Yikes. I had to do that once. Couldn't get the muzzle device off and took it to this old fella. He literally told me I might want to look away. lol

I have tried a couple uppers on this lower, Colt 6920, PWS, and a Noveske/LaRue build and haven't had any issues yet. My 22lr conversion uppers are a different story, they won't hold open with the right side controls. I can live with that.

For my purposes this LWRC (without having shot it yet caveat lol) fits my needs perfectly. It is light, slim, great handguard, the ambi stuff works perfectly for me. I always have been aggravated by attempting clearance drills with a standard AR. I never got the hang of the drill. My fingers just are slightly too short to make it comfortable. A BAD type lever fixed all that but it is not an elegant solution. Ambi lowers are an elegant solution.

SCAR's are crazy. I might one day end up with a 17 but there is absolutely no way I would pay 16 prices.