1:7 vs. 1:9 best compromise bullet gr.

[shooting4pizza]

I have an Arsenal AK in .223 / 556 with a 1:7 twist barrel and a Rock River AR-15 Entry Tactical with 16” barrel with a 1:9 twist barrel. I have read a number of articles on 1:7 vs. 1:9 twist rates and the best bullet gr. weights for accuracy and bullet stability.

I would like to inventory one gr. weight. I have started to accumulate ammo in 62 gr. as a “best of both worlds” approach to accuracy and functionality.

Anyone have any ideas or opinions on this?

 

[JImbothefiveth]

I think there were some issues with 62 grains stopping power, although I could be thinking of an entirely different issue.

Oh, and welcome to THR.

 

[RyanM]

62 gr all lead bullets will probably end up just a little bit overstabilized in 1:7, which can mess up accuracy a bit. Probably best to err towards best accuracy in the AR-15 though, which you'd be doing with 62 gr bullets. The military 62 gr bullets are somewhat long since the core is part steel. Dependent on the specific bullet shape; I'd guess that 62 gr open tip boat-tails would be just fine in both, while FMJs would be a tiny bit overstabilized from the AK, though that probably wouldn't open up the groups more than 1/2 MOA.

You may want to research what it'd cost to get a 1:7 on your RRA, though (and you'd probably have no trouble selling your current upper to fund it). 75 gr ammo is supposed to pack quite a bit more punch than lighter weight bullets. There's a guy on AR15.com who's cleanly killed some decent-sized boars (200-250 pounds and up, I think) with Prvi Partizan 75 gr OTM.

 

[Winston_Smith]

My understanding is that the 62 grain will be fine for both. 62 gr is about the max for 1:9 and 55 gr is no good in a 1:7.

 

[lead-inspector]

Try this link. there is a wealth of information.

http://razoreye.net/mirror/ammo-oracle/AR15_com_Ammo_Oracle_Mirror.htm

Steve

PS I would stock up with M193 (55gr) it will shoot well from both rifles