hey pal, just what you see here.

This unprecedented range of bullets weight and design make the AR500 suitable for anything from prairie dogs to pachyderms to Peterbilts. Truck stopping power in a platform weighing less than 10 pounds.

lolwut

They hired the 6.5 Grendel's hype man and told him to step it up a notch.

THAT'S WHAT SHE SAID

If we put an entire AR-15 in a 406mm casing... does that still count?

Just thinking outside the box here.

I don't know what the OP's criteria are, but in the pre-pandemic salad days, I was seriously considering a 358 Yeti for the perfect big bore AR-15.

Load data shows 200 grain bullets at 2,500 MV and 180 gr at 2,600 fps from 16" barrel and a slight gain from an 18" barrel. Load data for rifle bullets from 180 to 250 grains (2,100 fps) and can also load .357 pistol bullets for considerably less expensive plinking ammo (140 gr Hornady FTX runs nearly 3,000 fps).

Uses .308 cases, and 6.8 mags (mixed results with others) so components are relatively easy to source and are more affordable (free at some ranges). Uses a proprietary bolt and barrel extension that come with the barrel, and a set of Custom Hornady Full Length Dies can be included as well. There were a couple sources for loaded ammo, but not likely now. Would have to find a suppressor rated for .358 bullets and 60k psi though.

You didn't specify "AR cartridge" (ETA: you specified AR Lower, so my mistake) so I'm going to have to nominate the 2 Bore.

Giles Whittome and his 2-Bore rifle "Tyrannosaurus".



Left to Right: .303, 500 Nitro Express, 600 Nitro Express, 4 Bore, 2 Bore.