Besides the usual suspects for obtaining one of these, can any one point me in the right direction?

Post a a WTB thread and nothing.

Shipping from AA is ridiculous.

These things were a dime a dozen not too long ago.  Where have they all gone?

you could dremel a regular round M4 handguard cap.  just provide clearance for the op rod.

I may help you with the cap if I can find my AA box.

You can go Magpul Moe foregrips.  They are GP compatible.

Thanks guys!

I was never happy with AA's cap method. They chop the top out to clear the piston. That means there is nothing to stop the round (mine came with round) cap from rotating (since there is no gas tube running through it). Normally that wouldn't be a huge deal except try this... pull the piston back, and rotate the cap, then let the piston go. Yes, now you have a piston not fully seated forward (the cap is exactly where the piston meets the block and can wedge in there). If not that, the cap scrapes the hell out of the piston side... ask me how I know

Have you experienced that malfunction?

Normally, that is a problem only if you tend to shoot without the hand guards installed.  The two little dimples on the sides of the cap should provide sufficient centering for the cap.



In an Army test of standard kits, totaling nearly 13,000 rounds fired, about 40% in full-auto, there were no mention of this type of malfunction either.

Yeah, when assembled, the handguards will keep the front cap from rotating, since they are prevented from rotating by the teeth of the barrel nut.