I have a new DTA 338 LM with a 18" barrel. I have been working up a hunting load for it and have observed something I dont understand. I am loading 280 grain Barnes LRX bullets for hunting elk. I chose a starter load of 91.5 grains of RETUMBO. I had very good accuracy but mild pressure signs. Being stubborn and wanting all the velocity I could milk out an 18" barrel, I tested it out to 840 yards. I got consistent 5" groups with 20.5 MOA. After a few particularly sticky bolts, I decided I had better back off of the 91.5 load. I began down at 86 grains and ladder tested up to pressure signs at 91. I settled on 89.5 grains of retumbo. The interesting thing is my MOA for 840 yards is .25 MOA less than the hotter 91.5 load. velocities were similar too (2610 average for 89.5 and 2618 for the 91.5). Extreme spread was much tighter for the 89.5 load.
My thought on why the two loads performed similarly is because of incomplete powder burn in the short barrel. Only so much powder is being burned to propel the bullet faster before it exits the barrel. I really have no idea though.
My thought on why the two loads performed similarly is because of incomplete powder burn in the short barrel. Only so much powder is being burned to propel the bullet faster before it exits the barrel. I really have no idea though.
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