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Okay, first of all my Model #4 Mk1 rifle's head space is okay (gunsmith inspected). However what do I do when the headspace gets to big when the bolt head is currently a #4? Do I add a spacer? Try a different #4 head? Rebarrel? Any suggestions? Thanks.
Firstly I doubt you will increse the headspace enought to worry about it unless you plan to shoot 10s of thousands of rounds.
Secondly - are you sure its a size 4 bolt head ? Of all the folks on this forum I have only ever heard of 3 size 4 bolt heads being seen (EFD had two). Can you post a pic of it ? If it is a size 4 its probably worth more than the rifle.
Measure the bolt head true size :
https://www.milsurps.com/images/impo...surement-1.jpg
What size is it ?
About a year ago I did a survey of over 100 bolt heads to see if the "size" corresponded to the actual dimensions - to some extent it did but it was possible to get (say) a size 1 bigger than a size 2, or a size 2 bigger than a size 3 and so on. The actual results are :
*Size 0 = 0.620" - 0.631"
*Size 1 = 0.622" - 0.635"
*Size 2 = 0.630" - 0.640"
*Size 3 = 0.632" - 0.640"
If you ever do need a new bolt head then maybe you could use a lower size and actually get tighter headspace.
* These meaurements were taken by different people using different verniers / micrometers so there is potential for errors.
Another way of reducing the headspace is to try different bolt bodies as they can 'compress' (reduce in length) due to continued recoil and wear at the mating surface with the bolt head. A 'new' bolt body may be 'longer' than your 'old' one.
Another thing to watch for is bolt head over rotation :
https://www.milsurps.com/images/impo...eadWear1-1.jpg
https://www.milsurps.com/images/impo...eadWear3-1.jpg
https://www.milsurps.com/images/impo...eadWear2-1.jpg
Over-rotation Pictures Courtesy of Ed Horton
There was a thread some time ago about 1950's trials aimed at establishing the viability of a higher size bolt head. It was deemed that............ anyway, someone will repeat the findings but the long and short was that if you can't get CHS with a No3 bolt head and a new bolt/bolt head, then it indicates a worn body
CHS - Body and bolt wearQuote:
Originally Posted by Peter Laidler
Posted By: Peter Laidler
Date: Mon 28 Apr 2008 9:17 am
You should all read and re-read this if you have ever thought about CHS, body wear or fitting a new bolt, especially in response to the recent thread about the matter.
I was having a chat to one of the most senior examining Armourers at a huge Base Workshops at Warminster a few days ago. Long retired, he was a 1930's apprentice and one of the very strict examiners. I was asking him about chroming bolt heads to get longer life out of heads bolts and bodies when he reported back something that was VERY interesting.
He said that during the mid 50's, there was a plan mooted to make a No4 size bolt head available so as to decrease the number of old wartime/tired/just plain worn out rifles being condemned as unfit simply because of insufficient CHS. The alternative was to increase the MAX CHS to .078".
He was involved in this project as the research Officer, so was in from the start. The PROBLEM was that once the BOLT, Inspectors, Gauge (a calibrated slave bolt used to test wear) plus a calibrated No2 bolt head (No3 not permitted at Base/Factory don't forget) had been inserted into the inspectors gauge bolt, then making a further bolt head available was palliative and not a cure because these simple tests indicated that it was the BODY that was worn and not the bolt or the face of the barrel. And thinking about it, while it's obvious really, it's absolutely correct!
Another problem they encountered was that with the speed of wartime production, the induction hardening of the bodies was at best, mediocre, and at worst, sometimes virtually non existant. The hardening sometimes had no depth and it was tested at Base Workshops by the old IZOD impact test method. Apparently, all manufacturers were as bad or good as each other including Savage and LB (I bet that has shocked a few of you who were probably lead to believe that some makers were 'better' than others......)
I spoke about resurfacing bolts but he just shook his head sternly and wagged his finger as if to say. 'No, it's the BODY that's worn beyond the point of no return and once the hardness is gone, then there is no cure.'
There, that's straight from the horses mouth and it doesn't come any clearer or louder than that. If you cannot get CHS with BOTH bolt lugs bearing evenly using a No3 bolt head, THEN trying a new bolt, then it is the BODY that is finished. Sorry about that.....................
I found this on a Golf Course, it was very strange day everyone was yelling Foooour! :rofl:
https://www.milsurps.com/images/imported/deleted.gif
I came across a bolthead stamped 4 earlier this year, only one I have ever
seen, used it recently to headspace a tidy No4 Mk11! Was a few thou longer than a 3, used it because it didn`t overthread. It didn`t have any markings on it so I assume it was a commercially made one? Australia? Does anyone out there know?
No4 boltheads are a bit of an enigma. Maybe someone ought to do a steel analysis on one and compare it with a bog standard No 0,1 or 2.
I say this because it can't/won't be a factory made bolt head (?) because FTR/Base Workshops would reject bodies that wouldn't CHS on a 0 1 or 2 bolt head using the GAUGE, dummy bolt, armourers. And there was never such a beast as a No4 bolthead in UK or NZ military service
Can anyone identify any other marks on a No4 bolt head? What about a visible proof mark?
I have two.
One is brand new, .642 in length. Marked with an "M" and the broad arrow.
The other is "well used", .642 long. It has an "F" or "E" and "2??" in a box".
A search through 3-400 units came up with only two of the beggars.
If you want to learn more about the very basics of "headspace", Parashooter published an excellent teaching article in the Technical Articles for Milsurp Collectors and Re-loaders(click here)Quote:
Originally Posted by Timmer
Headspace 101 for .303's (click here)
Regards,
Badger
Got to agree on the bolt heads. If headspace is correct now, you are NOT going to be able to shoot the rifle enough to change it.
Badger, please consider replacing that version of "Headspace 101 . . ." with the current iteration, which contains some added information and removes the controversial lubed-case approach. (You might also remove the obsolete e-mail address. I have a new one I don't post but can be reached through this board's PM feature.) Thanks.
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Several generations of American shooters have been convinced by bad information that something mysterious and scary called "headspace" should be checked and re-checked on almost any surplus rifle, especially Lee-Enfields. The truth is less interesting but still worth knowing.
Stripped to its essentials, with a rimmed cartridge like the .303, headspace is simply the distance between the front of the bolt and the back of the barrel. It's the space where the "head" (rim) of the cartridge fits when the rifle is loaded.
https://www.milsurps.com/images/impo...eadspace-1.gif
Since there has to be some room to allow for varying rim thickness, the headspace is normally a bit more than necessary - giving what I call "head clearance", a little extra space so the bolt can close easily, even on the thickest rim allowed.
In addition, Lee-Enfields and their ammo were often made with a fair amount of space for dirt, mud, snow and other battlefield debris between the chamber and the cartridge's body and shoulder ("Body/shoulder clearance"). Since the cartridge is controlled by its rim, this clearance doesn't do any harm (except to handloaders who insist on full-length sizing).
When a full-power .303 cartridge is fired, a whole string of events occurs.
https://www.milsurps.com/images/impo...estretch-1.gif
1. The firing pin shoves the case forward, rim against the breech.
2. The primer detonates. If it's not heavily crimped in place, it backs out, shoving the bolt and barrel as far apart as it can.
3. The thin, forward part of the case expands to fill and grip the chamber while the bullet moves out of the case and down the barrel.
4. The solid case head can't expand and grip the chamber, so it moves rearward, re-seating the primer, stretching the case walls just forward of the head, and stopping when it hits the bolt face. (In rear-locking actions like the Lee, the bolt and receiver also compress/stretch to add a little more movement. The higher the pressure, the more they move.)
5. If (and only if) the amount of head movement exceeds the elastic limits of the case, the cartridge separates into two pieces.
New cartridge cases can normally stretch a lot before breaking. Even with a minimum rim .054" thick and maximum "field" headspace of .074", the resultant .020" head clearance is well within the limits of new brass and it's very unlikely a new case will separate even if the headspace is somewhat more than the field maximum (which is pretty rare).
OK, but if one does separate I'm in deep trouble, right? Not really. It seems the short "cup" left behind the break is pretty good at keeping most of the gas where it belongs. Here's a demonstration -
First I took a case that had been reloaded with heavy loads enough times so it was stretched near breaking.
https://www.milsurps.com/images/impo.../303sep1-1.jpg
I loaded it with a 180-grain bullet and 40 grains of 4895 - a reasonably stiff charge about 2 grains under "maximum" - and fired it in a much-abused Savage No.4 with a clean sheet of typing paper wrapped around the receiver.
https://www.milsurps.com/images/impo.../303sep3-1.jpg
When I opened the bolt, the separated head extracted. (The front piece of the case fell out when I happened to turn the rifle muzzle-up while removing the paper.)
https://www.milsurps.com/images/impo.../303sep2-1.jpg
The sooty paper shows where some gas escaped. No rips or holes, just a little soot - and only where the bolt meets the barrel. Had I been shooting from the shoulder and wearing glasses, I probably wouldn't have noticed the leak at all.
The point of all this is that excess headspace, even a bit beyond normal limits, isn't the terrible danger we've heard so much about. It's not a good thing for consistent ignition or long case life (although handloaders who neck-size or adjust F.L. dies carefully can control this) - but it's not a disaster waiting to happen.
Unless you're consistently getting broken cases when firing new ammo or brass, there's not much reason to be worried about headspace in these sturdy old Lee-Enfields. Relax and enjoy!
Handloading
If you handload for a .303 with generous headspace, there's no need to mess with bolt heads - changing the rifle's clearances to yield longer case life. You can control head clearance simply by changing technique.
When you fire a new case for the first time, use an improvised spacer ahead of the rim - anything from a precision metal washer to dental floss can work to hold the the cartridge head firmly against the bolt face and eliminate or reduce stretch even if head clearance is significant. Another way of accomplishing the same end is to use a bullet seated out far enough to jam into the lands, "headspacing" on the bullet instead of the case. Such techniques are useful only if the rifle has excess headspace. With normal headspace, initial stretch isn't enough to worry about.
https://www.milsurps.com/images/impo...spacers2-1.jpg
After you've fire-formed your new cases they will fill the chamber fully, stopping on the shoulder just like a rimless cartridge. If you neck size, you'll have zero "headspace". If you have to full length size, adjust the die so the cases chamber with just a bit of resistance in the last few degrees of bolt rotation.
Finally, don't try to turn a .303 into a magnum. Keep the pressures below the limit and you reduce the small amount the bolt and receiver compress/stretch on firing in a rear-locking action.
With these techniques you can make your .303 cases last for dozens of loading cycles, even if your "gauge headspace" is well beyond the .074" field spec.
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To demonstrate how we can control head clearance using only the shoulder, I filed off the rim of a once-fired Remington .303 case. After adding an extractor groove to fit a Mauser-size shellholder, I neck-sized, reloaded and fired this case 19 more times.
https://www.milsurps.com/images/impo...imless20-1.jpg
The load was a 180-grain jacketed soft-point over a lightly-compressed charge of IMR 4350 (giving an average velocity of 2310 fps for the 19 shots and listed at just under 39,000 CUP in my IMR data booklet). The test rifle was a 1943 Lithgow S.M.L.E. Mk.III*. 20 shots was enough for a practical test, I sectioned the case to examine the web/body junction area where thinning normally occurs.
https://www.milsurps.com/images/impo...mlesssec-1.jpg
This case, fired 19 times with no rim, has not stretched or thinned at all. I'm sure it could have continued for at least another 20 of these moderate loads.
It's clear to me that the .303's shoulder, alone without help from the normal rim, is entirely adequate to maintain "headspace" when sized in a way that preserves the shoulder location. Those handloaders who experience poor case life with neck-sized handloads should look for other factors to explain premature case failures. The most likely source of trouble is high pressure. More pressure means more action flex and that means shorter case life.
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Just to demonstrate that there's nothing new (except computer animation), here's a page from a 1937 book I found online several years after first posting "Headspace 101 . . ."
https://www.milsurps.com/images/impo...amoregif-1.jpg
The British Enfield rifle has gotten a bad reputation in regards to headspace that it does not deserve, American made SAAMI designed cartridges have thin rims, small base diameters and are designed for chamber pressures below 43,000 CUP.
These American made cases were designed for less headspace and lower pressures levels than the military Enfield was designed to operate at. Privi Partizan cases have thicker rims, and are at least .010 thicker in the base web area than American made cases and remind me of military designed cases which are much thicker in the base area than commercial cases.
Below is a Privi case on the left and a Greek HXP case on the right, the Privi case has a larger and thicker base diameter than the Greek HXP cases and looks far different after being fired in an Enfield rifle. The HXP case pictured after checking over 500 once fired HXP cases did NOT thin or stretch in the web area at all.
The Privi cases remind me of my Lake City Match grade 30-06 cases and are built “Ford Tough” (the Winchester cases are built like a Chevy and fall apart after just a few reloadings):rofl:
https://www.milsurps.com/images/impo...privihxp-1.jpg
Do not misjudge your headspace by looking at your fired cases, headspace is actually governed by the cases you shoot and not your military specifications for headspace of your Enfield rifle. (You don’t use 13 inch tires for a Toyota on a 18 wheeler truck)
The 2002 Canadian No.4 Enfield manual has headspace settings for what I believe is the use of commercial ammunition in their Canadian Rangers Enfields, AND this is for firing the case once and not reloading it.
Headspace is governed by the cases you are shooting and not the specifications written in the British military manuals.
Case in point, below is the Canadian No.4 headspace settings published in 2002.
I read this as:
.064 GO
.070 NO-GO
.074 FIELD
https://www.milsurps.com/images/imported/deleted.gif
Below is a Winchester case and it is .020 thinner in the web area than the Privi case below it.
https://www.milsurps.com/images/imported/deleted.gif
Privi case built Ford tough :D
https://www.milsurps.com/images/imported/deleted.gif
Also this idea came from our old Jouster forum and was submitted by a Canadian member, he used rubber o-rings to fire form his cases which pushed the cases up against the bolt face and prevents case stretching and thinning in the web area. After the first firing or fire forming the cases then headspace on the shoulder of the case.
https://www.milsurps.com/images/imported/deleted.gif
https://www.milsurps.com/images/imported/deleted.gif
Below is a factory loaded Winchester case that was fired in my 1943 Maltby with the headspace set at .067, this case thinned and stretched .009 (nine thousandths) in the critical web area. The head gap clearance or the distance from the rear of the case to the bolt face on this case is .009(nine thousandths) how much do you think the case would thin and stretch if the headspace was set at .074?
https://www.milsurps.com/images/impo...IMGP4523-1.jpg
https://www.milsurps.com/images/impo...IMGP4521-1.jpg
The quality of your cases makes all the difference in the world when you are reloading, if you do not reload then headspace set at .074 should not cause any problems in a properly maintained Enfield rifle.
Please note this post is not intended to take anything away from Mr. Parashooters very well written headspace 101 or insult Mr. Parashooter in any way.
( I hit the post button and saw Mr. Parashooter was here before me and wish to make my posting clear to all)
Roger that .... :thup:Quote:
Originally Posted by Parashooter
Will do over the weekend as I'm currently traveling on business....
Thanks for the heads up...
Regards,
Badger
I agree with almost all of the above except...
Those "tricks" (I liked the use of monofilament line) will work to a point, and will at least temporarily prevent case stretching and separation. But if the rifle is fired enough, a point will come where excess headspace will allow the case to back out of the chamber far enough that the thinner part of the case will not be supported, and the result will be damage to the rifle and possible injury to the shooter. The recommendations only delay, they do not prevent, severe damage.
If the locking lug seats in the receiver (body) are so badly battered that they result in excess headspace to the point of case separation, it is time to retire that receiver. Any of those "techniques" will only delay the inevitable and give the shooter a false idea that he has "fixed" the headspace and can continue shooting the rifle indefinitely . He might find out the hard way that the "fix" doesn't work.
Jim
This is why I said headspace is governed by the type cases you shoot and not the rifle and I fully understand what Jim K is saying about the case being unsupported in the rear with far too much excess headspace.
The case below is bulging past the diameter of the camber and the next step is “explosive case separation.”
https://www.milsurps.com/images/imported/deleted.gif
The red and yellow areas below are the areas of highest stress.
https://www.milsurps.com/images/imported/deleted.gif
A "normal" case after firing.
https://www.milsurps.com/images/imported/deleted.gif
The case and its construction determine how much stress and pressure it can withstand, below is a new unfired Remington case in a Wilson case gauge. The gauge is used to set up headspace on resizing dies, the cases pictured are resting on the shoulder and not the rim of the case.
https://www.milsurps.com/images/imported/deleted.gif
Below is the Privi Partizan case and the shoulder of the case is in the correct position, the rim is over .004 thicker and the case wall thickness is .020 thicker than the Remington case.
Which cases would you rather use and reload?
https://www.milsurps.com/images/imported/deleted.gif
That's conceivable, but the rifle has to be very badly buggered for the case head to back out far enough to even approach the front end of the solid head. As can be seen in the image below (of once-fired Berdan and much-fired Boxer cases), a whopping .060" excess (beyond the .070" "SAAMI field" limit) gets the case only as far as the end of the primer pocket at .130" from the bolt face. Something has to be terribly wrong for a Lee-Enfield to "develop" that much excess - lugs filed down, barrel backed out, receiver broken, burned in a fire, welded, etc. Lots of ways to screw up a rifle, but not likely to happen from several lifetimes of normal firing, I suspect.Quote:
Originally Posted by Jim K
https://www.milsurps.com/images/impo...headsec2-1.jpg
Mr. Horton - Am I suffering from an "optical delusion" or did you measure those case walls at a different distance from the base?
https://www.milsurps.com/images/impo...303walls-1.jpg
What results would we see if compared at the same place?
Mr. Parashooter
A chain is only as strong as its weakest link and the case will thin and stretch at its weakest point, the Winchester case pictured was measured where the case were separating in my 1943 Maltby.
As you can see below the case separated above the maximum expansion area at the base of the case
https://www.milsurps.com/images/imported/deleted.gif
I take the measurements at the transitional point of the case just above where the case starts to thicken rapidly BUT this is a mute point because the base of the case is shaped differently on each case (the bowl at the base) and effects the point where the case would separate.
I’m guesstimating where the weakest link of the case is at.
https://www.milsurps.com/images/imported/deleted.gif
https://www.milsurps.com/images/imported/deleted.gif
https://www.milsurps.com/images/imported/deleted.gif
https://www.milsurps.com/images/imported/deleted.gif
https://www.milsurps.com/images/imported/deleted.gif
Below you can see that these .308 cases fired and reloaded to destruction did not separate at the same point on each case and these were fired in the same rifle with a commercial chamber that was smaller in diameter and had LESS headspace than a military 7.62, BUT these cases were each constructed differently and each case had its “weakest link”.(Therefore measuring each case at the same exact point is meaningless)
https://www.milsurps.com/images/impo...308fail2-1.jpg
https://www.milsurps.com/images/impo.../308fail-1.jpg
Thanks, Ed. I think your latest set of pictures, showing the W-W and R-P cases at ~.030", might be a more accurate reflection of the situation than the one showing the W-W case, farther forward, at .020".
Prvi may have a proclivity for heavy walls. They made the GRAF case shown here - much thicker sidewalls (but thinner web) than the W-W .348 -
https://www.milsurps.com/images/impo...lcasesec-1.jpg
Have you sectioned any of the Prvi .303's?
Parashooter
I bought new two boxes of Privi Partizan .303 ammunition and fitted a extra No.0 bolt head to my 1943 Maltby, this gives me two bolt heads and two headspace settings to test fire the Privi Partizan ammunition. One at .067 and one at .074 and then I will section the cases for photo purposes with the case stretching visibly showing.
You can’t at this time buy empty unfired cases from Privi Partizan, but I’m going to test them against new Remington and the Greek HXP cases and see which one holds up the best in testing.
What amazed me was I purchased 500 once fired Greek HXP cases from Brian Dick and checked each one for stretching and thinning in the web area on my RCBS Case Mastering Gauge, NOT one case had ANY thinning or stretching. (None, zero, zip)
I have these cases ready for testing also and plan to photograph them also after test firing them, it appears the not all .303 cases are made to the same specifications, it is also my understanding that five grades of brass are used to make American cases and I think our .303 cases are made from the same grade as our 30-30 and 30-40 Krag.
Below, Greek HXP, Remington and Privi
https://www.milsurps.com/images/imported/deleted.gif
The determination of a potential problem is not the thickness of the rim but the depth (or height if you prefer) of the base. The further heavy brass extends into the case, the better the case will stand excess headspace. And that is part of the trouble here. The assumption by some seems to be that if case brand "X" will not burst with a headspace of "Y", then a headspace of "Y" is safe, no matter what those silly old gauges say.
Headspace is actually of more concern to the military than to civilians. If a case separates in a civilian rifle, the worst that will usually happen is a trip to the gunsmith or watching a prize deer depart for safer places. If that happens in a military rifle, the soldier may well be killed. But that does not mean that it can be ignored by civilians or that neat ways to bypass excess headspace are good ideas.
The Rifle No. 1 (incl. SMLE) has another area of concern. Due to its rear locking lugs, when subjected to high pressure, it will "spring", the receiver actually bending so the bolt head pulls away from the barrel breech. This happens in an instant and in most cases the receiver springs back and leaves little sign of what happened except a blown case, a ruined magazine, and usually a departed extractor. But some damage remains, and excess headspace is usually part of it. This does not happen (or I have never known it to happen) with a No.4, which has a stronger receiver.
Jim
So my 30-30 with its rear locking lugs never flexes.
The same for the 30-40 Krag rear locking lug never letting the action flex.
And the Remington 788 with its rear locking lugs must never flex even with the higher pressure.
Or is it just British rifles with rear locking lugs that flex.
I’m glad our “Superior American” rifles don’t flex when fired :rolleyes:
https://www.milsurps.com/images/imported/deleted.gif
(Did I tell you I like my Enfield’s Jim K) :super:
I'm reading Jim's post above and looking at the many pics of sectioned cases in this thread and thinking the headspace would have to be near .250" (a quarter of an inch) to allow the thick part of the base to be out of the chamber on firing.
.250" would be kind of on the high side. If you notice the yellow lines in the image below, they're marked with distances from the rear surface of the case.Quote:
Originally Posted by Son
https://www.milsurps.com/images/impo...headsec2-1.jpg
The thickest web here is only a tad more than .180", while the thinner ones are about .155". Still, a .303 rifle would have to be in very sad shape to have that much headspace.
It's always seemed to me that some folks on these forums enjoy emphasizing the dangers of excess headspace. I'm more inclined to believe General Hatcher:
". . . With good strong actions and moderate pressure loads, and especially if the shooting glasses are worn, this trouble is not particularly dangerous, but is annoying and inconvenient. Very little, if any, gas escapes to the rear, because the back end of the cartridge, which remains in the chamber, acts as a seal. In fact, it is just such short brass cups that the Germans have for years used as the breech seals in their heavy artillery . . .
". . . In my own experimental firing I encountered at least a couple of hundred such separations, and every one of my several thousand students had to experience and correct this situation several times and I never saw enough gas escape to hurt any one. . . "
"Our riflemen are used to measuring the headspace of their rifles by thousandths, and are prone to become very much alarmed if the headspace gauges two or three thousandths of an inch more than the normal maximum. This is a good safe attitude to take, but it is something like measuring cordwood with a micrometer. . ."
In a lifetime of shooting and handloading, I've had about a hundred case head separations (mostly from excess full-length sizing and refusing to discard worn-out brass). Like Hatcher, I've never felt even a trace of gas when this happens. And because I keep a "broken shell extractor" handy, it's never been more than a momentary inconvenience.
Head separation is more to do with poor quality brass, wrong measurement used in manufacture or resizing than headspace. The problem seems to com from one souce only and that is not the home.
I use No1s, 4s and 5s and i have had more failures in the later actions because of the brass used.
The measurements are meaningless if the cases are not manufactured from the same grade brass or brass of the same specifications, if someone can reload Greek HXP cases 30 times and a Winchester cases only lasts three firings someone is adding pot metal to the mix or American manufactures don’t know how to make .303 cases.
Tight headspace to me is making your American .303 cases last longer if you reload.
P.S. Bindi2, your two fingers must be faster than my two fingers but at least our fingers think alike. :thup:
Parrashooter- I'm a subscriber to the same logic that you demostrate so well in your postings. I'm always trying to convince new owners that they don't need to "get a bigger bolthead in case their rifle is out of spec next week", but should be able to fire another 5000 rounds before even checking headspace again. The problem is, they don't seem to want to hear that.
Jim K seems to think there is a direct corrolation between excessive headspace and burst cases. The thought that a body can flex enough to allow the thin walls of the case to get outside the chamber, and then to say "in most cases the receiver springs back and leaves little sign of what happened except a blown case, a ruined magazine, and usually a departed extractor".....Hmmm, cannot concede to that possibility.
One other thing that doesn't often get a mention, but was demonstrated so well in your posting, Parrashooter, is the Lee Enfield's ability to safely vent gasses at the rear of the chamber with little or no discomfort for the shooter. Congrats in getting that message across too! It shows the action to be one of the safest around if a case rupture does occur.
Along with yourself, Ed and Bindi, I agree ruptured cases and head separations are a handloading issue, down to use (and abuse) of whatever raw materials you have on hand and their ability to endure said use.
The "quarter of an inch" bit was to try to demonstrate that by the time the case was far enough out to expose the thin sidewalls, the bolthead was clear of the receiver ring, and the handle couldn't turn down into it's locking recess without already having serious damage somewhere, but that had already been said too.
As a point of interest I measured the base thickness of several HXP89 cases. They were all around .191". I knew they would be thicker, the case capacity of these is noteably less than all others I have checked.
I agree with you there Son. In all of my time as an Armourer, I only knew of two breech explosions with No4 rifles and I mentioned those on the Jouster Forum. And incidentally, they were nothing to do with CHS.
This thread started in relation to a No4 bolt head (or a No4 rifle....) and it was established many moons ago that of a rifle couldn't CHS on a No3 bolthead, thgen it was fit for scrap as the body was worn beyond the induction hardened locking surfaces.
Ed, I'm at a bit of a loose end tonight and tomorrow. Will you ask the girl on your header if she'd like a game of volley ball at my place tonight.
Said very respectfully: it's Basketball, Peter.
Unless that volley ball was painted to mimic the basketball paint scheme. ;)
I am delighted to know that it is impossible for an SMLE to flex or bend. But just in case you wonder what would happen should the impossible occur, here is a picture of the cartridge case. I also have the wrecked magazine.
Jim
Jim K
That case would have been ½ to ¾ of an inch outside the chamber when the sidewall of the case blew out which makes me think you had a delayed hangfire and the bolt was partially open. What is remarkable is you had an explosion at the rear of the case and an implosion at the front of the case. :yikes:
In order for the action to flex and move that much the bolt and receiver would have been completely destroyed. :crying:
The only other possibility I can think of is the cartridge case was struck by anti-matter at the instant of firing almost pulling the cartridge case into an alternate dimension. :rolleyes:
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Rumour has it that the DCRA target rifles had some #4 bol theads made prior to changing to 7.62NATO in the mid to late 50's. A #4 bolt head is not a standard bolt head.
In any case, like John says, if the headspace is ok, don't worry about it. However, if the bolt is closing on a No-Go, but not a Field, the headspace is on the high end of tolerance. Still not going to be an issue, but if it goes bad, the barrel will have to be removed and the threads set back by a smithy.
Setting the barrel back won't do anything, I'm afraid. The back of the barrel would still be in the same place. The problem is at the rear of the action. As Peter stated here earlier, and on the old board, it was judged by the MOD that by the time a No4 rifle requires a bolthead in excess of the No3, the hardened contact surfaces of the locking lugs on the bolt and receiver would likely be worn beyond servicability. This sentenced the rifle XX/BR = SCRAP!Quote:
Originally Posted by Sunray
Lets face it, do you keep repairing punctures in a tyre with no tread on it?
I really like that analogy.Quote:
Originally Posted by Son
Thanks for this great thread folks, it's quite an interesting read.
Learnin' Lou
If the existing bolt and a special test bolt head that is 0.640 long fails the .074 gauge a new bolt would be fitted.
When a new bolt and the test bolt head (.640) fails the .074 gauge test the rifle is sent for FTR, FR, overhaul, I do not know if the old receiver could be repaired or if it would be worth the cost of repair.
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Headspace FYI
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Sometimes the term “headspace” is meaningless :yikes:
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The 7.62 NATO is larger at the shoulder than the .30 is at the same point, so the shorter cartridge wedges into the chamber. I don't recommend firing any gun with the wrong ammo, but I once fired two clips of 7.62 NATO through a .30 M1 rifle just to show it could be done with no problems. The case is supported, but not the way it should be, on the shoulder.
Because of the shoulder, the 7.62 round is usually difficult to chamber, and nearly impossible in a bolt action rifle, but the M1 operating spring takes care of that nicely.
And all of that proves nothing about headspace so far as wear on the rifle goes. If the case could back up, it would, and could still stretch and still burst if headspace were really excessive. Gen. Hatcher reamed the chamber of a M1917 way out, and fired a .30 round, giving much the same result. He then fell into the same trap (very unusual for that gentleman) of confusing headspace with excess chamber length. Not the same thing.
Jim
Hi, Mr. Horton,
Exactly, that case was way outside the chamber when it burst, and the rifle had shown no signs of excess headspace. The cartridge was 7.7 SMI, dimensionally identical to the .303, for their heavy machinegun, and worse, had been sitting in the hot sun. I have no idea what the pressure was, but it must have been humongous.
There was no hangfire and the bolt was closed. In fact, the bolt head was broken and the extractor missing; the bolt had to be hammered open. (No anti-matter, either but then I might not have noticed.)
The rifle had been fired many rounds before that with British .303 with no problem, in fact I had fired several magazines from it, but was not shooting it at the time of the incident. Afterward, the rifle was checked and showed slightly excess headspace, but was fired with the British ammo (from a tie-down rest - the front stock was destroyed), again with no problems. That receiver sprung under pressure enough to let the cartridge back out, then sprung back. Yes, it sounds hard to believe, but it did happen, and I have been told that it is not unknown when someone loads the wrong powder or tries to make a .303 Super Magnum.
The owner decided to scrap the rifle because no one knew what damage the receiver had sustained.
Jim
P.S. That SMI ammo was sold as .303 British in a blue box containing 100 rounds. If you encounter any of it, I STRONGLY recommend not shooting it in a No.1 rifle. I eventually fired the other 99 in a P-14 and a Ross M10. Even with those strong rifles, high pressure was obvious, but without the sunshine and heat, not dangerous.
JK
Ok, could you please make something a little clearer for me here... If the bolthead was closed, the action sprung back enough to let the case out so it blew the side out, then it closed again, how did that case get back into the chamber? There's no way that would fit- The torn flap around the base doesn't even look like it was forced against the chamber, so the bolt must have been back about half an inch and still locked as you said you needed to hammer it open. Also, how could you check the headspace after the incident and compare it to the measurement from before? You said the bolthead was broken, so to fire it, a different bolthead must have been fitted. Wouldn't that most likely change the headspace?Quote:
Originally Posted by Jim K
I just had a closer look at the base of the cartridge. Even from this angle, you can see that the primer still has it's rounded edges- the first sign of overpressure is the flatening out of the primer into the recess left by the radiused edge. No such indicator here. This tells me it definately was outside the chamber before it went off.
Having trouble getting my head around this one...
I'll go with Mr Horton's hangfire theory- you said you were not firing the rifle at the time, maybe the bloke that was needed something else to blame other than his impatience for wrecking a good rifle.
Here's the pic of that case again... save going back to look at it.
SMI made normal .303 ball & tracer with a nitro fill - they didn't make any exotic high pressure loads. I'm not sure there are any military .303/7.7mm loads which are not safe in a No1 - they can withstand standard proof rounds that far exceeds anything any military ever used. You'd have to fill the case with something very silly in order to bust a rifle.
I'm with Son on this one. No rifle action "springs" open by 1/2" without the parts continuing to head in opposite directions.... That case clearly blew outside of a chamber and never went back in again. Thats either a hang-fire thats been opened too soon, or the safety lug is broken off the cocking piece - i.e. the pin was protruding as the bolt closed, and it fired the round before the locking lugs engaged.
Commenting on the rest of this thread: apart from locking lug wear (sometimes exacerbated by over-tight headspace....), there is no other way that Lee Enfield actions "grow" headspace. The action may or may not spring by a microscopic amount, but it does not permanently deform in any way. look at the empirical evidence: there are millions of Enfields out there that have been shot-out, re-barrelled and shot out again - yet they have remained in spec regardless. I have here an Envoy with a "0" bolt head: its last owner logged 9,000+ rounds on this barrel using only 155gn ammo (which the UK NRA dribbles on about being "too powerful for No4 actions"...), and yet the headspace almost too tight to gauge.
No one seems to agonise about Mosin boltheads like this .....
Permit me to apologize for my failing memory and correct a statement that I made about that "sprung" SMLE.
I have kept in touch with the owner of that rifle and he recalls the incident very well. He told me that the action did not "spring back" and that it couldn't have because the case (the one I pictured) was stuck in it. He did get the bolt out and the receiver did not appear broken or cracked, so he pounded it back straight and did fire it with a new bolt, but then took off all the parts and smashed it so it could not be used again. (Those guns were all of $9.95 at the time, so it was not a major loss.)
Again, my apology for the mis-statement.
Jim