This topic is of interest to me, because I'm working up some loads in my .338 RUM, and the velocity I'd expect just isn't there with WC872. I've put 103 grains of WC872 behind a 225 grain Hornady bullet, lit it off with a CCI 250 primer and I only get 2651 fps! This is in a Remington 26" factory barrel with a vais brake. The 103 grains is getting close to a compressed load. I have to shake it down pretty good to get it to the bottom of the neck.
Using 95 grains of WC852(s) with the same setup I get 3165 fps. No pressure signs with either load. What gives? Any ideas?
You are just running a powder with a pressure/burn rate more suitable to your rifle. Ths 872 was simply too slow for your bullet weight and bore length. If you were to switch to 300grMK, you would find the 872 to be a better powder.
That is why we test loads. You never what will be the magic combo. Going to do the same with my Mystic. Been using H4831SC which should be a great powder. However, vel and accuracy are not what it should be. Going to try H4350 to see if I can improve the performance.
It depends. How are the CCI BR2 doing? Are you getting good velocity and low or consistent ES's? Is the accuracy you want there? If your current load is meeting all you expectations then I'd make it my "go-to" load for whatever you need it for.
On the other hand, try the mag primers and see what you can do with it. I've had some rifle/loads I couldn't get to perform like I really thought they should. One in particular was a heavy barreled .243 shooting the 87gn V-Max and H414. Swapped out the BR2 for 9.5M and voila. Same with a 700VS I had in .22-250. I used 9.5M behind 34.0gn of Varget and the 40gn NBT. Both of these loads went from 3/4 to sub 1/2".
I'm not saying a magnum primer is the cure-all, but it doesn't hurt to try different things. Don't forget to start low and work up. JohnnyK.