A friend wants to get his feet wet with longer range shooting. He has a Colt LE6920 AR.

Twist is 1 in 7". Assuming we use the heaviest bullet that barrel will stabilize and work up a decent load, what kind of accuracy should we reasonably expect to see?

how good are you as shooters? that's the most importante question

a friend of mine was able to get less than 1/2 MOA (target was at 300m) with his colt 16'' 1/7 barrel using reloaded ammo, quality scope, FF handguards, quality trigger and a good trigger finger

Colt make good barrels

Damn that's about the best shooting carbine I've ever heard of.

My 6920's shoot about 2 MOA

The honest expectation of a box stock 6920 is to take it, some 1.5MOA ammunition, and be able to shoot consistent 2MOA groups from a rest, and solid sub-4MOA groupings in real world shooting.
Most folks can take a 6920 with aftermarket trigger and match ammunition and make 2MOA groups from a bench, which really is more than necessary in the accuracy department.

We had a couple of 6920's out at the range this last weekend, and the  best groups were around 1.5 moa.  This was with 75gr handloads and a Leupold 1.5-5 MRT-DDlite ff rail. The other one shot around 2-2.5moa with the same load, but it was topped with the Leupold 3-9x "AR-15" China scope.
Colt sometimes makes really accurate barrels, but it's kind of hit and miss––and they don't seem to care, as long as they shoot "mil-spec" moa, whatever that really is.  1.5" groups and 300 yrds seems ...questionable.  The 6920 is a great gun, and replacement match barrels are cheap compared to the rest of the gun, so...why not?

same for me.. about 1.5-2 MOA from both my 6601 and 6731

btw, pics of the "monster"

EDT: taken back, not worth it.

Damn that's a good shooting 6920!!

While I don't know him personally, most people on here seem to respect this guy's opinion.  His accuracy write up below is for a 6520 16" lightweight barrel.  I would expect a 6920 16" M4 barrel to shoot at least as good.

Molon Link

Edited to add that he free floated the barrel and used a 25x scope and match-grade handloads and he appears to be an extremely experienced shooter.