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Head Space Brain Work |
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03manV
On Point Joined: Mar 01 2020 Location: near Charlotte Status: Offline Points: 262 |
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Floyd,
we are in total agreement. Military and commercial entities and their gauges are frequently different. I'm sure the "specified" numbers and limits are conservative- the statement that you made when you started this thread!
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Don
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sling00
Hard Corps Joined: Apr 21 2016 Location: Tennessee Status: Offline Points: 941 |
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Prime example is .303 British Enfield. A SAAMI specs field gauge is .070 whereas the British mil spec field gauge is .074.
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1996 |
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I think it's a safe bet to assume there are many carbines out there shooting past 1.302, well past that. All the field gauge indicates is that head-space is longer than the gauge, it doesn't indicate how long it is and how long it's been shooting that way....unless it is accurately measured. I've looked at guns for owners in which a field gauge would practically rattle in the chamber and I am pretty sure they just keep shooting them. Like an ME gauge...it's a good indication of use, but doesn't necessarily condemn the carbine. These carbines were made to shoot rather lose with torso-shot accuracy to overcome action-pollution of mud, sand, salt-water, blood and guts. Ruptured cases due to sloppy head-space in a carbine have to be rare, if at all existent. Of course, one can blow-up any gun if he tries hard enough I suppose. These things were proofed at 140%. A tight muzzle and a 1.295 head-space might indicate a little fired gun, but I would gladly discount the right used carbine with an ME of 3 and head-space of 1.304 by $500-$600 and take it off your hands any day. Not for a range gun that is often fired, but for one to occasionally shoot, or that "closet gun".
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Sawbones
On Point Joined: Mar 04 2022 Location: Texas Status: Offline Points: 150 |
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Very interesting and informative thread. After careful scrutiny of all the opinions and facts presented I agree 100% w/ everything FloydtheCat has stated, particularly his last reply. Toss any cases fired 3 times otherwise risk splitting/disintegrating brass Ejector not locking? First, check the springs in the bolt. (see CMP Forum: M1 Carbine section, "Fail to chamber question", page 3, last reply 3-5-22
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"I think youngsters need to start thinking about what kind of world they will leave for me and Keith Richards". Willie Nelson
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JRBrid
Recruit Joined: Feb 02 2016 Location: Friendswood, TX Status: Offline Points: 52 |
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Personal Experience with a Carbine that Was Out of Headspace
I’ve been hesitant to jump into this discussion,
as I don’t feel it is my place to tell others what they can or should do with
their guns, but I have decided to go ahead and share this personal experience
with a carbine that was out of headspace.
Hope this helps … here is the story: A few years ago, my best friend and I were enjoying a day at the range shooting carbines. We had several with us, including one that he had recently purchased at a local gun show. We were having problems with the new gun, several failures to fire. Examination of the rounds showed light firing pin strikes, but the problem was not consistent and we were thinking that maybe the bolt needed a good cleaning. We continued shooting, when suddenly my buddy, yelled, dropped the new carbine, and backed away from the shooting bench. I’ll let him tell you what happened in his own words: “There was a flash in front of
my face and something hit me. I dropped the gun and stepped back from the
bench. The case had separated. The stock was split. The
magazine case was bulged and the base, along with the follower, spring and
remaining rounds were blown out. The extractor, firing pin, ejector and
spring were missing from the bolt. We found most of the pieces of
the magazine, bolt and brass. There was something embedded in my forehead about 1”
above my glasses. There was no sign of infection so I waited until the
swelling went down and finally pulled a BB sized piece of casing brass out of
my forehead.” Obviously, this was a traumatic
end to a day at the range – we were just thankful that it wasn’t much, much
worse. Using some thin washers and head
space gauges, we estimated the gun in question was as much as 0.030” out of
headspace. After this experience, we very
carefully checked the headspace on all of our carbines, and corrected any of
them that showed excessive headspace with a field gage. Fortunately, we were able to correct most of
the issues we found by swapping bolts, but the one did require a new
barrel. Bottom
line, for us at least, is that life is too short and precious to take the risk
of shooting a carbine that has excessive head space. We still have the pieces of brass
and the stock. If anyone would like pictures,
just PM me. Again, hope this helps. Respectively, Jim |
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Jim B.
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1996 |
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Spec’s give you 22 (1.302-1.280). My experience has been they start becoming problematic much past 1.310, which would be 8 out of spec. I would think the gun would stop firing at all. Other things could be at work. The only rupture I have ever read about was eventually blamed on faulty ammo (thin brass).
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Smokpole
Hard Corps Joined: Oct 21 2019 Location: Madison ohio Status: Offline Points: 1052 |
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JRBrid, that sounds more like an out of battery explosion than a head space issue. Was that carbine by any chance a commercial carbine? Or more specifically a Universal? Universal took some shortcuts in their manufacture that allowed their carbines to fire out of battery and what you describe is classic out of battery firing.
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03manV
On Point Joined: Mar 01 2020 Location: near Charlotte Status: Offline Points: 262 |
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Please tell us about the ammunition.
I'm with Smokepole about an OOB firing, but a case head separation would do it too.
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Don
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David Milisock
On Point Joined: Aug 03 2019 Location: USA Status: Offline Points: 334 |
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I tend to lean toward an out of battery firing also.
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David Milisock
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JRBrid
Recruit Joined: Feb 02 2016 Location: Friendswood, TX Status: Offline Points: 52 |
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It was not a commercial carbine - actually a Winchester with mostly Winchester parts, including a nice Winchester stock that was split. We considered OOB, but found couldn't find any evidence on the bolt lugs or receiver to support that. This is the gun we replaced the barrel on, and have had no trouble with it since doing that - same bolt, same springs, etc. The one thing we could prove was that the gun was badly out of headspace, on the order of .030 inches beyond a Forster field gage. I will leave you to draw your own conclusions ....
Jim
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Jim B.
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1996 |
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Wow…30 past a 1.30 field gauge! I can’t see how that could not be noticed before it was fired. Not bashing anybody here….we just like to try and figure out what happened in cases like this.
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Sawbones
On Point Joined: Mar 04 2022 Location: Texas Status: Offline Points: 150 |
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Faulty ammo must be considered. Was the ammo used reloaded stuff? Must consider case separation due to metal fatigue. Case reloaded too many times renders case thin and brittle. That in conjunction with a way too long headspace and you've got the perfect ingredients for disaster. I refer all to Lyman Reloading Handbook, 49th edition , page 48. A new un-fired case will not disintegrate when fired unless other factors are present such as using too much powder, wrong powder, excessive crimping.
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"I think youngsters need to start thinking about what kind of world they will leave for me and Keith Richards". Willie Nelson
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Rebel92
Grunt Joined: Jul 20 2021 Location: Hattiesburg, MS Status: Offline Points: 541 |
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So was the headspace on this carbine 1.36? That would swallow a field gauge right?
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JRBrid
Recruit Joined: Feb 02 2016 Location: Friendswood, TX Status: Offline Points: 52 |
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Sorry, this happened some time ago, and we no longer remember the details on the ammo being used -- not sure if it was new commercial, surplus GI or reloads.
Jim
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Jim B.
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03manV
On Point Joined: Mar 01 2020 Location: near Charlotte Status: Offline Points: 262 |
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I'm sorry but without knowing the ammo involved and not measuring the headspace before the accident, one just cannot draw a firm conclusion as to the cause.
The "cause" of the accident as you state was a case separation; what caused the case separation cannot be discerned from the information given. It is good your buddy wasn't more seriously injured. The real lesson here is to check any firearm before firing and when firing a "new, used" firearm for the first time use known "good" ammo. When encountering an unexpected series of malfunctions it is best to stop and determine the cause.
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Don
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1996 |
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I don’t see how it would have fired at all under normal circumstances with the bolt closed and rotated on a chambered round. My experience is they stop shooting when it gets much past 10-12 thousandths longer than a field gauge. 30 thousandths longer than a 1.300 gauge would be 1.330.
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JRBrid
Recruit Joined: Feb 02 2016 Location: Friendswood, TX Status: Offline Points: 52 |
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We have used ammo from that same box/lot in other carbines both the day of the incident and since, and have had no other problems. The only difference we have been able to identify is that the one carbine that we had the incident with was badly out of headspace, and all of the others gaged as good, again with all determinations being made with a Forster field headspace gage.
Jim
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Jim B.
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Smokpole
Hard Corps Joined: Oct 21 2019 Location: Madison ohio Status: Offline Points: 1052 |
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Was part of the case stuck in the chamber? Or was the case simply split?
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JRBrid
Recruit Joined: Feb 02 2016 Location: Friendswood, TX Status: Offline Points: 52 |
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Yes, part of the case was stuck in the chamber. The case completely separated just ahead of the base of the round.
Jim
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Jim B.
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1996 |
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Can we call this a case head separation as opposed to a rupture?
The only time I have been able to find anything about a carbine case rupture was an individual who took his carbine to a gunsmith after he had one blow-up. Gunsmith determined it was a case head separation, because the owners ammo blew-up in his test gun as well…..bad ammo. I have been present or experienced two ruptures and one case head separation in my life. All were from semi-auto 9mm pistols with unsupported chambers. The separation left most of the brass in the chamber.
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