New Bolt and Headspace

[Rustship]

Just curious, since all parts are mil-spec, how many of you guys have bought new bolt and found that the headspace changed. Is this something to absolutely, postively check? or can you slap any bolt in and go. I'm sure this is something the military thought of in developement. Is there a lot of variations between all of the makers bolts? Just something that came across my tired old mind today,

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[45B20]

Rustship

I have checked a lot of Carbine’s (M1&2) headspace and changed a number of barrels, mostly taken off other Carbines but a few were new barrels, I found the variations in headspace varied more with the Carbine than with the M1 Rifle. However I found very few Carbines that would not pass the headspace test (not close on the 1.302” Gage) with switching bolts. I was always lucky in having a good number of spare bolts, a lot new. Even when a Field Test Bolt closed on the 1.302”, I could almost always find a bolt that would not close on the 1.302” gauge. These were ARVN’s Carbines, different set of rules. And no,, I did not note which manufacturers fit best or try to match manufacturer to manufacture. At the time (1967 to 1968) I was only vaguely aware of what the different marks meant.

Pre 1969 there was a requirement that all re-barreled Carbines must not close on the 1.295” Gage and no Carbine that closed on the 1.298” Gage could be returned to stock, it had to be ‘evacuated’ (sent) to a Depot or a Fifth Echelon Rebuild Facility. Some time after TM 9-1276, Feb 53, was issued (released) these requirement were changed. I do not have these Changes, but I remember them and the only headspace requirement was that the bolt not close on the 1.302” at any level of Maintenance. TM 9-1005-210-35, dated June 69 only list one Headspace Gage, the 1.302”.

I guess the 1.290” would be the same as a GO and the 1.302” a FIELD REJECT but I only remember referring to them by their size.

45B20

[Rustship]

Thankd 45B20, Now that you bring up that 1.302 measurement, I have seen field guages that have that measurement which is different than the No-Go, and Go guage. So I guess there is some forgiving thousands there. I would guess the 1.302 is the extreme, for wartime (shoot it until this dont work) measurement). I would think back in the day, a solder whould go to the company gunsmith if he had broken a part such as an extractor, and say give me a new bolt, put it in and go back to the line.

[45B20]

Rustship

The headspace specifications have changed over the years. To call a 1.302” Gage a “extreme for war time” would be incorrect. It was simply the gage that determents if a Carbine is serviceable or not, at that period of time. In 1947 closing on a 1.300” Gage would make it unserviceable, in 1954 closing on a 1.302”Gage would make a Carbine unserviceable. The TM in force at the time, determined what the specs for any particular Small Arm was. Ordnance changed specifications as they gained experience and data on a weapon. There were no ‘War Time’ head space specs on any US Small Arms.

There was really no company gunsmith, there was a Company Armorer,, who was not trained or authorized to order and/or change bolts and he had no Headspace Gages. Not saying he could not acquire the odd bolt or two, but it would be very difficult for him to have Headspace Gages. And I see no reason why he should. During combat there is regrettably extra weapons laying around, especially at an Aid Station. If a weapon does fail, the Company Supply Room/tent (of which the Armorer is part) has a float of extra Individual Weapons which would be issued to replace the faulty weapon. The Armorer could repair some problems, but if the fault was beyond his authorization to repair, he would then sent the faulty weapon to the Direct Support (3rd echelon) unit supporting him or call for their Contact Team to come to his location.

During a war, the Company Armorer in a very busy individual, he has a lot of supply reasonabilities, he does not need any more to do.

45B20

[Rustship]

Thanks 45B20,

You guys are smart, keeps me from having to look stuff up. I appreciate the info, because a gunsmith I am not.

[hammonje]

Found a few that would close on a field gauge. Winchester bolt looked like new with 95% green park and the barrel gauged TE=2.0. The original Inland round bolt would not close on the no-go gauge and closed on the go gauge. That's why you check the headspace. You cannot just swap bolts. Better to spend the $75 on a set of gauges. They are nice to have when buying a carbine FTF since you can make sure it headspaces correctly and is not some mixmaster of junk parts someone put together.

[ulflyer]

Rustship: I dont' claim to very knowledgable about this subject, but in the last two years, out of 20 CMP carbines that I have done some "restoring" on and changed bolts, only two did not guage right, using a field guage. In each case, by swapping bolts, I found a fit for each bolt. Both of the guns and bolts were Inland, but probably only because thats the make I have the most of.