

Posted: 3/10/2005 5:47:38 AM EDT
Good question for Chuck as I see he's back.
I know SAAMI specs and military specs for the 30-06 Garand are different. Is there any established relationship between a Forster gauge and the military gauge? In other words, what are the military headspace dimensions? I see them in the 1.9" range, while Forster gauges are in the 2.0" range. I realize the datum point is different, but it's very confusing. |
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It is my understanding that it is perfectly acceptable to use the Forster gauges. My M1 closes on go, and dosen't close on no-go. Considering the age of the parts I build her with, I was very pleased when this occured.
I should add that I called Forster direct and they verified that is was ok to use thier gauges while headspacing the M1. And Jerry Kuhnhausens M1 shop manual mentions them. |
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I guess I should clarify my question. While I'm certain that using SAAMI gauges put the Garand in the correct headspace range when barreling, I'm also certain that closing on a SAAMI NO-GO does not mean the headspace is excessive. For that matter, closing on a SAAMI FIELD may not mean that the headspace is excessive.
I'm just trying to find the military headspace numbers as they relate to Forster numbers. |
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Well, I have never heard anything about different gages for 30-06 for sammi and USGI. 30-06 is the same as M2 ball, dimentionaly speaking. If you have a rifle that closes on a foster field gage, I sure as hell wouldn't shoot it.
If the rifle closes on a no-go gage but doesn't close on a field gage, the rifle's headspace is starting to get to the point where it is excessive, but still safe to fire. There are differences in 308v7.62 and 223v5.56. There are none that I know of for 30-06. If there are, please provide documentation as I have never heard of that. Hope this helps. |
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.30 Caliber M1 Rifle headspace should be between 1.940" (GO) and 1.950" (Field reject). 1.946" or less is arsenal re-issue standard. 1.950 or less in the field is fine.
Unless you have the military gage you will have to strip the bolt to check it. There are really no safety issues involved here, as long as minimum chamber size is there. General Hatcher used a grinder to induce massively excessive headspace without harm -- accuracy suffered, but that was it. -- Chuck |
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isn't 1.946 field and 1.950 no go?? |
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NO-GO is a factory/arsenal gage designed to allow the maximum service life in the field. Once the rifle is in your hands only the longer FIELD (Reject) gage has any meaning.
In order of length the gages are: GO (minimum chamber length for reliable operation) NO-GO (maximum chamber length for new rifles or rebuilds leaving the factory/arsenal) FIELD (maximum length). The Army actually had over a dozen gages for the M1 Rifle. I've only listed three of them for field service. Match rifles can get picky about their headspace, but that's an accuracy not safety issue. Match M1 Rifle has been an oxymoron for a couple decades, though ![]() You should be able to find commercial ".30-06" gages of these lengths. As noted earlier you'll have to strip the bolt completely to check as the extractor and ejector will get in the way. Use light finger pressure at most witht the bolt. Do not sweat headspace! It's a gunstore commando topic. As long as you're shooting good, military M2 Ball it really doesn't matter. M1 Rifles don't "blow up" from excessive headspace. They may get sloppy accuracy, but that's the limit. Note that M14/M1A gages are largely unavailable. But the M14 GO gage is the same length as the SAAMI bolt gun NO-GO gage. Use the length, not the commercial name. Don't let someone try to sell you a new bolt for your M1A 'cuz it almost closes on a SAAMI Field gage -- it's in spec! -- Chuck |
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Yes and no. This is the reason for my post. The numbers that Chuck posted (1.940", 1.946" and 1.950") come from the various army manuals I've found on the web. The problem is that the military appears to use a different datum point for measuring the chamber. To wit, look at the Forster gauges: www.forsterproducts.com/Pages/gages.htm The measurements given for their 30-06 gauges are 2.049", 2.055" and 2.058". Obviously these gauges are not measuring a chamber that is 0.100" bigger, so I was attempting to get a handle on how these gauges translate to the military chamber measurements. In other words, there is a fixed number I must subtract from the Forster sizes to get to the military sizes. The problem is that the individual Forster gauges do not correspond to the military gauges in function. I don't have a fear of excessive headspace in my case, but I would like to understand the relationship here. |
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![]() Granted the rifle itself won't blow up, but what about the likelyhood of having a casehead separation.THAT is the real problem with excessive headspace. That can cause you to be thankful you wore your shooting glasses and give you hours of fun picking stock splinters from your hands and arms. Tim |
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As mentioned by Chuck, excessive headspace in an M1 allows the bolt to close fully. In that condition, it is almost impossible to blow up, or even damage an M1, using standard ball ammo. Case seperations, again mentioned by Chuck, are of course a distinct possibility.
To give you an idea of how strong the M1 action is, Gen Julian Hatcher, in a scientific series of tests, finally ended up loading an entire cartridge case with proof testing powder (normal amount was a small fraction of the entire case volume}. Long story short, the rifle survived, and was still useable. |
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Try reading comprehension, he made no mention of it - I did. Don't know about you, but I don't want 50,000 psi to suddenly become uncontained inches infront of my face. I guarantee you it will split the stock, whether you'd be injured is another story, but better safe than sorry, and his advice doesn't cut it.
Go back and check again, I believe you'll find that although the action did not catastrophically fail, one of the bolt lugs did crack. 'Course if you believe Chucks' statement about headspace not mattering, you probably think this would still be a servicable "problem". Tim |
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Alot of 7.62 ammo has been accidently fired in 30 Cal M1's with no ill effect other than accuracy. The Extractor will hold the case head against the bolt face, firing M2 ammo in an M1 with excessive headspace will not cause casehead seperations. It will shorten the life of the brass though if you reload and full length resize everytime.
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Only by idiots.
Fixed it for ya, but hey, its your face, go ahead. Tim |
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Regarding 7.62x51 fired in a 30-06 M1, IIRC Franfort Arsenal performed testing of this around the time the M14 was being considered for adoption. Their conclusion was that it was OK to do in an Emergency, using USGI M59 (or M80) ball ammo.
Major Culver has written on his website (jouster.com) about unintentionally firing 7.62 in a .30 cal Garand at the National Matches when both ammunition was issued and he received the wrong one. He suffered no ill effects other than low hits on the target. I would not make a steady habit if firing 7.62 in a 30-06, but would do so without hesitation if the choice was being taken prisoner by some zombie or murderous islamic wacko. |
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Dear Garand06, please allow me to beg your pardon. I am only human, and sometimes make mistakes.
Who's talking uncontained? Isn't the bolt fully closed, and a cartridge of the proper head diameter in the chamber? We're not referring to a cartridge that will interfere with the bolt closing.
Didn't you say above what the rifle won't "blow up"? which is it?
True, the bolt lug cracked, but you left out the rest of the story. Hatcher then fired 5,000 standard rounds through the rifle with the bolt whose lug was cracked with no ill effects. (HNB, Pg 206) Why did you leave that information out? In my experience, replacing the bolt in a Garand is fairly straightforward. Your experience may be different. Regardless, my point was exactly that the action did not catastrophically fail. |
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Interesting you should mention this. I once had the experience of firing some crappy Izzy milsurp through a Modelo 1912 Mauser, made originally by Steyr, in Austria. A couple of the cases failed catastrophically, with a longitudinal seperation beginning at the primer pocket, travelling radially across the case head, and forwards about halfway up the body of the case. The net result was a slight puff of gas in my face. No drama, no explosion, no splinters, no nothing except a story to tell. Point is, that a case failure of that kind, in a well-made rifle is no big deal as long as you are wearing shooting glasses. Perhaps you are personally more familiar with rifles blowing up. If so, please relate your personal experiences. |
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Chuck, thank you for posting this. I've been saying the same thing for years, and maybe people will finally stop using the NO-GO gauge as a test for used military surplus rifles.
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Match shooters may want to keep their chambers between GO and NO-Go for accuracy purposes.
No shooters in the world worry about headspace but us! Bubba Deer Hunter shoots hundreds of rounds a year and hasn't heard the word. Nor has he (or any of us) been harmed by "bad" headspace. Soldiers in Iraq who had their rifles checked last week (with Gage, Headspace, Field) can shoot thousands of rounds in the next 6 months without difficulty, even if their rifle would fail the Field gage this week. Even professional gunsmiths mis-use headspace. A year ago I sent a new M1A receiver and a complete HRA M14 Rifle (less receiver) out west to get the "kit" assembled. I received a phone call that I needed a new bolt (for $50 trade, no less) because my new HRA bolt would partially close on a SAMMI Field gage. "Great!" I responded. That means it's tighter than M14 NO-GO requirements. [Long silence on their end, then] Yeah, you're right. Lots of folks would have bought a replacement bolt for a rifle meeting new specs from the arsensal. I keep waiting for documented, primary source data of M1, M14, or M16 rifles blowing up due to excessive headspace. And I'm sure I'll continue to wait. Should we move to the nonsense differences between 7.62mm NATO and .308 Winchester and we shouldn't fire one in rifles maked for the other? ![]() -- Chuck |
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If the case separated, it is uncontained.
Yes, and I don't consider a case failure that blows out the magazine area of the stock to be the rifle blowing up.
Simple, I had completely forgotten that. (I'm only human, too ![]() Perhaps I am simply paranoid, and therefore incorrect in my position, but I will not fire any weapon that does not check out "normally" and I don't feel that excess headspace is normal. Tim |
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Back to my original question...Does anyone understand the relationship between the sizes listed on Forster gauges and the military headspace measurements?
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Read my post above. There are no differences in 30-06 dimentions between the military and commericial, like in 7.62/5.56, that I'm aware of. |
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Please reread MY posts. As I mentioned, gauges like Forster appear to use a different datum point when measuring the chamber. The gauges may be identical, but they certainly aren't labeled as such. Furthermore, I think we've already established that a military rifle will close on a SAAMI field gauge long before the military gauge says the barrel needs to be replaced. I'm NOT making the claim that there is a difference between commercial 30-06 ammo and military 30-06 ammo. |
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