These are the steps I used to make the Cetme a safe shooter.
The original bolt gap with a ground bolt was .011
The ground bolt length was 1.8265
New bolt length is 1.834 they seem to range from 1.834 to 1.842
This bolt is ground .008
The .008 is ?false gap?created by the grinding.
Subtract that from the measured gap of .011 and the actual gap is .003
The spec bolt gap is .004 min to .020 max.
I remote fired this one for experimental purposes only.
This unit would not extract, nor feed the next round when locked in a vise and fired from the remote position.
The following checks and repairs were made:
I installed +2 rollers (8.02 mm) and found the bolt gap was .005in.
This was acceptable but I wanted more gap
I then installed +4 rollers (8.04 mm) and got a gap of .008in
Each + roller adds .003in to the gap
With a go guage the gap was increased to .009in or .001in gain, well within the head space of the 7.62 X 51 cartridge.
With the no go guage the bolt gap was .012 a gain of .003in.
This is perfectly acceptable for the cartridge.
The use of the gauges merely assured the repairs were within limits of the Cetme for safe shooting of the unit.
It was test fired with 30 rounds of NATO surplus ammo from 3 different magazines with no failures.
Changing the brake to the original Cetme