Semi-auto headspace question.

[BamBam-31]

I recently purchased an Egyptian FN-49 in 8mm. I had my local smith check the headspace, and he informed me that my bolt closed on a no-go gauge. He then added two layers of tape to the no-go, and my bolt wouldn't close on that.

He explained that, although my bolt closed on the no-go, the rifle was still okay to shoot because milsurp semi-autos are purposely made with sloppier headspacing to compensate for dirt that might get into the works during battle. The taped no-go gauge was simulating a "field" gauge (never heard of one), which would be the true no-go for a milsurp semi-auto.

Does this sound about right?

 

[BryanP]

Here - Instructions for headspace gages.

If a real field gage passes then the rifle MAY be safe to fire. I don't know that I'd trust a "simulated" field gage. I'd rather just choose not to fire a rifle than have it go boom in a bad way right next to my face.

 

[Big_R]

Headspace is a tricky thing. If the action is solid (no lugs in the process of setting back, etc.) it's probably OK to shoot. If you handload, only neck size or your cases will most likely seperate after a couple loadings. I wouldn't have any problem shooting standard pressure ammo in it.

Ryan

 

[Jim K]

GO and NO-GO gauges are used in manufacture and in replacing barrels/bolts. For a used rifle, the field gauge is a valid check on headspace. But simulated field gauges can be iffy, even though I have done just what your gunsmith did. If the "tape" was something like Scotch transparent tape, the test should be OK, but look at fired cases for any signs of stretching. If it was something thicker (duct tape), I would want a test with a real field gauge, even if I had to buy it myself.

Jim

 

[BamBam-31]

Thanks for the link and info, guys.

My smith used what looked to be masking tape, which is somewhere between Scotch and duct tape, I'd think.

He also said to look for bulging or stretching in fired cases, but only just to be safe. He sounded pretty confident that it was safe to fire.

Also, the barrel was somewhat canted when I bought it, so I had my smith tighten it a bit to square it up with the receiver. That'd tighten up the headspace an iota, too, wouldn't it?

Maybe I should try Mike Irwin's tire technique for the first shot....

 

[Jim K]

I think you will probably be OK. I don't always check headspace on milsurp rifles before shooting unless the guns fail my "eyeball" check or have something that doesn't seem quite right.

I would do as the gunsmith advises and keep an eye on the cases for signs of stretching. Bulging is a different story and is usually the result of an oversize chamber, a fairly common condition in military semi-autos.

Jim

 

[Mike Irwin]

"Maybe I should try Mike Irwin's tire technique for the first shot...."


Nah, I now suggest huddling over it. That way if there's an action failure, you can see exactly where it happens...