OK, Doctor's orders - use a full case of IMR 5010 and a magnum primer for a nice, easy shooting moderate speed load. WC872 can be substituted for IMR 5010. These are both surplus 50 BMG powders that get used a lot by the cast-a-holics on Shooters because they are cheap. These are mil-surp pull down powders that are bought in 4 jug case lots from Hi-Tech for about $7 a pound. These loads behind a 250 grain bullet do not kick any worse than a 30-06 does.
Use mil-surp IMR 7383 starting at 80% of case capacity to get a higher powered load. Work this up by normal reloading proceedures to whatever amount of recoil you and your gun can handle, all the way up to a full case if you can stand the kick and your stock doesn't split on you. This mil-surp "spotter powder" runs between IMR 4064 and IMR 4831 in speed, so if you want a "safe" commercial powder to work up a similar load with then use IMR 4831.
This brings up a point, IMR 7383 looks to be a good cheap jacketed bullet powder. It has been successfully used in a broad range of jacketed bullet rounds now. It becomes more consistent the higher you run it up in its pressure range. Like most pull-down surplus powders, it behaves slightly differently in small cases vs big cases but can be characterized as being slightly faster than IMR 4831 and slightly slower than IMR 4064.
Understand if people are talking IMR 7383 loads at you and you don't have any you can drop in the commercial IMR 7831 powder because it is slower.
YOU CAN"T DO THIS BACKWARDS, you can't drop IMR 7383 powder into loads designed for commercial IMR 7831 powder because the pull-down IMR 7383 stuff is slightly faster than commercial IMR 7831 and you will overexpand your case heads (damage your brass) and likely blow out a primer.
IMR 4064 (safe starting loads) --- IMR 7383 ---- IMR 7831 (don't use these load weights, too much pressure)
So, I hope this is moderately helpful for you. If you only use canister powders and still want to bruse your shoulder good with a 8mm 250 grain heavy bullet, just stick with IMR 7831 powder for your heavy loads and you will still be fairly safe. Just start out with 80% case capacity loads and work up until you begin to lose good accuracy (BTW it's your flinch, mostly).
The 8mm Max will strip some on the long land rider nose with the heaviest loads but it has caught up with itself by the time the main driver bands engage and engrave, so there is no gas leakage noted even on the nastiest loads. Leading has never been an issue with the bullets, no matter how agressively they are driven.
Once you shoot a few hundred of these babies you will find 30-06 and 7 mags are just mild, fun shooting guns. Your flinch with these milder guns will totally disappear as your body knows what real recoil feels like now.
Now take these heavier powder loads and push a slightly lighter 8mm Karabiner bullet at a deer with them. Want to talk about a large wound channel pushed all the way through an animal?
The 8mm Karabiner, she will do it. She is equipped with the nastiest fast moving lead rifle bullet meplat known to man.
Oldfeller
