piece of Enfield engineering or a plain fluke will probably depend upon how cynical you are feeling at the moment.
Any comments on that, anyone?
Patrick a plain fluke, cynical not really the knowledge of long range shooting in general, the change over from black powder to cordite new rifles etc was at the begining of where we are today. The scope hight above the bore today causes similar problems for the new unwary shooter. How do i know this, looking for PBR with a new combo then need to know the adjustments out to 1000yds + by 100 yd increcements. The range books will only put you on paper maybe.
Quick OT note on the Shane warney thing. Note with this it is not the SPIN of the ball when shane warne bowls that causes it to drift. He spins it anti clockwise as it goes towards the batsman and therefore if it were the spin it would actually drift to the left (or off side) as it travels. It is the spin of the ball which keeps the seam in a constant position relative to the air it encounters in teh diretcion it is bowled in. ie if viewed from above at any point down the pitch the seam would be at roughly 60 degrees across the pitch. it is this constant position on the seam relative to the airflow which creates a 'laminar boundary layer' and less air pressure on one side of the ball, thus the slight curve in the air. The spin helps it dip. Further note as an Englishman and leg spinner myself, but Shane Warne was bloody fantastic to watch, though obviously a crim and a scoundrel of the highest order.
Haven't read the whole thread, so maybe this has been said already, but perhaps what the original comment alluded to was the well known ability of the No1 and the No4 to "compensate" through the flexing of the action. This led to smaller vertical than horizontal dispersion at that sort of range, and so the horizontal dispersion would seem oddly greater than the vertical dispersion, when in fact the horizontal dispersion was quite normal for that range and ammunition, but the vertical dispersion was unusually small.
Sometimes it's all how you look at it.
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Originally Posted by newcastle
Thanks for the explanation. Not quite the same cause, but the same effect - lower pressure on one side.
Now I realize this is getting awfully close to being off-topic, but how do baseball pitchers produce the asymmetrical pressure for a curve ball?
Warney a crim and scoudrel no way, larrikin yes , spinner yes and very good . Dont know if he had a clue about Enfields though
I thought the biggest problems to over-come for Aussie bowlers was ground effects & friction :)
That was a bit grubby wasnt it, even for an Aussie but then we were playing the kiwis so any thing to win.Quote:
Originally Posted by 5thBatt
Our biggest problem is getting free beer out of Demo.:beerchug:
There is action at the station D day has been named the day will be warm and the BEER cold
That makes a lot of sense to me.Quote:
Originally Posted by Surpmil
BTW, thank goodness several others have chipped in on the Lee-Enfield action's compensation phenomenon. It was starting to look as though it was only "well known" by me.
Major EGB Reynolds makes a comment on pages 137 & 138 of his book "The Lee-Enfield Rifle" about how the Lee Enfield action "compensates".
Here is what Reynolds says on page 137 involving the No1 MkVI trials
"The question of whether the Mark VI rifle "compensated" in the same way as its predecessors was the subject of trials which, unfortunately, were never brought to a definite conclusion. When a rifle is fired, the barrel vibrates in both the vertical and horizontal planes, the vibrations being largely due to friction between barrel and bullet. A rifle is said to "compensate" when, due to the barrel vibrations in the vertical plane, bullets of higher velocity leave the muzzle on a lower line of departure, and those of lower velocity leave on a higher line of departure. The distance at which the trajectories of the two bullets will cross is called the "compensating range" of the weapon.
The following quotation from the Text Book of Small Arms, by permission of the Controller of Her Majesty's Stationery Office, describes the "compensation" of the earlier Lee-Enfield Rifle: "The Lee-Enfield Rifle vibrates in such a manner as to reduce the difference in height between the points of mean impact of ammunition with different velocities. for example, a Lee-Enfield Rifle fired with ammunition giving 2,235-f.s. velocity, shoots 12 ins. lower at 200 yards than with ammunition giving 2,000-f.s. velocity. At 390 yards range the points of impact with both classes of ammunition are at the same height. At 1,000 yards the 2.235-f.s. ammunition shoots 7 ft. higher than the other. We see, therefore, that the bullets of the high velocity ammunition leaves the barrel when the muzzle is at a much lower point in its curve of vibration, and therefore shoots low at 200 yards, but their trajectory being flatter than that of the 2,000-f.s. ammunition, it crosses the trajectory of the latter at 390 yards range, and keeps above it at all other ranges..................."
I had a Steyr ssg 69 , Austrian sniper rifle frrom 1970. It is locked rear, also. But out to 900 meters it shoots well, no lateral dispersion : it guaranted sub moa accuracy with his own ammonitions.
I think the same principle will apply to our loved Lee Enfield.