338 SIN Testing
The other thread was getting so long I thought I would start another and list my data as I shot it. Had a great shoot this morning with the 225 grain cutting edge bullet .640 bc. Best accuracy out of my 24" barrel seems to be between 3100-3150 fps. I had one hole 100 yard groups in this velocity range with four different powders. Magpro, Winchester WMR, IMR 4831 and RE-19. From my limited testing so far it seems this cartridge is going to be very easy to load for. About anything shoots well in it. When I got near 3200 fps the groups began to spread so I backed off and started fine tuning in the accuracy range.
So far the most accurate loads are 95.5 grains Magpro, 93 grains winchester wmr, 87 grains imr 4831 and 86 grains RE-19. 4831 and re-19 retained the best accuracy at the highest velocities around 3170 fps. I expected that the faster burn powders would turn out best in my short barrel. The beauty of this efficient design is that it does very well in short barrels with faster burning powder than most big magnums. By utilizing the faster powders excellent velocities and accuracy can be had with a short barrel. This allows short barrel light carry rifles that can achieve great accuracy since there is no fireball of turbulence when the bullet exits the barrel as experienced with the RUM and larger class 338's in short barrel versions.
My rifle weighs just over six pounds so I stopped testing the 300 SMK in it. I shot a few and it was brutal. Winchester WMR shot great with the 300 smk but I stopped at a little over 2700 fps because of the massive recoil. I could have gone well into the 2700's which I thought was very good considering the 24" tube. My 340 wby shoots the 300 SMK 2730 fps and my two 338-300 RUM's shoot 2830-2850 fps all with 28" barrels. Basically there is 120 fps difference on average between the 340 wby and 338-300 RUM. The 338 SIN powder capacity is exactly half way between these two so it figures to hit right in there. With a 28-30 inch barrel I think 2800 fps is possible with less powder than the RUM's plus fit on any standard magnum action without modifications. This with plenty of room to load the 300's out to the lands since the case is about the same length as a 338 winchester.
Because of recoil in my light rifle I am only going to test bullets 225 grains and lighter in this gun. When Devin first showed me the diagram of this cartridge I immediately thought it was the answer to a light carry rifle for long range at large big game. I saw the extremely efficient design and so far it has done everything I thought it would. A 225 grain bullet with a .640 bc at 3170 fps out of a 24" barrel that weighs just over six pounds is my answer to long range backpack style hunting. I am going to test some 185 and 200 grain bullets over the next couple days but I expect to end up with the high bc of the cutting edge bullet. I am going to load the 4831 and Re-19 loads now and stretch the range out some this evening. I seated the bullets like recommended by CE and have no reason to change that right now with one hole groups at 100 yards with these two loads. If the accuracy is good at long range and the bc tests out to be around .64 then I plan on trying this combination in Alaska in August.
I will report back in as I get more data.
Predictions are difficult, especially when they involve the future
Last edited by Long Time Long Ranger; 06-22-2011 at 02:02 PM.