I have a VERY accurate 16" Bushmaster.  It's very finicky about it's ammo, but with the right stuff, it will really shoot.

My "open question" is this.
What barrels are you using, and what's the best accuracy you can get with it consistantly.  With what ammo?  Factory and handloaded?
I am spacifically looking for info on the super light ones.
I know that the heavy "Varmint" barrels shoot sub MOA, but what can be done with "standard" and light weight barrels?
So guys and gals..........what is Your input?

Hummmmmmmm

so far 49 people have viewed this post, and there have been no replys.....

Surely some of you folks have some shooting experience.  
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I've had good luck with my Bushmaster 16" Hbar V-Match.  Using  Sierra 69 gr BTHP Match Kings with 25.0 gr Varget.    The barrel was a 1-9 twist but I think it would have done even better with a 1-7 becasue of the heavy weight bullet.

Some of the guys that I use to shoot with that were into long range precision shooting used HBar Match SS barrels.   The stiffer the barrel the less barrel whip.

But............. I've changed barrels to an M4 14.5" with Phantom and lost interest in puching  holes in paper at long range and got into 3 gun matchs..

I have Olympic Arms SUM barrels in both 1:14 and 1:10 twist.  I shoot moly-coated 50 grain Speer TNTs and get great accuracy with both of them.  The 1:10 will shoot consistant, tight groups with either 50 or 55 grain bullets. (Berger or Sierra moly-coated)

The 1:14 twist seems to me much more forgiving with the thin-skined bullets like the TNTs.  Over the years I have used about 100 of the 1:14 twist SUM barrels for the guys that are shooting mostly prairie dogs at moderate range. (250-350 yards)  I've had a 1:14 as long as Oly has been making them, in fact, I was told that I got the very first barrel broached by Oly in the 1:14, and I still have it.

Neither of these barrels are real light, they are HMC contour, but not bull barrels.

Thanks Ramboski and DTech!.
My 16" bushmaster used to only hold about 2" with the best ammo, and 3-6 witha lot of other stuff.  I lapped the bore (it is chormes) and tried it again.  With 24.5gr. IMR 4895 and Sierra 69 gr match bullets it now holds 3/4" consistantly.  I have shot a few 1/2 groupes with it too.
I am going to make up an AR for a friends of mine in AZ.  She's a arther samll lady, and I'd like to make the carbine as light as possible, but without giving up enough accuracy for her to use it on small varmints at 200-300 yards.  That's the reason for the post in the first place.  I would love to mike it with a "super light" barrel, but I haven't heard any feed back on them.  If they will only hold 2 MOA, I will go to something hevier.  
She will be using handloaded ammo,  so we are looking for MOA if possible.
More input is better.

Anyone?

At that range do you all shoot free hand?  Once I get past 100 yds I use my Harris Bipod and weight doesn't matter then.  I don't have any feed back on light barrels.

I have an 18* stainless varmint barrel with 1:8 twist.  Limited experience shows 100 yd 5 shot groups between 5/8" and 3/4".  This is with a 53 grain Hornady flat base match bullet and 24.8 grains of 748.  I still have a lot of experimenting to do.