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Discussion Starter #1
This one was a very, very, very remarkable thread in the old Military Mauser Forum. While its importance goes beyond the Italian field, we have seen headspace questions surface here too repeatedly, both with regard to 8mm carbines and with regard to ex-military and civilian 6,5x54 MS conversions, plus there is the same - somewhat aggravated - headspace issue with the M 1870/87/15 Vetterli-Vitali 6,5 mm conversions.

So, have a thorough look, read attentively, and form your own opinion. This controverse thread is *very* instructive, in my opinion:

* * *

Hitzy
Posted - 02/02/2006 : 6:01:39 PM
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So I see ALOT of threads where guys pass on milsurps because they don't pass their no-go guage they carry around in their pockets.........
I'm just wondering why the concern? I may be way off base here, but I load for nearly everything I shoot, and headspace in a CRF bolt gun is really no concern to me at all.
Seriously, what can happen? The cartridge head is held tight against the bolt face by the extractor on mauser actions. When the round is fired the shoulder expands to fill the chamber, and that's it, that's all that happens. People have mistakenly fired a .308 round in a 30'06 M1917 rifle (not suggesting it, very stupid and careless move)and nothing catestrophic happened. That's a 1/2 inch OVER a sammi .308 no-go guage, not just a couple thou......
The case does look like a 45/70 after but no head seperation occured, no case failure, no injury, nada.
The case head is solid brass with a tensile strength of 80,000PSI+, except of course for the primer hole. Which by the way IS something I do check on milsurps.....firing pin protrusion. I've seen exponentially more pierced primers shooting milsurps then I have ever seen case head seperations as a result of oversized chambers.
One of the methods used to fireform improved cartridges (ackly etc.) is to seat the bullet really long (minimum charge of course) so it contacts the rifling and pushes the case against the bolt prior to firing.
Anyway, I'm sure I will get flamed for such an "unsafe" suggestion...
which BTW is fine with me as I will most certainly be scooping up all those "unsafe headspace" milsurps......


mag
Posted - 02/02/2006 : 6:34:56 PM
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You are correct. mag



houstonfrank
Posted - 02/02/2006 : 6:52:06 PM
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Somewhat scarey but I agree that at least in my limited experience of the few times I have done it, nothing serious happened and the case did not separate.



Z71
Posted - 02/02/2006 : 7:02:46 PM
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Hopefuly thats all that happens! If headspace is too terribly out of whack the case head could and will separate from the case body. Then you get a face full of 50,000 psi gas that could blow your eyes right out of the socket! Probably blow the ammo out of the magazine, floorplate and all. Could detonate the other cartridges too, which would likely scatter the rifle.

GOOD LUCK!

A bolt action rifle is headspaced to certain specs. If the rifle is overly long on headspace it is a definate sign that some work needs to be done, or something is wrong. Suppose you got hold of a rifle with a soft bolt. May have been burned in a fire, or just poorly heat treated(could and has happened, actions too). The bolt will wear and set back pretty quick. Hopefully the gun will konk out before the lugs let go! The longer the headspace, the harder the bolt gets pounded. I personaly don't worry too much about headspace, most rifles are OK, and I have only bought one that had extreme headspace. But to continue to use a rifle you know is beyond field gage spec is asking for disaster. Kind of like driving on bad tires.



DocAV
Posted - 02/02/2006 : 7:45:03 PM
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The reason why a 7,62 Nato in a .30 -06 chamber works without undue danger is that the 7,62 Nato case actually "Crush headspaces" in the 30/06 chamber, the taper of the 30/06 Body being an interference fit with the body taper of the 7,62 Nato.
So on firing, the case is well supported (Body and head, both by the chamber walls and the bolt face; The neck and shoulders expand, giving Gas seal, so no sudden escape of gas occurs to cut through bolt face and chamber walls,, and after firing, the normal brass elasticity allows extraction to proceed...I have seen a Garand in 30/06 fire an entire clip of 308s without a hitch, the fired cases ended up like 45 Rimless magnums, but both cases and rifle were otherwise unharmed by this short excursion into madness.

It is only when the cartridge used in the wrong chamber is very much undersized and unsupported by either the chamber walls or the bolt face, that Problems occur (as in a 6,5 Italian cartridge in a 6,5 Swede Chamber... cartridge jammed in by Bullet engaging rifling, unsupported at shoulder, or body in chamber,allowing case to split and gases to exit via bolt face and magazine well; Further, the oversize Carcano Bullet jams in the rifling, leading to either a bulged or split barrel (Have seen a M38 Swede reduced to scrap metal this way; Bolt head cracked, magazine blown out,receiver ring broken away over extractor slot, barrel bulged and split under rear sight, woodwork shattered, and shooter missing three fingers... and the .268 Mil Carcano bullet still stuck in Bore down from split. Case was welded to Bolt face.

So, from a technical point of view, where the base of the case and the Body tapers/Shoulders match or interfere fit with the chamber, then the mismatch is not "TOO" Dangerous ( as in firing 7mm mauser in an 7,9mm ("8") Mauser chamber, or firing 7,65 Argy in a 7,9mmchamber, or even 6,5 Italian in a 6,5 Greek MS chamber; but any case where there is NOT this interference Fit, and the Bullet diameters are Nonmatching, is asking for a quick ticket to the Morgue.

The Golden Rule is : NEVER mix cartridges and chambers: all it takes is difference in Head-to-shoulder lenght to ruin your day...
The fact that the cartridge is held against the bolt head is a nonsense...there is tolerance even in the Mauser Extractor, and it does move back and forwards on its bolt retaining spring and even in its retaining groove on the bolt body. Sufficient to allow a gas blow-by.

Regards, Doc AV
AV Ballistics



Mike442
Posted - 02/03/2006 : 02:03:03 AM
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Even if the extractor does hold the case tight against the bolt face, if there is too much headspace, the bolt (and the extractor) can be slightly forward of its designed position when placed in battery, thereby leaving a slight gap between the bolt lugs and the lug recesses in the receiver. When the cartridge is fired, it can slam the bolt rearward resulting in very high impact loadings on the bolt lugs and receiver recesses. The wider the gap, the greater the impact. This is especially true if the chamber has a very smooth finish, thus making it more difficult for the case to grip the walls of the chamber. That's why a chamber should not be overly polished. Impact loadings can induce very high stresses. And it only takes a few thousands of inch gap to produce the impact loadings. My advice is don't try to out guess the system. If headspace was not important, gunsmiths would not pay so much attention to it when building up a rifle and there would be no headspace gauges in their shops.



MCQueenie
Posted - 02/03/2006 : 11:15:31 AM
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"I've seen exponentially more pierced primers shooting milsurps then I have ever seen case head seperations as a result of oversized chambers."

That's been my experience too.

"Hopefuly thats all that happens! If headspace is too terribly out of whack the case head could and will separate from the case body. Then you get a face full of 50,000 psi gas that could blow your eyes right out of the socket! Probably blow the ammo out of the magazine, floorplate and all. Could detonate the other cartridges too, which would likely scatter the rifle."

OMG!! ROFL!! Care to back ANY of that collection of bovine excrement with anything resembling fact? What you are describing is a head failure where the case head is cracked or blown out through the web and base exposing the bolt face to the full force of the propellant explosion. That has nothing to do with headspace. Have you ever even seen a head separation or had one happen to you? I have. Nothing REMOTELY approaching what you describe. Both that happened to me were not even noticed except for the next round not chambering. Which brings us to the point of headspace and the use of the field gauge by military armorers. FUNCTION. Head separations don't blow up firearms they render them inoperable...a condition not desired in combat. Field measurements are determined to be the length where head separations are more likely to occur so yes the firearm was removed from service. BUT it wasn't because the armorer was afraid it was going to BLOW UP. Here's a challenge to all you Headspace Horror Story guys...DOCUMENT JUST ONE INCIDENT where what you claim has actually happened. Just show us one case where "excessive" headspace and that alone caused the catastrophic disassembly of a firearm. Excuse me if I don't hold my breath while I wait.



richardwv
Posted - 02/03/2006 : 4:14:38 PM
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First, case head separation has fortunately become exceedingly rare as the quality of ammo has improved dramatically since the bolt action was first used with smokeless powder. Loose headspace increases the probability, which still remains fairly low. What happens when it occurs varies from rifle to rifle and event from event. Sometimes you have nothing more than a failure to function until the case remains are removed. Sometimes you can get hot gas blown where you'd prefer not to see it, like back down the bolt into your face. Despite all the hype on the superior gas venting of the M98 Mauser, the only rifle that did that to me was a M98 Mauser and it wasn't initiated by bad headspace, but by faulty ammo (S&B in .243).

All the hoopla about gas venting qualities of a given design was because case head separations and other case failures resulting in gas leakage were far more common when the designs were young. Shooters didn't wear shooting glasses back then either, so unlike my case where it trashed a nice set of glasses, it went into the shooters unprotected face. While the era is not known for OSHA like concerns for safety, the military was astute enough to know a blinded conscript was not a good thing.....hence the preoccupation with venting qualities and many retrofits to improve it.

Headspace is also an accuracy issue, which is why hand loaders neck size cases for match shooting, minimizing case flex/expansion when shot. A lot of people don't hand load and for them bad headspace means more case expansion and less accuracy than their rifle is otherwise capable of, whether or not any failure occurs. It also is harder on brass for those that reload but FLS the cases to fit any rifle in their collection, vice tying individual cases to individual rifles.

Bad headspace is not fatal, but it isn’t good either. If it isn’t too bad and you hand load by neck sizing only and tie the brass to a single rifle its affect on the individual might be negligible, but if you don’t do all of the above, passing on a rifle that is out of spec is sensible.



OldIronMan
Posted - 02/03/2006 : 4:57:22 PM
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The only type of headspace problem that can lead to a serious gas release as described above is if the increased headspace is due to a very large amount of lug setback that leads to the head of the cartridge protruding out of the back of the barrel with enough unsupported brass ahead of the web to risk blowing out the side of the case. A rather uncommon situation. As noted, heasdspace that's due to a deep chamber (like the .308 in a .30-06) will simply lead to case stretching. A Mauser's extractor limits the distance the case head can be from the bolt face. Some play here was designed into the rifle and expected.

Firing cartridges in a chamber with large headspace and then sizing it all the way down to a minimum dimension will overwork the brass, leading to case head separations, which leave a brass cup at the rear of the chamber just like the ones the Germans used to use behind their bag-loaded artillery charges. That's not going to lead to the dire consequences suggested above, but will leave a case remnant stuck in the chamber.

Aside from the above, headspace has to be checked correctly. For a Mauser, the extractor and firing pin with spring should be removed. The Field gauge should be inserted and the bolt very gently closed. A slight extra resistance indicates that the gauge has taken up all of the headspace. A bolt can easily be closed with a bit of extra effort on a gauge that it actually "passes," due to the camming action of the bolt and elasticity of steel. The Go and No-Go gauges are for headspacing new barrels. Headspace is expected to increase a bit in normal service, and the Field gauge indicates an arbitrary value at which the armorers deemed a rifle should be turned in for further inspection and repair.



Z71
Posted - 02/03/2006 : 9:01:59 PM
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OHH my goodness!! Some people operate without a care in the world! I have actualy witnessed a Mauser get wrecked. We did it in vo-tech as a headspace lesson, quite an interesting lesson. And one I have taken to heart. While the experment didn't totaly wreck the rifle(I believe it was a Brno), it did blow the bottom out of the magbox and bulge the box enough to knock chunks of wood off the stock. Also blew the styrofoam block representing the shooters head into chunks! I guess in previous preformances of this lesson, more spectacular results were achieved. What I saw was plenty for me.

A few websites that may(or probably won't!) enlighten the adventurous folks.

http://www.cruffler.com/trivia-October99.html

http://www.forsterproducts.com/pages/gages.htm

http://www.fulton-armory.com/headspace.htm

If some of you fellows don't believe bad things can happen because of excessive headspace, probably nothing I can write to convince you otherwise. But if you do shoot rifles that you know need repair or scrapped, please do it by by yourself! I don't want to be at the range beside you, I don't want anyone I love beside you either. So by all means read the articals above, believe them or not, shoot somewhere that other folks won't be beside you, and if your luck holds you will be fine!

P.S. Hey MCQueenie. I'll sacrifice the rifle if you will shoot it. then we will have some documented evidence. I remember how the vo-tech instructor did it, and it don't take much!



Hitzy
Posted - 02/03/2006 : 10:03:02 PM
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I read that cuffler link up until this part:

Finally, a word on military surplus ammunition. Governments are not charitable organizations. They do not give away, at bargain prices, ammunition for which they have a use. Military ammunition is surplused because it is old and unreliable, it is unsafe, or, in the best case scenario, because the nation in question has moved on to a new family of weapons using a different cartridge (e.g. from the 7.62mm NATO to the 5.56mm NATO). Consequently, shooters should be wary when using military surplus ammunition.


MCQueenie
Posted - 02/03/2006 : 11:43:19 PM
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The cruffler site is a major source of the misinformation floating around the WWW regarding excessive headspace. Its so full of incorrect assumptions and conjecture its not worth taking the time to refute it piece by piece. Forster is in the business of selling gauges so what do you expect? Besides by their second sentence they don't even know what headspace is. Fulton Armory is also assuming the worst.
Z71...why don't you describe the experiment in detail. I'm curious just what "it don't take much" is in terms of actual measurements.



8mm
Posted - 02/04/2006 : 12:08:18 AM
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I have Lee enfield, that was seperating cases, the case would split at the head and a puff of gas, smoke come out around bolt head, no real problems, I wonder what is supposed to be blocking the barrel so airtight to cause a major explosion back by a guys face ?...Also have a mauser bad headspace, just sets the primer out a tad.
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The MOTHER of all reloading Log books.
http://www.cafepress.com/americanproduct


Z71
Posted - 02/04/2006 : 12:44:19 AM
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Not sure why MCQueenie would be interested in terms of actual measurements. Ain't too concerned with excessive headspace. I'm not going to describe the experment because it could be dangerous, and it would be a waste of words, and these written words are wasted as well. I apologize for suggesting anything that may have offended anyone. You guys have won. If MCQueenie wants to know about the gunsmith class project he may email me, and I will gladly fill him in. Then if he wants, he may post it.

You guys got me convinced. Headspace don't mean squat!



MCQueenie
Posted - 02/04/2006 : 01:00:35 AM
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I doubt anyone is offended...other than you, it seems. I was just curious as to how far you have to go to arrive at the conditions to get the results you describe and whether its possible to arrive there under normal real-life circumstances. Surely you can say what the headspace dimension was that caused the blow up. You don't have to necessarily take us through it step by step if you are apprehensive about divulging such information.



GewehrmannII
Posted - 02/04/2006 : 01:05:42 AM
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I'm far from an "expert", bit from reading the above posts, it sounds like everybody has lumped headspace, blown primers, and split cases all into one thing. Headspace is more of a function and accuracy issue, unless the bolt lugs are actually loose in the recesses when the bolt is closed. Then you're talking about set-back, and if it's bad enough, it can break the bolt lugs off and send the bolt body into your eye socket. This never happened to me, but I'd bet it stings! If the bolt on your rifle rattles when it's closed, you've got a problem! Flame on, "experts"!



MCQueenie
Posted - 02/04/2006 : 01:11:52 AM
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8mm...The rear portion of the broken case was acting as a seal. If you get an unrestricted, direct path for the gas to escape backward, it be will forcefull and it will likely cause some damage to the rifle and or shooter. However, it think that scenario is extremely rare where just a head separation occurs. Blown primers and cracked heads due to high pressures and brittle brass are causes as is an out of battery fireing. I suppose it could happen with a head separation in an area where the case is unsupported. I would think that would have to be a gross case of excessive headspace though. That is why I wanted Z71 to provide a little data to shed some light on exactly what was happening in his experiment.



jjk308
Posted - 02/04/2006 : 08:03:35 AM
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Originally posted by 8mm
I have Lee enfield, that was separating cases, the case would split at the head and a puff of gas, smoke come out around bolt head, no real problems, I wonder what is supposed to be blocking the barrel so airtight to cause a major explosion back by a guys face ?...Also have a mauser bad headspace, just sets the primer out a tad.
Precisely what happened on all my Lee Enfields when the brass got too thin from reloading too many times. And in one that had the wrong bolt head. I suspect that the rim and base made a pretty decent seal.

So the moral of the story is, if you have Headspaceophobia you'd better collect nothing but Lee Enfields!

As for the rest of the horror stories in the real world I've never seen a major blow-up that wasn't related to very suspicious reloads.



BigBill
Posted - 02/04/2006 : 11:04:44 AM
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When i built cnc machines with twin cutting heads I noticed the program was going to crash the heads into each other so i stopped it and got my boss at the time. After i showed him the facts He said let it go and sure enough it crashed a brand new machine on a test run broken. HA HA because he didn't listen. My point i don't take chances if it doesn't pass the field headspace test then i don't shoot it. I have a 308 french mas that won't pass the field gauge with .020" shim on it so what you are saying its ok to shoot? Hey i'll get my old boss to shoot it he's a gambling man for sure.



Hitzy
Posted - 02/04/2006 : 2:33:10 PM
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Originally posted by BigBill

When i built cnc machines with twin cutting heads I noticed the program was going to crash the heads into each other so i stopped it and got my boss at the time. After i showed him the facts He said let it go and sure enough it crashed a brand new machine on a test run broken. HA HA because he didn't listen. My point i don't take chances if it doesn't pass the field headspace test then i don't shoot it. I have a .308 french mas that won't pass the field gauge with .020" shim on it so what you are saying its ok to shoot? Hey i'll get my old boss to shoot it he's a gambling man for sure.
If it's one of those MAS 36 converted to 7.62x51 that Century was selling I wouldn't fire it even if the headspace was good.
It's not that the action isn't strong enough, the french made some nice sniper rifles using that action. It's just that the job was so sloppily done that they truly are unsafe to fire. The ones I have seen have simply had the barrel set back to headspace the NATO round. I'm sure you are aware that the diameter of the 7.5 cartridge is larger then the NATO one......far too much case expansion for my liking.
If you have an original one, they are easy to load for running 6.5x55 brass into the 7.5 die.



BigBill
Posted - 02/04/2006 : 6:26:05 PM
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Yup its a century built french MAS 36 ufixem i bought. It appears to have a brand new barrel but the headspace is way off. I wonder if they make a 7,5x54 chamber reamer so i can change it back to the orginal round?



Hitzy
Posted - 02/04/2006 : 6:46:07 PM
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Originally posted by BigBill
Yup its a century built french MAS 36 ufixem i bought. It appears to have a brand new barrel but the headspace is way off. I wonder if they make a 7,5x54 chamber reamer so i can change it back to the orginal round?
If not, 7.5x55 swiss would be nice. I use .284 winchester brass to form it, just run it in the die and that's it. Your MAS would already have the proper bolt face for the .284 case. If you wanted to shoot GP11 it would need to be opened up. The 7.5x55 (and K31) have crept their way into the favorite cartridge spot....

GP11 on the left, my loads with .284 brass neck sized on the right:

http://i4.photobucket.com/albums/y145/BRENDA99/sideview.jpg



keithreid
Posted - 02/04/2006 : 10:56:11 PM
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these arguments are always amusing! oh my god! it closed on a no go gauge, we're all gonna die!!!!
almost as amusing is the "i've seen it somewhere" stories. i see we have another one that the storyteller can't or won't document.

the only rifle i've seen catastrophically disentegrate was an m1 garand that was firing winchester commercial ammo. it had an out of battery detonation from the soft primers.

i have heard lots of fairy tales that started out " i heard".

while i don't shoot rifles with excessive headspace, it isn't because of safety issues. they just don't shoot worth a crap.

my 2 cents, for whatever it's worth. y'all live your fairy tale, i'll live mine.

have a good day! Keith A. Reid



Andy_P
Posted - 02/07/2006 : 08:26:08 AM
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I'm with the "keithreid"s, "Hitzy"s and the likes on this one. The "danger" of excessive headspace is a myth that will not die. There is no point in demanding first-hand (or even tenth-hand for that matter) proof of a gun that exploded due to headspace, because it does not exist. 98%+ of "blown-up guns" are the result of a barrel obstruction, which can have many root causes. Most of the remaining 2% or so are from brass fatigue, faulty firearms and the likes. People will simply cling to their beliefs and no amount of facts will change that. But don't listen to me - I shoot Carcanos and Krags!



MCQueenie
Posted - 02/07/2006 : 5:27:06 PM
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I shoot 'em all and the only headspace gauges I own are in .308Win. for building FALs. I suspect there is good reason we are not getting any actual numbers on the "experiment". BTW...I have no intentions of contacting Mr. Z71. He brought it here as "proof". Let him back his own story up.



Hitzy
Posted - 02/07/2006 : 6:53:07 PM
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Originally posted by GewehrmannII

I'm far from an "expert", bit from reading the above posts, it sounds like everybody has lumped headspace, blown primers, and split cases all into one thing. Headspace is more of a function and accuracy issue, unless the bolt lugs are actually loose in the recesses when the bolt is closed. Then you're talking about set-back, and if it's bad enough, it can break the bolt lugs off and send the bolt body into your eye socket. This never happened to me, but I'd bet it stings! If the bolt on your rifle rattles when it's closed, you've got a problem! Flame on, "experts"!
My thinking on the "loose in the lugs" theory is that when you close the action the sear catches on the firing pin to "****" it, this causes rear-ward tension on the bolt from the stacked firing pin spring, pushing the bolt lugs against the receiver recess. This would prevent any hammering on the receiver, even if there is a few thou setback.
I may be way off on this too though.......



Z71
Posted - 02/07/2006 : 9:41:36 PM
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Hey MCQueenie. I did use the term experment, but it was actually more a demonstration put on by our vo-tech gunsmithing instructor. Not my deal at all, I was an interested observer (from a distance). The deal was set up to demonstrate the dangers of shooting an improperly breeched up/headspaced rifle. I never claimed it "destroyed" the rifle. Definately damaged the magbox/triggerguard though. You fellas may do as you please. I prefer to heed the published warnings, and the verbal tirades of my instructor, and his demonstation. All the safty warnings in the world will not prevent bad things from happening. Usually because the warnings are unheeded.




MCQueenie
Posted - 02/08/2006 : 11:32:09 AM
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Z71, Seems your instructor created a condition where a lot of gas got past the case head. This normally doesn't happen during your garden variety case separation. AFAIAC for your demonstration to carry any weight it has to have some data to go with it. Just what is improperly breeched and headspaced? CREATING a condition to demonstrate an intended result isn't a valid argument if those conditions fall outside reasonable parameters. I could probably take a bolt and grind the face down enough to get the desired results but that simply doesn't apply to real life. Without knowing at least some of the particulars, your instructor's display is meaningless. As far as published warnings... just because its on some website doesn't make it accurate. The Cruffler BS is a prime example.



Max2Cam
Posted - 02/08/2006 : 1:57:12 PM
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Interesting old article about "blowing up" modern bolt-action rifles.

http://www.atthecreation.com/fantasy/blowup/yr.gun.html
 
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