Hello all,

Seeking AR builder's opinions:

First time builder here. Looking to build a bench only tack driver based on a Mega Heavy Duty upper. I am considering a 1/12 twist for 40-50 gr rounds. Since I am limiting this gun to paper only, would you go with a light grain/high velocity setup like this, or would you stick wit the faster twists and more versatility.

Thanks

Faster twist with lighter bullets is a no-no in the 223 platform.  My heavy barrel is 1;9 as I shoot only 50-68 grains in it.  Actually changing from 68 BTHP  w/Varget to 52 BTHP with TAC.

First, no don't build a 1:12 .223 gun. 

Second, if you want to build a .223 for accuracy, it usually means you want to shoot heavier rounds, not lighter. Heavier round mean higher BCs, which means less wind drift over distance. If you are reloading for volume, yeah the light varmint bullets are cheap. However, if you aren't, they aren't so easy to find commercially.  77gr SMK/nosler based rounds cna be had regularly, and sometimes at pretty good price per round for accurate ammo. 

I personally like 1:8 barrels, it covers pretty much every useful bullet for .223/5.56

Excellent info. Thank you. Looks like 1:8 is the most logical.

I am looking at a Douglas in this twist 20"

Factory recommended ammo for my Savage 10FCP-K (bolt gun) with 24" 1:9 .223Rem barrel is 69 grain Federal Gold Medal Match SMK BTHP (GM223M).  Despite what all the charts say about twist vs grain, the gun does like em plenty.  I've shot 75gr match ammo through it as well, and it liked that too.

Back when I got the gun, I didn't do enough homework on twist rates, and when I researched further well after getting the rifle, I was disappointed Savage went with 1:9.  For a bolt rifle that is supposed to be very accurate, it doesn't make much sense why they chose a 1:9 when a 1:8 or 1:7 would have made much more sense for the most common match ammos out there IMO.  However, in practice, with good, high quality ammo, it has not seemed to make a difference, or at least a substantial enough difference that it shows with my shooting skill level.

My ARs have 1:7 and 1:8 barrels, though I don't shoot much high end ammo through them.  If I were starting fresh with any .223 gun, I'd probably try for 1:8 for the most versatility.

My AR is a 20" 1:9 chrome lined. I typically shoot 55gr, so I can't speak to heavier rounds, but I will say it's much more accurate than I am. I'd wager that depending on the level of competition you're doing, the build you're looking at will suffice. It's easy to go down a rabbit hole and just spend tons of money, but you eventually reach a point of diminishing returns. I'd think that loading your own ammo, and experimenting with what loads the particular rifle does best with will yield greater results in the long run

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Excellent info. Thank you. Looks like 1:8 is the most logical.
I am looking at a Douglas in this twist 20"

For the longest time, 1:8" wasn't that popular. People would pick 1:7" or 1:9". My Spikes upper, which they installed an AA piston kit, is 1:8"... and I haven't found a load it hasn't liked (had function issues with UMC .223... but was the buffer combination I was using; ran fine with a standard buffer).

My FDE build was based off an 18" 1:8" barrel.

If you want to hunt groundhogs, yea 1:12 works.   Heavy slugs lack rapid expansion needed for soft targets. Been there tried that,  prefer to shoot .223 with 50gr TNT's or 55vmax, my 1:12 barreled .223's are more accurate then the 1:9 ones I have with those slugs. Will the heavies shoot accurately, yup but terminal performance is lacking.  Think big exit hole, do you get more then 300yds hunting in NJ ?

side note,  we shot 500yds with 55r fmj in 1:12 colt m16's back when I was a Marine, no problem

your results may vary