XCR-M maintenance

R

Roddy

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I recently purchased a lightly used XCR-M. It did not come with a manual but I found one online. The manual does not cover everything and the XCR thread and a forun search didn't have all the answers I was looking for.

I had a few issues with the bolt failing to go all the way into battery. Sometimes it was a feed issue from the crumby five round metal mag but it happened with Pmags too. Is this common? Does it just need more lube on the bolt group? Can the feed ramp be polished or anything?

I mounted a 2.5-10 scope on the rifle and had an issue with wandering zero. I think this is because of the Burris PEPR non quick release mount. I was able to rotate the screws by hand after a bit of shooting. If that wasn't it is there anything that can cause this? My new mount is in the mail so hopefully that fixes it.

Lastly the Allen screws. I keep hearing about loc tite for the XCR-L. I don't know how serious people are or if it is necessary for the M. How important is loc tite and how important is it to use the right amount of torque? I am planning on buying a torque wrench. The barrel screw in particular concerns me.
 
I am on the second highest gas setting. I moved it up one notch when it started having problems. The casings still eject the bolt just doesn't go home all the time. When I pull it back and le it go it almost always closes though. I am shooting mostly Norinco steel cases copper washed ammo.

I tightened the barrel retention bolt before I left to go shooting. It moved around an inch or two at 50 yards. I tried chasing it by adjusting the scope and just get frustrated.

I will take pictures of the bolt carrier group when I get home.
 
Hmmm. After break in I moved down from the plus the next setting and all was fine. Shot a few then bumped it down 2 settings and i had issues like u describe. Back to 4 and it went great, the gas block cap keeps loosening off so i may not be tightening it to spec. Check that front bolt on the gas block too.

I lubed the bcg a ton during break in as i had the bcg lock up. Every round since has been great and i leave a little more lube on the bcg when i put it back together.

I'm using the nori stuff too. No fail to fires and only a couple fte while messing with gas settings.
 
I mean I get a group, reload and the next group has moved considerably. It may just be my shooting. I think it is the mount tough because I had my Vortex QD on their before and it got better groupings with a lower powered scope.
 
I am buying a torque wrench right now. I was iffy about the PEPR mount as soon as I tried mounting it. I was not surprised when it shook loose.

Also I don't think it's the extractor that is keep the bolt from going into battery as it hangs up almost in the fully open position.
 
Roddy said:
I am buying a torque wrench right now. I was iffy about the PEPR mount as soon as I tried mounting it. I was not surprised when it shook loose.

Also I don't think it's the extractor that is keep the bolt from going into battery as it hangs up almost in the fully open position.
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Double check that gas cap on the front gas block... mine had loosened off.

My manual says 200 inch lbs for the front barrel retention bolt.
 
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Well there's the bolt. I don't think anything is wrong with it. Like I said earlier when the bolt fails to go home it usually ejects the spent casing then only moves a fraction of an inch forward. I'm hoping it just needs lubrication or something.
 
CosmiC10R said:
Double check that gas cap on the front gas block... mine had loosened off.

My manual says 200 inch lbs for the front barrel retention bolt.
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The manual that comes with these rifles is wrong and Rob Arms is supposed to be correcting it. The recommendation for the proper torque setting on that bolt is 250 inch pounds, not 200. The manual also says to break the rifles in with the gas setting on the highest, which is also incorrect. The recommended procedure for that is to turn the gas setting as low as you can and have the rifle still cycle properly, then after a few hundred rounds, see if you can turn the setting down even further if possible. You wouldn't take a brand new car and run it at redline for the first 4000km so why do it to your rifle.

The point on checking the tightness of the gas block is a very good one as well. You don't need Loctite on the rifles. The comment on checking the extractor is a good one as well, if the "extractor spring" is starting to go it can cause what you are experiencing. Also these guns really like to be run wet. Lube them up very very well. Also make sure that your barrel is seated properly.

The problem you are having with the bolt not locking up, does it do it with no magazine in the rifle or only when a magazine is inserted?
 
The bolt does not go home when it is chambering a new round. It ejects the casing and then stops right around when it hits the the next round in the magazine. The bolt has about 1/4" of play rearwards. I either pull it back that little bit and let it go or I can push is the charging handle and use it like a forward assist. So to answer your question only with a loaded magazine and only when the gun is cycling itself. It almost looks like the bolt hold open is engaged but its not.
 
Roddy said:
The bolt does not go home when it is chambering a new round. It ejects the casing and then stops right around when it hits the the next round in the magazine. The bolt has about 1/4" of play rearwards. I either pull it back that little bit and let it go or I can push is the charging handle and use it like a forward assist. So to answer your question only with a loaded magazine and only when the gun is cycling itself. It almost looks like the bolt hold open is engaged but its not.
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Send an email to sales@wolverinesupplies.com and in the subject line put Attention Grumpy. In the email include the symptoms you are describing and the serial number of the rifle. I will be happy to see what I can do to help out.
 
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