I did not want to hijack Sonny Burnett's thread but I have a question about twist rate.

SeafireB17G posted that his 1-9 can stabilize 77 and 80 grain bullets. Those two bullets are quite different in length as the 77 can be loaded to mag length.

Conventional wisdom has been 1-7 to 1-8 twist in AR service rifles.

Does adding 6-8" of barrel length compensate for less twist rate? or is 1-9 all that is really needed?

If you want to use the heavy bullets, I'd go at least 1-8. The slower twist may work, but not likely. Picking up velocity will change things as the rotational speed (rpm) goes up. That is why you can use a 1-14 twist on a .220 Swift, it will stabilize heavier bullets than .223 velocities.

1in9 is good IF you have enough velocity ...... I was unable to get 70 gr TSX bullets to stabilize in 2 different 1 in 9 twist barrels . one that had 20" of actual barrel length a Rem 700 VTR and one a 24" barrel CZ527 Varmint ... Velocity was around 3000 fps.possibly 2900 fps in the 24" barrel as it was pretty cold when I shot those loads .. They made nice oval holes thru the target ..... The cz shot them much more accurately than the vtr did .. About a 2" group @ 100 yrds as opposed to about an 8" pattern with the vtr ......But the bullet holes thru the target were the same for both rifles ....

1/7 or 1/8 is good to go. I shoot 55gr and up. 1/9 is an ify situation w. the heavier bullets. Some barrels will do well while others do not.

Go 1:7. Adding barrel length will not compensate for slower twist.

My 223 Service and Match Highpower rifles sport either 1-7.7 or 1-8 in barrels. They shoot the 77 and 80 grain SMK's great. No problems there.

I keep reading where some people can shoot the 80's in a 223 with 1 in 9 and other cannot.

As stated above it seems as though it possibly could be a function of velocity. Longer barrel bolt guns should generate generate more velocity than a service rifle.

My Savage 10FLP .223 with 24" barrel will shoot 75gr bullets quite well. I used to shoot a model 12VLP with a 26" barrel and it was only slightly faster with the same round. Seeing that others are able to shoot a 77gr bullet makes me want to test that in my rifle.