from my experience with boat tailed bullets, i find that they are more difficult to "tune in" that standard flat base bullets. the first thing i would check is the muzzle crown. ANY damage there, and boat tail will be thrown off course 10 times as bad as a flat base. look at it with a STRONG magnifying glass, or eye loupe. my 300 win mag, which likes most of its ammo on the high speed end, only likes Hornady 180g btsp's down near the starting end. and with one 165 grain boat tail, i have to go below starting load to get satisfactory results. every rifle likes something different. i tell my brother that given any bullet, powder combination, i can find a decent load for it. it may not be top speed, or it may be pushing it to the limit, but with trial and error, you can certainly find a satisfactory load. at least if satisfactory does not mean 1/2 moa or better. for a hunting rifle, for me that means less than 2" @ 100 yards. my reasoning for that is because none of us are anywhere near as steady as a rest is, so we have to leave "wobble room" for us!