Recent AR Build: A few problems

[chrischris]

Hi Guys,

Spent some time at the range today with my recently assembled AR. I used what I believe was a RRA lower parts kit on a Stag lower with a Sabre Defense upper receiver, with a PMAG.

1.) The magazine doesn't always lock back after the last round. I used a wide variety of magazines (various GI mags and PMAGS) and sill have inconsistent results. I noticed that when I separated the upper and lower receivers and loaded a magazine with a shell casing, and slide the casing out, the bolt release didn't max out (I am able to move it slightly before it maxes). Could I perhaps have too strong of a spring?

2.) My hammer pin kept working its way out, resulting in my hammer group shifting to one side. My rear takedown pin is still very very stiff (requiring a punch to remove it), could my hammer in hole be out of spec on this lower? Should I get some "anti walk pins"?

Other than those to issues, everything functioned well with no misfires, doublefeeds, or failure to eject issues.

Any advice would be appreciated. Thanks,

[ryan]

Skip the "anti-walk" pins and get a G&R Tactical LPK and go ahead and order a DD stripped lower and rectify the problem properly

[Belmont31R]

Skip the "anti-walk" pins and get a G&R Tactical LPK and go ahead and order a DD stripped lower and rectify the problem properly


He likely doesnt need to do any of that.




OP-


Take the unloaded mag (do you have more than 1?), insert it in the weapon, and pull the CH back. Does the bolt lock back? If it doesn't take the upper off, and insert the mag. Is the little pawl on the bolt catch making good contact with the follower or is it short? We can work from there.


Edit: RE the hammer pin...if you can take the pin, and hammer out. Insert the pin only. Is it loose in the hole or is there some resistance? Also just to make sure the legs on the hammer spring should go over the trigger pin. On standard pins there will be a groove on one side. One leg of the hammer spring should go in that pin. Its not uncommon in my experience for there is be some movement of the pins but its generally very small. It doesnt walk out more than a MM or so. I just push em back in when I notice it.


The rear takedown pin being tight. It should loose up with some use. If it doesnt you can try another pin.

[Quib]

- Remove the hammer pin and hammer.

- Check inside the hammer for the presence of the J-spring. The J-spring is what catches the center groove in the pin used for the hammer and retains the hammer pin within the lower receiver. If the hammer J-spring is missing or incorrectly installed*, the hammer pin will walk.

*Take a pick or scribe and attempt to push down on the J-spring. See if it will seat farther.

- Another possibility is the groove in the hammer pin is too shallow to hold the J-spring. In this case a temporary fix may be to take a jewelers file and deepen the groove. (This has worked for me in the past.)

- In the case of the above, the permanent fix would be to replace the hammer pin.

[chrischris]

Thanks guys for the help I removed the hammer and pin and push down the j spring. I hope it is seating correctly, but I will keep an eye on it.

Regarding the bolt not locking back, yes the bolt locks back on an empty magazine when I pull the charging handle. It even occasionally locks back after the last round is fired. However I am getting inconsistent results. I have tried multiple magazines with the same result. With just the lower receiver, after inserting a magazine with one round in, and removing the round, the mag plate doesn't force the bolt catch to the maximum position. I tried on another AR (that locks the bolt back) and found that under these conditions the other lower maxes out the bolt catch.

Any ideas?

[Quib]

Thanks guys for the help I removed the hammer and pin and push down the j spring. I hope it is seating correctly, but I will keep an eye on it.


Does the J-spring have any play in it? If you take a pick or scribe and pull on the tail of the spring, does it pull out? If so, the spring may not be fully seated and peened correctly in place.

[Belmont31R]

Thanks guys for the help I removed the hammer and pin and push down the j spring. I hope it is seating correctly, but I will keep an eye on it.

Regarding the bolt not locking back, yes the bolt locks back on an empty magazine when I pull the charging handle. It even occasionally locks back after the last round is fired. However I am getting inconsistent results. I have tried multiple magazines with the same result. With just the lower receiver, after inserting a magazine with one round in, and removing the round, the mag plate doesn't force the bolt catch to the maximum position. I tried on another AR (that locks the bolt back) and found that under these conditions the other lower maxes out the bolt catch.

Any ideas?


RE the lock back issue. Id order a Colt bolt catch, spring, plunger, and bolt catch roll pin from Colt. That way you get quality parts, and the issue will likely resolve itself.

Edit- At the same time you can get a couple FCG pins (Colt), and replace those. They are cheap...

[chrischris]

It doesn't seem to be moving much. However it is very low and recessed in the cutout. Is it supposed to protrude outside of the cutout?

[Belmont31R]

It doesn't seem to be moving much. However it is very low and recessed in the cutout. Is it supposed to protrude outside of the cutout?



All of mine protrude slightly out. Maybe 1MM or so if I rub my finger across the top.


Can you post a pic?

[Quib]

It doesn't seem to be moving much. However it is very low and recessed in the cutout. Is it supposed to protrude outside of the cutout?

Sounds GTG. It should be recessed into the cut-out and not have an excessive amount of play.

Try pressing down on it to see if you can get it to bend more in towards the center of the pin axis. That might help hold it in the pin groove if the problem does not lay with the hammer pin groove depth as I mentioned above.

[chrischris]

http://i50.tinypic.com/23kd64x.jpg
http://i50.tinypic.com/2q3b4nt.jpg

[chrischris]

How does this look guys?

[Iraqgunz]

You need to look into the hole where the hammer pin goes through and see how much of the spring you can see.

It is entirely possible that some of the parts are out of spec. I had a conversation today with the owner of a shop in Tempe, AZ and he told me that they recently had to send back 4 RRA lowers for various issues.

You also need to ensure that you are assembling everything correctly. Install the trigger parts first and then the hammer. The legs of the hammer spring go over the trigger pin. Then install the safety selector lever.


How does this look guys?

[Quib]

You need to look into the hole where the hammer pin goes through and see how much of the spring you can see.


This is what I'm getting at Chris.


From the pics above, the J-spring looks fine. Take a pick or scribe, a small flat-tip screwdriver might work as well, and try pushing down on the J-spring. Attempt to push it more towards the center axis of the hammer pin hole.

Use your hammer pin to gauge your progress. Occasionally insert the pin to see if you're increasing the J-spring tension by pressing it more towards the center of the hammer pin axis.