After having a bolt failure in my old IBM M1 that destroyed the receiver. I have a question for my re-build. Which will be a Fulton receiver, barrel, and headspaced bolt.
Should I have a 'Field' (1.250") gauge on hand to check the headspace occasionally? I'm just kind-a paranoid for the future failures.
Oh, I'll use my original barrel to mate with a good USGI receiver and have pared with a matched bolt. I'll pack away this for the future. I'll use the Fulton set-up for range 'plunking'.
I guess my question is; How often should the headspace be checked in a well maintained gun?. Or is checking necessary?
I have had my 1942 Inland since 1986 and I have put at least 20,000 rounds though it in the preceding decades (and that's a conservative number). In that time I did manage to break an extractor, but that's it. Everything else about the rifle is essentially perfect. My carbine has been amazingly reliable over all those years...and was mostly reliable even when I broke the extractor. When that happened, the extractor broke at the post, so it was completely gone...yet, the rifle still functioned normally for 14 out of 15 rounds in the magazine. I have to say, that impressed the hell out of me!
Now on to headspace, bolts, and broken bolts.
I have encountered a broken M1 or two over the years. i worked for one of the major surplus small arms companies in the '80's, and we imported 7,000 M1's from China (WWII leftovers), and 4,000 M1's from Israel. This was around 1985-ish. I was the lucky guy who got to go through all 11k Carbines. So I've seen a decent number of broken carbines.
I have never run into an M1 Carbine that was so worn and stretched that the headspace was excessive. I have always been of the opinion, if an M1 Carbine's headspace is excessive, the issue is parts or receiver that are out of spec from the factory. Meaning, they were guns that managed to leak through and make it out into the field rather than having the headspace issue corrected.
So with that in mind, it's never a bad idea to check headspace on an old surplus gun when you get it. US Carbines saw at least 2 major upgrade/re-furbish programs where all the Carbines would be taken to the depot, inspected and anything found was corrected. They often re-Parkerized the rifles at that point as well.
When these upgrades were done, there was no effort to keep all the parts together. They were just thrown into a bin, and fished out to build the guns back up when the finish work was done. So its conceivable that a carbine could be assembled with a bolt that was a bit out of spec, and that could turn out to be a bad thing.
So typically, the rifle was either out of spec for headspace from day one, or it got that way during an upgrades/arsenal refurbish.
On my Carbine, a field gauge was dropped on on day one, and all was good. Here we are 30+ years, and 20k+ rounds later and headspace on my rifle is unchanged.
So all this is to say...if you're really worried about it, drop a field gauge in every 2-5k rounds if that will make you feel better.
Of course I'm talking GI guns...you're talking about using a Fulton receiver. Maybe receiver stretch is something to worry about with a commercial receiver (I have ZERO experience with Fulton's carbines or receivers). But what you described, I have never see happen with an M1 Carbine.
I will say, there is a reason commercial M1 Carbines were so hit & miss. An M1 Carbine is not an easy rifle to manufacture at all. Many are unaware that the Carbine was actually more expensive to produce than the Garand. Not by much, but more expensive nonetheless.
Now bolts do break at the locking lugs. Most often it's the right side lug, because the extractor's over there and does weaken the area a little; but I have seen broken left lugs as well.