I picked up a 450 AR upper a few months ago and I'm in the process of building a lower for it. I'm curious who has used one, specifically what triggers, buffers/Springs, and optics were used and liked.

So far all I have is the upper and a spikes stripped lowers so this is a from scratch build.

I have a 450 bushmaster.



100 yards 2 sighters and 3 for group.

I built one.   I'm using a Timney trigger, a heavy buffer and a Falcon Menace 1.5-6. Attached File

I have a Stag Arms 3TL and got an Bushmaster 20" upper. I have a Geissle SSA-Eric trigger, JP Tuned spring, Spikes T2 heavy buffer, Ross Muzzle Brake, and a Vortex Diamond HD 4-16x42 on a Burris PEPR. Crazy accurate and the recoil is minimal, great and fun gun to shoot, alittle loud and turns heads at the range. I hunt in  the shotgun zone also in Michigan. This took place of my H&R 12 gauge Slugster. (Still is a great gun)

The 450 uppers seemed to work with both rifle and carbine systems . This is with Trident and Bartz uppers .
Black gun 450's work but I'm more of a bolt gun guy.

RRA 4.5lb National Match trigger is my favorite go-to. It's easy to shoot precisely with and smooth for quick shots while being lighter than anything "GI". Also pretty good price wise and can be found on sale surprisingly often.

Buffer wise I'd go with an H buffer for carbine, or a normal rifle buffer with a tubb's flat spring for rifle. Personally I like the carbine setup, since I like a stock just a bit shorter than the A1 length, but whatever fits you best is what's good.