Hi I just replaced the rollers in my cetme with some +4 rollers from RTG. Before installing them I had zero bolt gap and less then a dime of cocking tube gap. After installing them I have zero bolt gap and my cocking tube gap is now zero as well. As soon as there is any resistance at all I can seem the cocking tube support touching the bolt carrier. Does anyone have any advice or know of a good gunsmith in Louisiana that deals with cetmes. Well thanks for your time.
It sounds like your barrel is pressed in too far and +4 rollers aren't able to take up the slack. What doesn't make sense is a negative change in the c-tube gap. A zero bolt gap is a zero bolt gap regardless of the rollers. The C-tube didn't get any longer in the process.
The only thing I can think of is that I cleaned that crap out of it when I put the new rollers in. I am not sure what to do to fix these issues.
Start with the stickies at the top of the cetme page. It sounds like you've already done some of them since you've made it through the cocking tube gap measurement.
Before you get too worried about finding a gunsmith start taking a good look at the bolt face, bolt over-all length, and front of the windows where the rollers come to rest at lockup. Look at locking piece shoulder angles for divots at the roller rest points, and the front of the carrier where the LP rests against it. Wear in any/all of these areas will also singularly or cumulatively decrease bolt gap significantly. Photos will probably be necessary for any of us to be much help.
Expense-wise, every one of these things can be replaced for much less than $100 so if it is a component issue it's worth diagnosing before shipping it off.
I will take some measurements and pictures tomorrow after work. I was wondering about replacements as well. Most of the stuff I have seen is used and the only new stuff I saw was at scorpion arms for $105 for the whole carrier & bolt assembly. I wasnt sure if this is the route to take. Anyway Ill get the measurements tomorrow with pics. Thanks for your time.
On my FA91, the cocking tube gap is hard to accurately measure because my cocking handle support is so circumferentially worn (or, more likely, was ground to move more freely in the charge tube) that it can rock and tilt in the tube giving a different gap reading depending upon how it comes to rest. I can always futz with its orientation to get a max gap reading (about 0.025 in my case).
My point is that the cocking tube gap reading you are getting may be a red herring, if yours is like mine, and may end up just fine once you get the bolt gap issue resolved.
(FWIW - I am a total noob, with a grand total of one months experience with this platform, so grains of salt are advised).
HK cocking handle supports are available for $7.50 at Apex, no need to mess around with a "modified" one unless it was modified for a reason.
I dont think my bolt is ground since it has the bevels on the back side of it. The measurements with a caliper of the bolt: Roller windows : 8.14 mm, I am not super confidant in that measurement. Over all Length: 46.53mm window to end of bolt short side: 15.08mm window to end of bolt long side: 23.35. The theoretical window space : 46.53-15.08-23.35 =8.1. The caliper I am using is good to .03mm haha damn it! The measurements in inches are 1.8335-.920-.595 =.3185 measured window gap .319. As far as the locking piece goes there is definitely wear and it seems like there is a good divot where the locking piece hits the bolt. I tried to take a pic but it sucks. My camera is a heap. Also, what should my +4 rollers measure? 8.04 mm? I think my calipers are just not up to snuff for the .01 mm accuracy stuff. at 8.03mm I can slide my +4 roller in and out of the caliper. The old rollers seem to be 8.03mm as well. Man this stinks, anyone have suggestions?
Get a better camera?Man this stinks, anyone have suggestions?
As for the bolt head windows, take the bolt head under a good light and tilt the bolt so the roller on that side falls back into the bolt head. Look at the front of the window to see if there is a visible dent near the opening where the roller hits when it's fully extended. Even on a bad bolt head calipers won't detect the divot. Then look at the front of the bolt head. Is there a bright metal "ring" where the face of the bolt has been hitting the trunnion instead of the back of the barrel?
There are two main possibilities. Your parts are extremely worn (only you can tell) or your barrel is pressed too far into the trunnion. You can replace the parts and it might (or might not) work.
Here is a bolt head that was hitting the trunnion instead of the back of the barrel for way too long. Along the line of the broken area you can see the bright circular area of the trunnion markings:
The front side of the roller window definitely has some wear. I kind kind of see a ring where you are talking as well but only when light is reflecting off it. Also I noticed the end of my bolt carrier isnt flat. There is some metal missing. Is this normal? Ill borrow a friends camera tomorrow for better pics but as far as determining the issue I would say the ring is inconclusive perhaps better pics will help but is there anything else that can help determine this before purchasing new parts? Thanks for all the feedback I really appreciate the help. I have had this gun for like 6yrs and shot it a bunch and never heard of this bolt gap issue until a buddy told me about it so I checked it and sure enough no gap. I also put my old rollers in to double check the cocking tube gap. After dry firing I had no gap. I must have not fired it the first time I checked it. If I dont dry fire there is definitely some play in my cocking handle support. Again thanks for the help.
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