Wade, another couple of things to consider although you have probably already thought of them:

1. When shooting from sandbags, no part of the rifle should touch the bag. Your front hand may rest on a bag, however.

2. If your rifle has a splinter forearm (very likely), you do not actually grip the forearm. The forearm is to fill your palm, but you actually grip around the forearm so that your fingers come up onto the barrels.

3. The 2150 fps standard velocity for the 450 NE, 470 NE, 500 NE was out of 30" barrels at the proof house. Lop off 6" and lose 100 fps.

4. You might want to try other brands of bullets because they may regulate differently.