I am looking to get a 16 inch lightweight upper that I would primarily use for .22 but would want to use it for .223 sometimes.
Is there an ideal twist for both? I have never paid any attention to twist rate before. I don't even know what I have now.
Thanks
Chip

1/12 works great for both. I believe most .22LRs have a 1/14 twist so 1/12 is close.

The only drawback is you'd have to shoot 55gr or less with .223.

Now the question is, can you get a 16" 1/12 barrel? I used a 20" M16A1 barrel for mine. Maybe you could cut one down.

The bore diameter of the 22LR and 223 barrels are slightly different.   Also, 22LR barrels twist rates are usually 1/16 while the 223 barrels are 1/7 or 1/9.  You have a few choices, but they are going to cost a bit.  Surplus A1 1/12 barrels cost about $100-150 depending on condition.  You won't get match accuracy, but it will work for both 22 and 223.  

You can get the 1/12 barrel and have it cut and threaded to 16".  The gas port will have to be plugged and the new one drilled.  The front sight base will have to be moved.  

I have an A1 barrel that was cut down to 11.5 and had a 5" flash hider permanently attached.   I only wanted to shoot 22lr out of it so I didn't have the gas port drilled. For less than $100,  KKF cut the barrel, threaded and recrowned it, and installed the FSB on it.  I already had the barrel and wasn't going to use it, so that didn't cost me much.  For the total value of the barrel and work, I guess I could have just bought a 22lr barrel and had it profiled to what I wanted.  Oh well.

Or you can contact someone like AR15Barrels.com and have them cut and thread a 1/12 barrel to 16".  They can contour it to a light weight and have them install the gas port and FSB.

For the cost of the kit ($100-150), barrel+parts($125-200), and labor($100-200), you might just consider buying a 22LR upper from DPMS/Bushmaster, or settle for mediocre performance out of a 16" 223 barrel with a 1/9" twist.

Quoted: 1/12 works great for both. I believe most .22LRs have a 1/14 twist so 1/12 is close. The only drawback is you'd have to shoot 55gr or less with .223. Now the question is, can you get a 16" 1/12 barrel? I used a 20" M16A1 barrel for mine. Maybe you could cut one down.

I believe there might be some 1/14" barrels around (EMCO?), but they are scarce.


ETA, here is a KKF modified 11.5" barrel, SP1 (1/12").  You could perm attach a 5" flash hider.
www.ar15.com/forums/topic.html?b=7&f=119&t=297129

I picked up a SP1 1in 12 twist upper and then later on a M261 kit with extra mags inserts all in for about $300, it makes a useable plinker for both calibers but not accurate enough for much other serious shooting.  The only advantage with that setup is you can carry the 223 bolt ass. and mags and swap it out without a trip back to the truck or home.


For the money you can buy a pretty decent and accurate 22 rilfe a like 10/22,

Standard twist for .22LR is 1/16.

Standard twist for non-AR .223s is 1/12.  Standard twist for most ARs is 1/9, but 1/7 or 1/8 is also very common, and 1/12 on some barrels.  And anything from about 1/6 to 1/14 is available in custom barrels.

The original AR15/M16s had 1/14 twists, but they were borderline in cold, thick air so production ones had 1/12 until the A2 in the early 80s when they went to 1/7 on the M16s and most civilian ARs became 1/9.  "Ideal" twist depends on what weight range of bullets you want to shoot.  If what you have now is a Colt there's about a 50% chance it's 1/7 and 50% that it's 1/9.  If it's any other brand I'd say 95% chance that it's 1/9.

To get really good accuracy with the .22LR you need a dedicated barrel that's 1/16 twist and the proper bore diameter, which preclude shooting .223s out of it.  Most people report better accuracy with .22LR kits in 1/12 barrels than in the 1/9 or 1/7 barrels so if you have to be able to shoot .223s out of the same barrel then your best bet is to find a 1/12 such as an old A1 or SP1, but they're hard to find in 16".  Also, be warned that if you shoot enough .22LR between shooting .223s it might not cycle the .223s because of the gas port plugging up.  

Thanks guys. I'll probably just leave it as is.