Good advice - seat them first then crimp them. I would hope that I should have thought of that,
I have some 260 grain .375 Accubonds , they are boat tails and have a cannelure. A good amount of neck tension combined with a crimp is essential; this will prevent the loaded rounds after slamming into the front of the magazine box being driven back into the case compressing the powder and possibly boosting pressures.
The nice hard white tip on the Accubond resists deformation from being slammed into the front of the magazine box. Hornady makes their .375 bullets with a tip that resists slamming - they might call it recoil protected or something like that.
An olde post but a good one (somebody must have dredged it up) for those with .375 H&H's and .375 Rugers and such. They shoot good with lots of H4350 and the 270 grain Hornady - a flat base bullet that can be easily seated first then crimped second. Not very much use for me but I did shoot a rock chuck (yellow bellied marmot or western variety of the eastern ground hog) with mine (.375-.338) - fun to shoot. Best use apparently is on big beasts like bears.