bolt gap/headspace

[drine]

I'm rebarreling my CETME. Barrel is out, cocking handle and support are out and I was checking the fit of the bolt and trunnion. Anyway, in this configuration will there be any boltgap?
I had accuracy issues and a bad barrel. While I've got it torn down, I'm going to check the cocking handle support clearance with the bolt carrier(that is after the barrel is in)

[M1 Tanker]

You can't check bolt gap without the barrel in. The depth of the barrel will set your bolt gap.

[vista461]

In a similar vein I am building my CETME from a parts kit with the SS receiver, I was thinking about mounting my new barrel in the trunion and trying out the pin location that's there already and mounting the trunion in the receiver without welding it yet just to see if that position with give me good bolt gap. Would that work?

[cimmaronkid]

Might, but why do double work? Press the barrel until you get the correct bolt gap and then drill the hole for the trunion pin. Check your rollers and make sure they are not oversize. The way you are wanting to do it, if the bolt gap doesn't come out right, then you have to knock the pin out and rotate the barrel 180 degrees and re-press until the right bolt gap is obtained and then drill another hole for the trunion pin. Once you have the right bolt gap, it is easy to set up the cocking tube for the correct gap and then you won't have any problems in those areas.

[drine]

That's what I was hoping otherwise more work.

[vista461]

Might, but why do double work? Press the barrel until you get the correct bolt gap and then drill the hole for the trunion pin. Check your rollers and make sure they are not oversize. The way you are wanting to do it, if the bolt gap doesn't come out right, then you have to knock the pin out and rotate the barrel 180 degrees and re-press until the right bolt gap is obtained and then drill another hole for the trunion pin. Once you have the right bolt gap, it is easy to set up the cocking tube for the correct gap and then you won't have any problems in those areas.

Yeah you're right, thought I might get lucky, but the way mine's been running lately, I don't have a chance:D
Thanks

[grifter95]

My bolt has some gap when it is locked into the trunnion, but before the barrel was installed! Is this a problem. This is an unground parts kit bolt?

[cimmaronkid]

Easy way to tell is to measure the bolt. Should be 1.835". Since it is a kit and NOT a CAI build I doubt that the bolt is ground, but measure anyway.

[grifter95]

So if my bolt has a gap when locked into the trunnion and no barrel....is this a problem?

[M1 Tanker]

There is nothing to measure if the barrel isn't installed.

[jfowl31]

but tanker, if the trunnion is too narrow where the rollers press out, could this not also give some sort of false bolt gap? I woulda thought that without the barrel, there would just be no bolt gap no matter what.

[grifter95]

When I "close" the bolt, even not inside of the trunnion, a bolt gap exists? Is this a problem? Or am I misunderstanding something. I have revied the manuals for the procedure for checking and still find a gap exists!

[SSwee]

When I "close" the bolt, even not inside of the trunnion, a bolt gap exists? Is this a problem? Or am I misunderstanding something. I have revied the manuals for the procedure for checking and still find a gap exists!

You've missed it a little. The gap you want to measure is created by the contact between the trunnion to rollers to locking piece that pushes the carrier back off the head. It's hard to explain without a pic and being in person. It is the relation of all these parts together as an assembly. There is a pic somewhere here on the forum of a cut-out view of the assembly that may help you get a picture of everything. I'll try to find it if someone else doesn't post it first.
SS

[jfowl31]

grifter is saying (if I read him right) that even when he pulls the bolt and carrier out, he can "lock" the bolt, and a gap still exists. don't sound right to me, but I dont have mine right here in front of me.

[Seattlefungus]

These are the HK version of the roller system. Without the rollers reaching the limit of the trunion recess, no accurate gap can possiblly be obtained.

[SSwee]

grifter95,
As to your original questions.
The bolt gap on an uninstalled carrier is normal, even with the head locked back. There is no problem there. The only concern with bolt gap is when it is out of specification when checked with the proper procedure.
SS