I'm new to these ARs and I'm getting ready to make my first purchase. I'm looking to get something with a varmint upper since primary use will be paper punching and coyotes. I think I would like to get an 18" bull barrel rather than a 20" to try to save a little weight while carrying in the woods. Is there any measureable difference in accuracy between the 2 lengths?? I know tht there will probably be about 100 fps velocity difference, but since I handload, I can possibly compensate some by using apowder on the faster end of the scale. I also have a question on twist. I've researched this  also and I think I would be better off with 1 in 9 twist. This would allow me to shoot some of the 53-55 gr bullets for varmints. My question is what is the heaviest bullet tht twist will shoot accurately??  Thanks for any input.

bowhuntr

Accuracy difference should be negligable.

1/9 can handle 69gr easily.  Some people say they've had good luck with 75 or 77gr while others haven't.

Agreed on negligible accuracy difference.

So far as bullet weight, 55-75 grn with 69grn being about ideal for max accuracy.

If you plan on carrying it I would not recommend a bull barrel. I had a 16" bull and thought it would be handy. It was just too heavy to carry and especially for off-hand shots it was impossible. I went to a 16 inch HBAR(I could probably go lighter) with great success. I get sub MOA groups with bullets ranging from 45 gr to 68 gr (I wouldn't go higher than 69-70).

I think your choice of an 18 inch barrel is very good. When I shoot out my 16 or get bored I'm going to get an 18 (low profile like .75 from reciever to muzzle).

If it's a bench gun the Bull barrel is fine, but if you want to pack it, get a lighter barrel. I will bet you won't notice any accuracy difference unless you are shooting many rounds at a time and still it will be minimal.

[img]http://www.hunt101.com/img/047933.jpg[/img]

5 shot 100yd group using 68gr hornady bthp, bipod and wooden bench.
[img]http://www.hunt101.com/img/040107.jpg[/img]