Here's mine.
21" Saiga with 4-12x Bushnell Banner scope and Tapco trigger modified for 2-stage action.
19 rounds of Brown Bear FMJ in a 4.5" group with the scope a little loose.
The best group I've shot with a AR was 5-shots in a 1.05 inch group using a Bushmaster 308 ORC with match ammo at 100 yds. Another 5-shot group had 3 rounds touching with a group size of 1.77 inches.
They will run just fine. The recoil is similar to most 3 1/2" shells. I've already had to run quite a few rounds of these through Remington 870s, 1187s, and their new shot gun. They start to hurt after about 15 rounds.