An Odd Characteristic of the SMLE

[Bruce_in_Oz]

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.

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Roger Payne]

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

[newcastle]

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.

[Peter Laidler]

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!

[Simon]

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!

Peter,

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 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.

My brain's hurting too now. time for nightcap I think

Cheers,

Simon.

[Patrick Chadwick]

It would then coincide at 300 before moving on to strike the target 1 1/2" to the right of point of aim at 600.

...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!

[Frederick303]

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.

[Patrick Chadwick]

This difference was related to the Corolis force if I recall correctly, which is in opposite directions in the northern and southern hemisphere.

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.

[Patrick Chadwick]

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.

That sounds to me like a very fancy excuse for poor shooting, after the Boers had demonstrated that their 7x57 Mausers were ballistically superior.

[Bindi2]

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.
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)