I have an old mil-spec A2 upper that has a fairly loose hand guard end cap (triangular) that has copious side to side movement. This makes for a fairly annoying level of rattle. Anyone know of a quick fix with a shim or the like? Research shows that this is almost universal with the original full length A2's, and remedies abound on the webz, but I thought I'd ask the SF brain trust for the best option...

we use to just shim them with sticky shim stuff that we also used to time the flash hider/compensator...

vaguely I think it was called a peel washer.....I could be wrong. it's been 20 years or so....

I knew someone would chime in eventually; I thought about using a crush washer (same as peel I suspect) but the clearance is fractional. My other "fix" thought was brazing the cap to the barrel as it would be minimally intrusive. That, or living with the battle rattle.