I pulled out one of my 338-300 RUM's to test some loads with the 225 Cutting Edge bullet. It is a 28" Hart barrel 1-10 twist. This is one of my throat designs from the early development of the cartridge in the late 90's using a partial wby freebore. So many throats have been done by so many smiths later on as the cartridge gathered a closet full of names the data may or may not be useful in your particular rifle but will give you a good idea. This rifle shot very well at 4.06 coal. My old accuracy load of 102.5 grains of RE-25 shot .36" at 100 yards. velocity was 3312 fps average. My old accuracy load of 100.5 grains of WMR shot .52" at 3286 fps. Fed 215 match primers with all loads. These bullets are extremely long and are recomended seating very shallow into the case therefore the long coal. They are nearly as long as the 300 smk. I will get a bullet length later to give you an idea. I tried seating them deeper to gain the success I had with the 338-378 wby test but they did not do well in this rifle. It preffered the seal tite band outside the case mouth. These velocities combined with the .64 bc makes this bullet a good alternative for a lighter recoiling rifle out to 1000 or so yards. I will test it with some more powders later on.