I would like to build / buy complete a "precision AR/MK12" clone. I plan to be using factory ammo only, no reloading. Since IMI 77gr seems to be in good supply, what are people's experiences with various barrels / rifles and that ammo?

I am targeting 18-20" barrel, DI gas system (no piston).

I have Larue ultimate precision upper from 2017 that has OKish groups (1.1-1.5 MOA at 100, using 18X scope). However, I wonder if there is anything better. I had BCM MK12 MOD 0 upper years ago and was NOT impressed by its accuracy.

A 10-shot group group fired off the bench from my Lothar-Walther barreled AR-15 at a distance of 100 yards had an extreme spread of 0.95”.  20" barrel with a 223 Wylde chamber, 1:8" twist.




....

My Criterion Core lies IMI 77gr. It does about 1 moa, and I am sure with a better shooter or scope it could be even less.

I had a Larue Stealth 18" barrel that would shoot IMI 77gr razorcore under 1 inch at 100yards all day long.   I regret selling that upper but could not pass on the price i was offered for it.

My CLE-chambered Bartlien 1:7 shoots 77 Razorcore at ~0.75moa (can do slightly under 1/2moa with optimized handload)
My 16” mid-gas Criterion 1:8 shoots it right at or just slightly under 1moa

I’m using 5-shot groups as my reference.

I think the white oak SPR barrels are a steal for the performance you get.l and have always shot the heavier bullets well.  But I don’t have any razorcore to test with.

Load development:


MOA all day

I have used IMI 77 and a copycat hand load that I turned speed down just a touch.  Larue 18 and buddies criterion 18 both put them just under an inch.

I haven't tried grouping the Razorcore with my Douglas 18 inch barrel, but I was able to make a cloverleaf with my Lilja 16 inch. I don't have those fancy apps to measure it, but I think I have pic of it on my phone.