wgj3

I wanna bring back cutoffs!

Looks like that upper has a proprietary handguard... Are there options?

Light BCG isn't ideal for what is likely a fairly over-gassed rifle... As previously mentioned, barrel is most likely place to save a bit, turn it down some, shorten it, lighter gas block, lighter comp. What handguard? Aero?

Steiner is decidedly better optic!

Gun that fits you best will have least "felt" recoil.

Would running 9mm be staying with the spirit of the rule? Seems projectile diameter would allow it. 9mm "technically" has a rim...

Replacing rear sight on what firearm to be used for what purpose?

HazedCustom

New plug needed so that it has a way to stay in place without the bushing retaining it... May be able to use same actual guide rod.

That is correct, Grump.

HCRI

Same stuff for any other 9mm with minor ammo. There's about a 100 ways to make it work and that projectile should be fine. The RN profile tends to feed well.

So says you, but what do you know...?

What about a mag catch that holds the mags a touch higher like the Dawson...?

I've tried a number of different options including a couple mentioned in this thread. Not sure what is really the best answer though... I'm with many other in that I bring mixed brass home in 5 gal buckets. Sort once filled. Have a bunch of the kitty litter buckets for .223 brass mostly. Various other containers for 9mm, .38Super/SC, .40, .45, .308, .44 Mag/Spec, etc....