I'm in the midst of acquiring the parts needed for building my first ever AR and i'm most confused by what i should select for the barrel. I want to build a target only gun (not defence or hunting) that i shoot from the bench at the rifle range for long range paper punching and plinking. I want a reasonable level of accuracy, but i don't reload and don't want to buy premium ammo all the time. I was thinking a 20 or 24" full floated HBAR or varmint barrel but not sure if those will shoot the cheaper stuff with respect the the target oriented twist rates and cheap bulk bullet weights. Is there a configuration that will shoot the cheaper ammo with some level of accuracy and also be compatible to shoot the match ammo just as well or better? I just don't know which rates are suited to which bullets but understand that its an important factor, no?

a 1x9 twist barrel will do 50 to 62 gr accurately. If you want long range target you need heavier bullets and should go with a 1x7 twist barrel. if you are staying on a bench go for the 24. But what do you consider long range? I get good accuracy with Fed 55gr out of a 1x9 twist at 200yds. When I think of long range it starts @ 500.

Well, long range for me is the 200 yd range at Ft Dix. Thats all i really have at my immediate disposal right now. is the 24" is overkill for this range? What barrel length/profile are you using?

That is where I shoot. I have a stadard 20 inch A2 rifle. The one I am building will be a 16 heavy barrel with 1x9 twist. If weight is not an issue go for the 24, it is not overkill. If you plan on going longer ranges , definately get the 24 for the added velocity.

1/8 or 1/9 would work well with 55 grn.

 

Id stick to stainless steel bull barrel for your app. Fluted or not, your choice. Fluting lightens up the barrel, and arguably adds surface area to disperse heat quicker.

 

The length of the barrel, Id go with 16-20, probably due to the weight of the thing. Remember the shorter the barrel the less velocity, but will Not impact accuracy.

 

Best of luck to you!

So the 55-62 grain are good for 1-9 and 1-8 twist, but what are the "heavy" grains to use in the 1-7?

Yes, heavy bullets go with 1x7. The need the faster twist rate to stabilize them in flight.

Read this.

 

http://ammo.ar15.com/ammo/

I might be way off base here, but a 1/8 or 1/7 will handle 55 grains very nicely and give you the benefit of the heavier loads. I don't buy that a 1/8 or 1/7 won't shoot 55's accurately.