Originally Posted by Jammer1
I am seriously considering a 6 x 45 for coyote hunting. Here in Western Ok, the wind is ALWAYS blowing and the 223 is the functional equivalent of a ping pong ball past 250 yards. I have plenty of larger calibers and I think the 6 x 45 would fill the gap nicely. Its easy to load too.
The 6x45 can shoot low drag bullets very well from a short action bolt action with a 2.8" magazine, but in an AR-15 the magazine limits bullet choices. Before you select the 6x45 you might want to consider other 6mm choices. .243" bullets with the same BC at the same muzzle velocity have the same wind deflection as .224" (or other diameter) bullets. To get better wind deflection you either need a higher BC or higher velocity. Compare them with a ballistics calculator if both the BC and velocity aren't equal or higher. Bullet weight is not an indicator of wind performance.
Here are three 6mm cartridges which have available AR-15 barrels and/or uppers. The numbers are case length and case capacity.
6x45 = 1.759" 31.5 grain
6PPC = 1.505" 32 grain similar performance to a 6x45 in a 2.8" magazine.
243 WSSM = 1.663" 53.9 grain similar performance to a 243 Win in a 2.8" magazine.
The 6PPC and 243 WSSM are available in factory uppers from Model 1 Sales and Olympic Arms.
Either can give more downrange energy and less wind deflection than the 6x45 from an AR-15.
AR Stoner (midwayusa) offers a 6x45 AR-15 barrel. Also a 243 Win barrel for a DPMS LR-243.