I just had the the chance to run my Cooper through the chrony. The rifle is a model 52, 24" barrel, chambered in 6.5x284 Norma. I have shot this rig out to 1,000yds. The one thing I now know, there is quite the difference from 500yds to 1,000. Anyway, the load I chronograph-ed was 140grn Berger vld's, 51grns 4831sc and a base to ogive of 2.380, which is approximately .01 off the lands. I was hoping the fps would be around 2,850. The five shots were, 2,996 / 2,926/ 2,969/ 2,965/ 2,943, for an average of 2,959. From what I've read, the sweet spot for this cartridge is 2,950, for what it's worth, that also seems to hold true for this rifle as well. Enjoy the outdoors!
I think you need to check your chronograph. Your come up from 500 to 1000 yards is consistent with several 6,5-284 rifles that I have tested with the same 51 gr load of H4831sc load that ran velocities at 2700-2800 FPS. The come up for a velocity of 2960FPS at 1000 ft alt and 50 degrees would be approximately 18 MOA. Your come up of 21 MOA would put you in the 2700-2800 FPS range which is consistent with your load and barrel length. My Cooper 52 with a 26" barrel with 53 gr of H4831sc runs 2950 FPS and has a come up of 17.5 MOA. My Savage with the same load and 24" barrel ihas a come up of 18 MOA. All this assumes that your scope tracks true, and there is no radical difference in your lot of 4831sc. IMHO.
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