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chas442
March 20, 2015, 12:32
I have 2 CETME riles made by CIA and both are marked 308. I have a set of headspace gauges ranging from 1.630 to 1.640 in .001 increments. My question is, is it possible to determine, using headspace gauges, if the chamber is short like a 308 chamber or longer like a 7.62x51 chamber.
I currently have milsurp ammo.
I am aware that headspace is something that cannot be easily changed on the CETMEs.
I would like to know if commercial ammo might cause me some concern.
I have already corrected a number of FAL type weapons to be within 308 specs to eliminate ammo issues.

SAFN49
March 20, 2015, 14:43
Use 7.62x51 brass cased mil surp only.

12v71
March 20, 2015, 20:23
Huh? My CETME loves commercial .308. No issues so far, is it going to kaboom on me? :confused: Other than the fluting, the brass looks fine around the base.

SAFN49
March 20, 2015, 20:37
Huh? My CETME loves commercial .308. No issues so far, is it going to kaboom on me? :confused: Other than the fluting, the brass looks fine around the base.

Wait till you get a round stuck in the chamber. Commercial brass is thinner than mil surp. It can actually swell and fill the flutes. Then you have to beat it out with a cleaning rod. :biggrin:

12v71
March 20, 2015, 21:11
I really haven't seen the commercial brass pressed that deeply into the flutes. I've heard that before, but I'm not seeing it with the PMC that I normally use. The flutes don't show much deeper than a line on the brass.

chas442
March 21, 2015, 12:40
I am glad to hear see that some of you are having good luck with 308 ammo. Is it safe to assume that your CETMEs are CIA built?
Just curious if any of one of you have CETMEs in my serial # range?
One is C465XX the other is C351XX.

BIG50
March 21, 2015, 16:24
You do not ues headspace gauges on the roller lock cetme or HK you check headspace measuring the bolt gap this is the space between the bolt and carrier when locked up in battery. I would not ues commercial ammo in that gun like mentioned above. Surplus 7.62x51 casses are annealed much stronger. You have been lucky so far but you will have one blow up on you one day aske me how I know been there done that. I have built thousands of HK and cetme roller lock guns I know them very well.

12v71
March 21, 2015, 18:38
I am glad to hear see that some of you are having good luck with 308 ammo. Is it safe to assume that your CETMEs are CIA built?
Just curious if any of one of you have CETMEs in my serial # range?
One is C465XX the other is C351XX.

C620XX here. Got it from another Files member. Not sure if he had any issues ironed out of it. It's worked well for me.

ftierson
March 21, 2015, 18:46
Wait till you get a round stuck in the chamber. Commercial brass is thinner than mil surp. It can actually swell and fill the flutes. Then you have to beat it out with a cleaning rod. :biggrin:

Commercial brass might be slightly thinner (I'm thinking especially Win here), but it generally is harder...

I've been shooting both military 7.62x51mm and commercial .308 Win. in an HK-91 and a couple of CIA CETME rifles for decades without problems. Some of the softer brass (like Venezuelan CAVIM) is formed more to the flutes than harder stuff (like Winchester commercial ammo) which usually is mostly discolored by the flutes and not 'shaped' as much...

My point is only that the military brass (which tends to be softer) is 'deformed' more than commercial stuff...

Forrest

gunplumber
March 21, 2015, 20:00
It doesn't make a damn bit of difference. For all practical purposes, all commercial .308 and 7.62 are dimensionally interchangeable in the HK. For functional purposes, a bullet in the 150 grain range at 2750 fps is "NATO SPEC" and will function best.

Bolt gap from 0.1 to 0.5mm, with closer to 0.5 being ideal.

chas442
March 21, 2015, 20:20
GP Haven't installed the +8 rollers yet. Will install on Monday and check Bolt gap and then address Cocking tube gap. I just wanted to know if its possible to check actual headspace to determine if it within 308 specs or if its long like 7.62x51

SAFN49
March 22, 2015, 01:09
It doesn't make a damn bit of difference. For all practical purposes, all commercial .308 and 7.62 are dimensionally interchangeable in the HK. For functional purposes, a bullet in the 150 grain range at 2750 fps is "NATO SPEC" and will function best.

Bolt gap from 0.1 to 0.5mm, with closer to 0.5 being ideal.

That would be wrong. Ideal, according to the HK manual, would be closer to 0.012", not 0.020".

chas442
March 22, 2015, 12:07
You are mixing metric with inch. Same gap.

chas442
March 22, 2015, 12:26
My OP was more a matter of curiosity than necessity. I have about 6K of "reworked" indian ammo. I know its the crap stuff. I had a squib in an CIA R1A1. Fortunately the bullet lodged in the barrel only far enough to prevent another round from chambering.
Seeing that I had substantial amount of ammo I was afraid to use,I pulled them all down. I put the extruded powder in one container(s) and the ball powder in another container(s). I then reloaded all cases that looked good and dumped the rest.
During the teardown I checked powder charges in the first 100 cases. It ranged from 37.0 gr to 47.0 gr. Not to mention the cases that had no powder at all. I even found what looked like a piece of brass broken from the neck of a cartridge inside one case.
I downloaded all rounds to 40.0 gr so I could use it for plinking.
The accuracy in the R1A1 with this ammo went from 12+ inch groups to 3 to 4 inch groups.
As a side note I also weighed the empty cases on a large group during the teardown and found that the weight of the empty cases was very consistant.
I may try reloading some in the future. No need at this point.

gunplumber
March 22, 2015, 13:00
That would be wrong. Ideal, according to the HK manual, would be closer to 0.012", not 0.020".

(sigh)

0.1mm = .004"
0.5mm = .020"

With use, the gap gets smaller, so setting the gap on the max end gives the longest service life.

Also, there is setback on initial firing, closing the gap slightly.