AR Carbine Barrel Twist Rates affect what bullets you buy

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I was at a store the other day and spied good prices for 45 grain FMJ .223 bullets so I checked out the optimal twist rates and bullets for my Colt 1/7 twist rate barrel. Most barrels for the AR type have been sold as 1/9 twist rates thus the range of bullet weights are 45 to 75 grains. The 45 grain heads will work here for 1/9 twist.  My barrel has a 1/7 twist rate and the range of bullet weights are 55 to 85 grains. So the 45 grain heads would have been a poor purchase. My barrel is more in keeping with a dual purpose hunting and tactical weights.

It is best as a deer hunter to hand-load small quantities of these heavier heads/powders to see what works best. I would then chronograph them and determine lethal energy needed on deer at ranges. So I will do that this spring in an article. Proper spin of the bullet includes enough velocity too for gyroscopic stability. JBM Ballistics has a calculator for bullet stability

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi 

Web research shows that the Hornady 80 grain A-max is a great stable bullet for my 1/7 twist rate. But use the calculator!!

Good Shooting!

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About Ed Hale

I am an avid hunter with rifle and Bow and have been hunting for more than 50 years. I have taken big game such as whitetail deer, red deer, elk, Moose and African Plains game such as Kudu, Gemsbok, Springbok, Blesbok, and Impala and wrote an ebook entitled African Safari -Rifle and Bow and Arrow on how to prepare for a first safari. Ed is a serious cartridge reloader and ballistics student. He has earned two degrees in science and has written hundreds of outdoor article on hunting with both bow and rifle.