I have to agree on some loads shooting very well at 100 and not shooting at 300 or so. I believe this to be the bulllet design. Generally, if you are shooting those type of groups at 100 it should do much better than 6" at 300. Generally, 1/2 at 100= 1" at 200 and 2" at 300.
What power scope to you have, what type of rest are you using, and what type of target are you shooting at? This will give me some idea of where to go on this for an answer.
I have seen 40gr bullets shoot very well at 500 yds as well as the heavy ones.
