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Old May 16, 2012, 15:49   #1
Abominog
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Century CETME roller question

A friend got a cheap Century CETME.

It is a real bear to cock- not HK difficult, but has to be slammed.

The tube is straight, sights are straight. There is some significant binding between the receiver rear and bolt carrier, but that's not the cause of the cocking problem.

The bolt gap measures .025.

Will rollers fix the cocking problem? Which size does he need?

Thanks!
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Old May 16, 2012, 16:24   #2
Tim Dreas
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Quote:
Originally Posted by Abominog View Post
A friend got a cheap Century CETME.

It is a real bear to cock- not HK difficult, but has to be slammed.

The tube is straight, sights are straight. There is some significant binding between the receiver rear and bolt carrier, but that's not the cause of the cocking problem.

The bolt gap measures .025.

Will rollers fix the cocking problem? Which size does he need?

Thanks!
With the H&K and the CETME the gap between the cocking piece and the bolt carrier or "cocking clearance" can make it difficult to cock. If the cocking clearance is too wide it will be difficult to cock as the leverage of the cocking handle to unlock the bolt is lost. I'm not sure what the gap should be. Maybe -0.010" to 0.020". You can put a coin or washer between the cocking piece and the bolt carrier and check if it is easier to cock. If so, you can weld a washer or disk on the rear of the cocking piece.
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Old May 16, 2012, 18:58   #3
Abominog
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Thanks Tim.

I know gap should be .012 - .020.

Anybody know what size rollers are needed for a .025 gap?
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Old May 16, 2012, 21:42   #4
Tim Dreas
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Originally Posted by Abominog View Post
Thanks Tim.

I know gap should be .012 - .020.

Anybody know what size rollers are needed for a .025 gap?
Not the bolt gap. The gap between the front of the bolt carrier and the cocking piece. Put something down the tube to close the gap. This will make it easier to cock. The problem is the cocking tube is welded too far forward, so the handle isn't levering the bolt unlocked like it should.
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Old May 16, 2012, 23:21   #5
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i just fixed a buddy's cetme that the cocking handle's pin had walked out just enough to cause some resistance. it would bind slightly and wouldnt want to go fully into battery. i gave a couple taps with a punch and it fixed it right up. may not be the same issue but it may be worth a look.
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Old May 17, 2012, 07:20   #6
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Originally Posted by Tim Dreas View Post
Not the bolt gap. The gap between the front of the bolt carrier and the cocking piece. Put something down the tube to close the gap. This will make it easier to cock. The problem is the cocking tube is welded too far forward, so the handle isn't levering the bolt unlocked like it should.
Ah, yes.

We'd noted that. In fact, as one pulls the handle up it can be seen to push the B/C to the rear, but then a strange thing happens, the handle reaches its camming apex, and as one fully pulls the handle up it actually goes past the apex and lets the B/C come forward ever so slightly.
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Old May 30, 2012, 09:15   #7
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The cocking lever actually does act as a cam for the first small increment of movement. The problem is making the timing of the cam meet with the needs of the bolt to unlock. Small shims may be placed in the end of the cocking tube to adjust. Be sure that when the lever is down there is no contact with the tube end/shim. Also, take the rifle apart and give it a real good cleaning to include the interior of the tube. A bore brush of appropriate size works well as well as flushing with steam from a pressure steam cleaning tool. (these household tools are wonderious for cleaning military firearms of decades of dirt and grease) Century left great amounts of metal particles from the machining of the gun and the cocking was greatly impeded. Grease the cocking mechanism before reinstalling. Also be sure the bolt/rollers are in spec.
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Old May 30, 2012, 09:39   #8
gunplumber
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set cocking handle gap .001-.022"

The correct way is to cut off and set back the cocking tube.

the workaround is to solder a washer to the cocking handle extension.

Try some -2 rollers as your bolt gap is excessive as well. Should be .1-.5mm. I set to .020" when possible, which is .508mm - like locking shoulder setback it usually drops to .019 (.5mm) on initial firing.

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Last edited by gunplumber; May 31, 2012 at 10:09.
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Old May 31, 2012, 08:51   #9
Abominog
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Quote:
Originally Posted by gunplumber View Post
set cocking handle gap .001-.022"

The correct way is to cut off and set back the cocking tube.

the workaround is to solder a washer to the cocking handle extension.

Try some -2 rollers as your bolt gap is excessive as well. Should be .1-.5mm. I set to .020" when possible, which is .508" - like locking shoulder setback it usually drops to .019 (.5mm) on initial firing.

http://www.arizonaresponsesystems.co...ild/tube09.jpg
Thanks Mark, that's the answer I was looking for.
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