What ammo is the most accurate in my rifle?
Last Updated :: 7/28/2010 10:51:42 AM EDT

Not to be cheeky, but the answer is "it depends". Are you looking for a hyper-accurate round, or just something off the shelf that shoots well? People's definition of "accurate" varies quite a bit. Some people would call a 1.5" round at 100 yards accurate, while others wouldn't be happy with anything larger than 0.5" at the same distance. To obtain the absolute best in accuracy, you'll have to try it in your rifle and experiment. If you're just interested in some loads that others have been happy with, then here's some recommendations. The list is not all-inclusive by any stretch of the imagination, but should give you a starting point:

1:7 Bushmaster M4A3 (EOTech 511) Mk262 Mod1 1.25"
CMMG 20", scoped XM193 1"
LMT M4 14.5 1/7 twist Aimpoint ML2 Black Hill Blue box 77gr
Global Tactical Recon bbl Mk262, Federal GMM 77gr, BHBB 75gr, TAP 5.56 75gr All 4 loads will go sub MOA anyday. The Gold Metal Match has the tightest groups at around .7" at 100 yards
WOA 18" SPR barrel Mk262 1.65" at 200 yards
1:8 RRA 16in SS mid-length Hand-loaded 77gr Nosler < 1/2MOA
RRA Predator Pursuit Black Hills Red Box 77 grain HP, CorBon 69 grain HP, and Hornady 5.56mm 75 grain TAP All shot 1/2" groups at 100 yards
MSTN Recce Mod1 16" Lilja SS, Mid gas, 3 groove, 1:8 twist Mk262 Mod1 (Black Hills 5.56 77gr Seconds) 1/2 MOA
1:9 Bushmaster varminter, 24" barrel Winchester white box 45gr JHP Several 1/2 or less 3hot groups @ 100 yards
Stag 16in carbine Federal 50gr JHP sold @ Wal Mart Consistently less than 1 MOA
Bushmaster XM15 16", ACOG TA-33R-8 Federal Gold Medal Match, 69gr SMK 1.15"
RRA A4 Midlength, chrome lined, non free float on Stag Lower Black Hills Blue Box 52gr match 1/2" 5 shot group at 100 yards
RRA A4 Midlength, chrome lined, non free float on Stag Lower Black Hills Factory Seconds 75 gr Match 0.65" 5 shot group at 100 yards
Bushmaster 16inch Federal American Eagle 62gr FMJ 1" @ 100 yards

As you can see, there are a lot of different ammo types that people have good results with. To reiterate: To find the absolute best, you have to experiment to find out what works best for you. If you're a reloader, you should already know that. One additional note: While 1:9 barrels usually can shoot 75gr bullets, they're only marginally stable and you will probably find that they won't shoot very accurately out of these barrels.

Arfcom user Cody47 has done a great job shooting 5-shot groups of a bunch of different ammo and posted the results. This ought to give you some more data to ponder:
.223/5.56 Ammo Test Part1
.223/5.56 Ammo Test Part2