Best .223 or 5.56 choices for 1:9 twist rate

[Falcon78]

Just wanted to hear your opinions on which weights/loads perform well for a barrel with a 1:9 twist. The general consensus seems to be that you can use "up to" 69 grains with a 1:9 barrel, but does anyone have experience at over 100yd ranges where heavier rounds out a 1:9 might begin to keyhole? Since 69 grains seems to be the upper limit, I was wondering if 62-65 grain rounds actually perform better for this twist, or if the 69 gr. rounds match the long-distance performance of the lighter rounds in a 1:9 barrel (barrel is 20").

For the Saiga experts out there, can you tell me if you use 5.56 or 223 - which provides better accuracy given the unclear nature of the exact chamber size and what weights you have tried that seem to work well. Thanks for your input.

 

[Falcon78]

I found this page as well, which states up to 73gr, but of course acceptable performance is different that optimal performance.

 

[LTR shooter]

In my 20" 1 in 9" twist bolt gun the 69 MatchKing has performed remarkably well. The next lightest I have tried has been 55 Bergers which also highly accurate. The 62 or 65 bullets should shoot well too.

 

[Eb1]

I am finding that with my 1:9 AR-15 the 69 gr Sierra Match King is very, very accurate, and moving at 2864 fps.

The same AR-15 loves 55 grain Black Hills Soft Points. It has the same accuracy as the 69 grain Sierra Bullets, but not POI.

I have tried the 75 grain A-MAX in this 1:9 twist AR-15. I believe that the bullet length is 1.13". Looking at a twist calculator it calls for a 1:8 twist minimum despite the box saying 1:9 for these bullets. My gun will not shoot the A-MAX.
Now here is where it becomes interesting, and I am starting to believe that bullet length is more relevant to accuracy then weight. At least in my tests. Because the 75 grain Hornady HPBT is .985" (avg) in length. Looking at the twist calculator it is calling for a 1:9.5 twist for 2700+ fps with a bullet of this length and caliber.

I am going to shoot these bullets this weekend. I have a hunch that they might just prove to be accurate in my rifle. At least I am hoping so.

I will keep you guys informed of my findings. So to the OP, I would think the 69 grain SMK will be good for you. It is a very nice and accurate bullet. Look up some information about BC and twist rates. Maybe you will conclude the same findings as I did through you own tests and investigations.

 

[Falcon78]

Cool, thanks for the input. I would definitely like to hear how they work out for you Eb1.

 

[Falcon78]

Shameless bump... I know I'm not the only one out there with a 1:9 barrel

 

[Falcon78]

One more thing, I'm not sure which loads tend to be more accurate out of the Saiga, .223 or 5.56. (the answer is probably 5.56 but I'd be happy to hear others' results)

And does anyone have any long-distance range results, as far as different weights? Thanks.