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My 18" 1:8 heavy DMR barrel shoots 75 and 77 grain match loads very accurately at 500 yards, and my 16" 1:8 medium contour Carbine barrel shoots 55 grain remanufactured soft points into a 1/4" cloverleaf at 25 yards. Neither barrel seems to be bullet weight sensitive, shooting everything from 45 grain A-Max bullets to 77 grain Matchkings with aplomb. Sure, the match bullets shoot the best in both barrels, but all of them are well within the range of acceptability for what is essentially a general purpose gun.

Bitter Clinger wrote:

locke_n_load wrote:

hounddog wrote:I'd like to ask a quick question if you all don't mind? I'm not real saavy on barrel twist rates. For a 5.56 barrel of 16" length, what do you think is the best twist rate? I've heard some are better for different things and I see they offer 1-7, 1-8, and 1-9. Excuse the limited knowledge I have on this please. I'm more familiar with pistols.

Stay away from 1-9 if you can, as it will not stabilize heavy bullets, if you ever plan on shooting any. 1-7 is most common after that, and then 1-8 is somewhat rare, but both should be fine. If you plan on shooting very light bullets (<50 gr) and very heavy bullets (>65 gr), go with a 1-8.
But if all your shooting is 55-62 gr (most common ammo), either of the 3 will work for your purposes, but I personally go for 1-7.

http://texaschlforum.com/viewtopic.php? ... e&start=15

Yep. My last two builds have been on 1:8 barrels.

Another hint.... Generally speaking, comparing any two barrels of equal length in which one has standard rifling and the other has some form of polygonal rifling, the polygonal rifling will tend to produce slightly higher velocities without negatively affecting accuracy. Just like other smaller calibers, .223/5.56 bullets tend to rely on high velocity for wounding potential, particularly with ball Ammo, and carbine length barrels produce lower velocities than than mid or rifle length barrels. Polygonal rifled barrels tend to cost more than their standard rifled counterparts, but not necessarily tons more. In my opinion, it is well worth the bump in cost for a polygonal rifled barrel, especially for a carbine or SBR length barrel, to bump up muzzle velocities without raising chamber pressures. And, there is an additional benefit, and that is that polygonal rifling is MUCH easier to clean, as anybody who owns both a Glock and a 1911 can tell you.