Mine is a standard freebore but I might throat it out 180-200 thou. I've been really happy with the velocity I'm getting with N570 but it's a super dirty powder and the loads are very compacted, so I might switch to N565/H1000/Retumbo…Retumbo I think would be perfect in this application since it has a similar burn rate to N570 but the same size kernel as H1000…There was a run of it the other day online but for the life of me I wasn't able to buy any. With N565 there's no compaction and w/ 98gr I can get 2730 but it's an absolute max load. 97gr is 2700fps and is better pressure wise. ES of both charge weights has been almost unbelievable at 2-3fps and preliminarily it seems really accurate. It also burns much cleaner and cleans up easier.
If I throat my barrel out to seat the 390gr out to where the boat tail junction is just above the neck shoulder junction I will probably be able to reduce pressure quite a bit, stuff a couple more grains of N565 in there, and get some more velocity…at least that's my hope cause 2850fps with the 390gr is pretty dang sweet.
H4350/RL16/SW Long/H4831sc might also work pretty well being able to seat the bullet out a lot further for the same reasons mentioned above. RL16 was a little slower than N565 during initial testing so I haven't really pursued it considering mine is a single shot on a short action and I'm seeking absolute maximum single shot performance. However from a hunting perspective, using powders w/ the H4350/4831 burn rate you can get a max charge in there and still load it to mag length, which is great! Even if you only have a MV of 2450fps, w/ the 390gr it will still be going 1600fps at 1000 yards w/ 2200ft/lbs of energy. If it expands like I hope, that would be perfect. At that velocity, recoil will be mild, and can be done in a much, much shorter barrel. Like I mentioned before, because of that I'm seriously considering building a rifle for that very purpose. To me a short, suppressed, 375 RUM would just be freaking awesome. I want to see what the on game performance with the 390gr is though before I fully go that route.
If I throat my barrel out to seat the 390gr out to where the boat tail junction is just above the neck shoulder junction I will probably be able to reduce pressure quite a bit, stuff a couple more grains of N565 in there, and get some more velocity…at least that's my hope cause 2850fps with the 390gr is pretty dang sweet.
H4350/RL16/SW Long/H4831sc might also work pretty well being able to seat the bullet out a lot further for the same reasons mentioned above. RL16 was a little slower than N565 during initial testing so I haven't really pursued it considering mine is a single shot on a short action and I'm seeking absolute maximum single shot performance. However from a hunting perspective, using powders w/ the H4350/4831 burn rate you can get a max charge in there and still load it to mag length, which is great! Even if you only have a MV of 2450fps, w/ the 390gr it will still be going 1600fps at 1000 yards w/ 2200ft/lbs of energy. If it expands like I hope, that would be perfect. At that velocity, recoil will be mild, and can be done in a much, much shorter barrel. Like I mentioned before, because of that I'm seriously considering building a rifle for that very purpose. To me a short, suppressed, 375 RUM would just be freaking awesome. I want to see what the on game performance with the 390gr is though before I fully go that route.
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