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Discussion Starter #1
Hi Folks,

During another great day at the range, the hammer (axis?) pin started slipping out each time I fired 5-10 rounds. I could push it back in, gun operated fine. But it was slipping out from the vibration.

So I stripped the rifle and looked around inside, and noticed a cotter-pin-type hole in the pin that was slipping. It looks like it lines up with and would fit the spring that wraps the trigger axis pin. So I disassembled the whole trigger group, thinking that somewhere, somehow, there would be information I could find on how to put it back together. Not like the thing is that complicated.

After fiddling around for over an hour, and searching around the net for even longer, I cannot find any sort of schematic or disassembly guide for the trigger group. On top of that, I can't even find a downward-angled picture of the lower receiver, just to get a sense of properly-ordered spring placement.

Does anyone know where I can find this info?
 

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Here is what I have, got this last year from Robarm when they had a few problems with the early runs (Aug 06). hope it helps.
 

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From memory,the tails of the hammer spring hold the trigger pin in place. There should be recesses in the pin on either end. The Hammer pin is then held in place by a cotter pin on the left side just inside the reciever.

Sorry, it's from memory as the XCR is at the back of the gunsafe.
 

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Not an expert, but that looks functionally very, very similar to a standard AR trigger group to me. I assume the "cotter pin" in that XCR diagram somehow serves the same role of retaining the hammer pin that the J-hook serves in a standard AR group?

I'd get some AR15 lower instructions and see if I couldn't assemble/dissassemble the XCR group in the same way. Then call RA if that doesn't do it.
 

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When I was studying this over the weekend I noticed that my cotterpin is pushed all the way down. So the loop in the pin is just about even with the hammer spring. If I was not looking closely it would have looked like the spring had a bulge.

I can't see how it would come out, but anything is possible.
 

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Discussion Starter #9
Hi Folks,

Thanks for all the responses. I did figure it out, and (finally) had a great day at the range last Saturday.

The original problem was that the hammer pin cotter pin had come out. I actually had found it the same day I started having problems with the trigger group, but I didn't know what it was or where it went so I just bagged it and put it away. Took apart the entire trigger grouping (everything except for the safety axis "cylinder", which I still never figured out), inspected for wear marks to deduce spring locations, and tried to put it back to together.

Before I learned of the missing cotter pin, I noticed that the long end of the trigger spring could potentially line up with the cotter pin hole in the hammer axis pin. Lost at least an hour or two trying to manage that silliness!

Once the cotter pin issue was resolved, the key problem I had was understanding where the trigger (return) spring went. I only have 1 XCR, and despite all the pictures of XCRs online, not a single one shows the inside of the lower receiver, so I had no reference points. There were two potential places where the elbowed end of the spring could go.

Because I never figured out how to get the safety axis "cylinder" out, I couldn't get the trigger out, so I never saw any spring wear marks on it (I would have, though). So I kept trying to put that elbow in between the 2nd-stage/whatever part (that shares the trigger axis pin) and the trigger itself. There were definitely wear marks there. But it didn't work; it kept slipping out (because that's not where it goes). For anyone else with a similar problem, the symptom was that the trigger didn't return forward.

Interestingly enough, this mistake had a very curious side effect: when that 2nd-stage/whatever piece wasn't properly engaged, the weapon fired in what appeared to be full-automatic mode. I wasn't going to sit there and experiment with it, but it did seem odd that something so simple could have such a drastic effect.

Anyway, I eventually figured out that the elbow end of the trigger spring goes underneath the trigger. Once that was done, the familiar pull tension returned to the trigger and the weapon worked normally.

To the other commenters

ny32182: The trigger grouping is very similar, true, but I don't think the trigger (return) spring is. I'm not at home right now, but I did exactly that (I have two ARs) and was stumped. (My first attempt at placing the elbow end of the trigger spring is what I think cost me so much time, because it technically worked under dry firing conditions).

va_plinker: yeah, that's exactly what happened -- somehow the cotter pin had worked loose.

Suggestions

It would be great if there was a trigger schematic available from RA at some point -- they sell replacement parts, but no directions for how to put them back together?

Lacking that, I really think some simple, clear pictures of the inside of the receiver -- maybe 4-5 showing each stage of assembly -- would be plenty enough for anyone in this position.

Also, a much smaller side comment -- most of my early break-in "issues" were the result of screws not being locktited, etc. I have read, understand, and agree with the RA philosophy about how to break-in a rifle, but there wasn't really a heads-up in the manual for "pieces coming off" (like the Ejector on the upper receiver). Might be good to include a supplementary note to people about this, and maybe a complimentary tiny bottle of locktite or similar?


Thanks everybody! And a huge thumbs up to the lighter barrel with the simplified gas adjustment! My XCR LBAR is a good 1-2lbs lighter than my similarly equipped AR carbine.
 

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If you want to remove the safety selector then you need to remove the pistol grop. There is a small hole under the reciever that contains a pin and spring which control the movement of the selector. This is held in place by the pistol grip.
 

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Discussion Starter #11
Ahh, just like the AR's rear takedown pin spring detent. Got it, thanks!

cheers.
--jordan
 

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The rear take down pin detent on an AR goes in through the rear of the receiver under the endplate. If the XCR has its selector detent held in by the pistol grip, that is also very AR-similar.
 
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