Found some damage on on of my XCR-Ls this weekend. Started getting FRB issues and hard extraction. Then It started double feeding. Stripped it down and found the cam lug peened badly. Waiting on Robarms to get back to me about this. 1k through it. Ever seen this before?
Found some damage on on of my XCR-Ls this weekend. Started getting FRB issues and hard extraction. Then It started double feeding. Stripped it down and found the cam lug peened badly. Waiting on Robarms to get back to me about this. 1k through it. Ever seen this before?
What does the ejector look like? From the pics it appears the bolt was rotated slightly during the feed stroke; the portion of the cycle when that surface is engaged. A loose or misaligned ejector could influence the bolt at that point.
You may be able to true that surface (as well as it's mating surface on the carrier), but you will want to ensure the ejector is correct before dropping the bolt with any force.
Edit: Also, what does the mag that was in use look like at the BHO area?
The bolt is certainly not the cause of the damage. Until you're certain the cause has been addressed, I would not allow the bolt to drop home. You might try sliding the BCG (no recoil spring) back and forth in the upper so you can watch the bolt as it meets the ejector.
You didn't include pics of the carrier that show the engagement surface well, nor the face of the bolt. With that kind of damage on the bolt, I'm guessing the carrier is also damaged.
It's not a matter of simply being loose though....did you check to make sure it is properly aligned to the groove in the carrier (with the bolt installed)? If you haven't, do the test Mechanic mentioned (though I usually just take the lower off the upper, flip the upper upside down on a table and drag the carrier bolt and piston assembly out via the recoil spring). The "official" test by RA was that if the recoil spring came out of the piston/recoil rod, then there was drag in the system somewhere that could lead to short strokes....but it will also tell you (as you'll be able to see it happen) if the ejector isn't properly aligned to the groove in the bolt/carrier.
They look identical. I also have a 300blk in the micro config and it looks the same as well. Wonder if it didn't get heat treated. I could do a hardness test to check. I'm guessing it's 4140? Should be between 40-50 HRC?
I've had an OOB situation in a -L, and there's no heightened awareness needed - I knew it like I knew the alarmclock went off to wake me up this morning.
On the good side, the bolt didn't appear to be damaged - on the bad side, the carrier was damaged.
Back on the good side, Nate had everything I needed to turn that carrier group into spare parts, and have it up and going again soon.
Probably would have run fine with the mooshed carrier, but I figure "why chance it if I don't have to?"
All that aside, Mechanic has given you some good advice IMHO.
Understand that if it was TiN coated, it was exposed to high heat. Very possibly high enough to draw back the heat treat. I can almost guarantee that is your problem.
TiN is deposited at 800F. 4140 anneals 1600F. Don't think this is the issue. My shop processes 50-100 TiN bolts per month. Never had an issue with AR, MPX, MCX, AK, 556xi or any other bolt with this process.
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