View Full Version : Fitting lower.

September 30, 2001, 11:46
I've noticed on one of my FALs that there is a bit of play at the pivot point where the upper and lower connect, from the lower being slightly out of spec or the pivot bolt being too long.

Is it safe to take some thin washers and shim this out? By feeler gauge, its about .005 gapped.

September 30, 2001, 12:00
Can you be a little more specific about where the "play" occurs.

Is the pivot pin undersize?
Is there slop between the upper and the lower when the two are locked togeter?
If so is the slop up-down or left-right?

September 30, 2001, 12:10
The pin seems to be the right diameter. It just seems long, the threads bottom out before the pivot becomes remotely tight.

The play is left-right, and is lessened when locked toghter, but enough that it can still move.

I checked over the latch and it seems secure, and theres no up-down play whatsoever.

September 30, 2001, 15:37
The first thing I'd do is start swapping lowers to narrow down the offending part. Do all lowers exhibit this play? Then it's your receiver; the pivot area is out-of-spec, too narrow. Repair Method #1. Does this lower exhibit the play on all receivers? Then it's that lower; a stupid recruit or an Angry Beaver got impatient or careless during a breakdown and twisted the lower off, bending open the pivot tabs. Repair Method #1 or #2.

Repair Method #1: use one thin washer, or two REALLY thin washers. For consistency, I'd glue the sucker in place.

Repair Method #2: now we test your cojones. Place the lower's pivot tabs in a vice and GENTLY compress. Test fit often. You're trying to slowly bend the tabs back into spec, not crush the lower. (Obvious, but the legal department made me say that.)

--Radio (with edit due to another keyboard AD)


"Very damaged. Zathras can never have anything nice." --Zathras

[ September 30, 2001: Message edited by: Radio ]

September 30, 2001, 15:43
OK. So, the pin slops from side-to-side when its fully tightened. Isn't that better than the alternative?

I guess if the slop is extreme, you could shorten the overall length of the female half so that you can screw it in further before the female half bottoms-out against the male half.

In any event, this problem is no more than cosmetic. So long as the upper and lower lock-up solid, your front-sight / rear-sight relationship should remain constant.

September 30, 2001, 16:29
I used Radio's fix #1 with two .003 shim washers. The results: The upper and lower now fit with no motion in any direction. It also brought the exterior edges of the upper reciver flush and aligned with edges recoil plate. (it wasn't before, due to the lateral play.)

September 30, 2001, 22:02
I used method 1. Worked like a charm. Now I have more consistent groups.