that time again g3 bolt gap?

[DAA1]

What is the acceptable bolt gap for a g3 clone? If I did it right with the rollers I got from wild bill cody I came up with .016 on my feeler gauge. Good or bad?
By the way the cleaning tool that comes with an ak cleaning kit that looks like a little punch works great to remove the pin on the roller retainer plate..

[SSwee]

.005" to .020" bolt gap
.016" is very good
SS

[DAA1]

Thanks SSwee, and thanks again to wildbillcody for the retaining plate and other goodies. I will know for sure what the gap is after I clean it thouroughly and take it our for a test fire in a couple of months.

[Seattlefungus]

Bought one of the "New" last Century IA CETME. Out of the box, shot it, functioned fine. Then decided to check the gap. .004. Put in a new bolt, (Old one was not ground" new +4 rollers and a new locking piece. Now it's .012. So watch it, even on the "New" ones. Good thing I had a stock pile of parts..

[cimmaronkid]

Remember to measure your bolt head to make sure you aren't getting a "false" gap. Bolt head should measure 1.835" and be sure to check the gap on the cocking handle wich should be about .020".

[Seattlefungus]

Yeah, and the armorer manual says to also let the bolt forward from the full rear position then drop the hammer before taking the messurement.

[submarinedriver]

All,

I don't know exactly what you're talking about with the bolt gap mentioned. How is it taken? What is the condition of the weapon when it is taken (bolt cycled forward under "gentle" pressure or allowed to cycle to battery using full spring force)?

This also brings me to my next question.... What is the purpose of having the different sized rollers? I can imagine that when the gun experiences wear that the "gap" (as yet not understood by me) opens up and therefore larger (or the other way around) rollers are used to correct for the wear. I never shot the weapons enough to wear them out. The intention of the spare parts was to have in case of breakage but I never thought ahead to include wear and tear.

Sorry if this is a newbie question but I've seen it mentioned on the Cetme forum and I wanted to get "in the know" now.

Thanks for all the help I know I'll receive on this subject.

TACAMO,

Jeff

[Robert @ RTG Parts]

I don't know exactly what you're talking about with the bolt gap mentioned. How is it taken? What is the condition of the weapon when it is taken (bolt cycled forward under "gentle" pressure or allowed to cycle to battery using full spring force)?


Below is the directions from my website. That is how I measure bolt gap. The rollers, along with the locking piece, trunion and bolt create 'bolt gap' which is an easy way to ensure your rifle opens at the correct time; releasing the correct amount of energy for safe operation. Also, makes sure your gun does not go Ka'Boom.

Q: How to check your Bolt Gap?
A: For a HK91, G3 or Cetme to run reliably and safely it should have a bolt gap that measures between .3 and .5 millimeters (about .012 - .020 Inch). If your HK/G3 or Cetme has less bolt gap or no bolt gap than you need to change your rollers and use HK + Size rollers which are available for sale on our G3 Parts page. Do not think that just because your rifle is working that your bolt gap is OK. I myself didn't notice the bolt gap had totally disappeared on my favorite FMP G3. I was shocked to see I had no bolt gap, a set of HK +2 Rollers got me back up to spec and now I can once again safely shoot my favorite G3. The lack of bolt gap can not only be dangerous but it also increases the amount of wear that your rifle endures while firing.
1, Remove Magazine.
2, Pull back cocking handle and let the bolt slam shut, make sure it's shut all the way, pull trigger
3, Turn rifle over so you are looking into the bottom of the mag well.
4, Using a feeler gauge measure the gap that is between your bolt head and bolt carrier. If you lack a feeler gauge you can use one or two pieces of paper, though a feeler gauge is needed to obtain a proper measurement.
5, If you have less than .3mm of gap than you will need to acquire + size rollers which are available on the G3 page of this website. Then follow the instructions for the above topic titled "how to remove rollers" and replace your rollers.

http://www.robertrtg.com/g3.html

[Robert @ RTG Parts]

What is the acceptable bolt gap for a g3 clone? If I did it right with the rollers I got from wild bill cody I came up with .016 on my feeler gauge. Good or bad?

0.016" is perfect. The Germans used an acceptable range of .3mm - .5mm (.012" - .020") for full auto rifles. Most HK Semi Auto's were shipped with a gap of .3mm -.4mm.

[submarinedriver]

Thanks so much for the prompt reply. I'll be checking it out tonight.

Jeff

[MicroPilot]

What are the implications of having a bolt gap greater than .020"? Would this gun be safe to fire? Can this condition be corrected, possibly using the -2 or -4 rollers?

[drhall762]

:thanks: Robert

As one of the new guys I need every scrap of information I can get just to try and figure out what I don't know,

Dave :sniper:

[SSwee]

What are the implications of having a bolt gap greater than .020"? Would this gun be safe to fire? Can this condition be corrected, possibly using the -2 or -4 rollers?

It's all about timing. I can't tell you the problems of too much bolt gap. If it's not too much you can fix it with -2 or -4 rollers. When you check it you'll need to check the cocking handle gap also. I changed out a carrier working with the bolt gap on my CAI Cetme and was real happy with .018" bolt gap until I found I didn't have any cocking handle gap. The original carrier had been ground where it hits the cocking handle.
SS

[MicroPilot]

How do you go about checking the cokcing hadle gap? It appears to me that there is good amount of play between the cocking handle and the bolt carrier, but at this point I do not know exactly what or where to check.

[SSwee]

Lift the cocking handle just enough to clear the stud latch and see if there is any movement back and forth in the direction of its travel. There is not much needed. I think spec. is .020" max. Don't lift the handle any more than to get it over the lock or it will get into the cam and give a false gap.
SS

[MicroPilot]

Just checked and there is way more than .020", probably more like 1/8".

[SSwee]

Normally they're set up with about the same gap as the bolt gap. As long as it is not too tight and holding the carrier back or bang the heck out of the cocking tube assembly and you're not having trouble cocking it there shouldn't be anything to worry about there. If it starts to get hard to cock you'll know where to look. Did you ever get an accurate bolt gap measurement?
SS

[MicroPilot]

.028" fits easily and .030" doesn't fit at all. Unfotunately my feeler gauges are only in .002" numbers increments from .006" to .016".

So I guess I can say it's .030" <> .028".

[SSwee]

That's pretty far out of spec. Is this a new build or one you got already assembled? It may be borderline getting into spec with +4 rollers. Is the bolt ground? I should have asked in the beginning. Any measurement on the bolt head?
SS

[MicroPilot]

This is a CAI stamped receiver CETME I've had for a few years. I've shot it before with no issues, actually I've put several hundred rounds through it.

I don't have a measurement on the bolt head. How can you tell if the bolt head has been ground?

Wouldn't +4 rollers INCREASE the bolt gap? Don't I need to DECREASE the bolt gap to get into spec.

[SSwee]

The +4 rollers increase the bolt gap. If CAI built the weapon and it had bolt gap problems they ground the back of the bolt head to give a false gap. You need to disassemble the bolt carrier assembly and measure the bolt head length. A dial caliper will be accurate enough. It should measure 1.835". It may be a couple of thousandths shorter due to wear. If it has been ground and measures 1.824" you would deduct .011" from your measurement to get the true bolt gap. If you don't have calipers, most auto parts houses usually have some you could take it in and use theirs.
SS

[MicroPilot]

I have a bolt length of 46.9 mm or just a tad over 1 13/16".

I don't have a more accurate micrometer on the moment.

[SSwee]

Well the 46.9mm is 1.849" and 1-13/16" is 1.812". Not close enough to tell. Have you had any luck finding -2 or -4 rollers?
SS

[MicroPilot]

No luck on the - size rollers. I've posted a WTB on here.

I'll be going to the Knob Crekk Range machine gun shoot in a few weeks and will hopefully be able to find them there. While at KCR I'll also be on the look out for other spare parts.

I'll keep searching the net for the rollers in the mean time.

I remember seeing instructions on the old site about removing the rollers. Has that info made it back onto here? Do I just punch the roll pin on the bolt in and remove the rollers and plate?

[jfowl31]

something just dont sound right here.....

bolt length is 1.849 which is .015" LONGER than normal.
bolt gap is .029" which is GROSSLY out of spec

it aint adding up. Ive never even heard of a cetme bolt being 1.849".

For info's sake... a larger than spec bolt gap CAN mean that the bolt is not getting sufficient lock up, and is unlocking too fast when the round is fired, and thus the pressures are too high when the bolt is unlocked. Recoil should be higher than usual, and you'll wear out your internals faster as everything is moving so much faster than its designed to.

See if you can get some new calipers, or use someone else's who are verified to be correct, and maybe even get some new feeler guages... something just sounds fishy here what with the longer bolt, and HUGE bolt gap and all.

also, if youve got 1/8" gap between your cocking handle and carrier, it should be REALLY hard to unlock the rifle.with that gap being so large, the camming action of the charging handle doesnt really unlock the bolt, and you have to use your own force to finish off the unlocking process.

maybe you should start a new thread micropilot with this weird info, and maybe get some more interest in it. I know Im all begoggled and befuddled about the numbers you posted.

[MicroPilot]

I agree on my needing to use different measuring instruments. I'm pretty confident in the bolt gap measurement, not so much on the bolt length. I will get a better measurement tomorrow.

It is difficult to cock the gun and the cocking lever does NOT unlock the bolt.

[SSwee]

If you find any -2 and -4 size rollers I'd be interested in some also .
SS