375 H&H issues?

[375 Ruger Fan]

Is one of the issues that I am having is the barrel twist rate of 1:10.5? I thought the gunsmith told me it was a Douglas, however i can't find a 1:10.5 twist on their web page. they only start at 1:12. I'm really hoping I am not getting a bad job done by this gunsmith. I've taken different stuff to him over the years and he has always done me right. I'm just starting to second guess things due to a new barrel having such an issue with the factory loads too. I thought that I had read somewhere as well that the faster twist was a good bet for the heavier 375 bullets?

A 1:10.5 twist will increase the rpm or spin of the bullet, compared to the 1:12, but should still be within reason IMHO.

Quote from: http://www.realguns.com/articles/200.htm
A twist rate is an indication of a means to an end. Bullets need sufficient rotational speed to stabilize, with rotational speed coming from a combination of twist rate and bullet velocity. A bullet, based on a good deal of empirical range data and analyzing tons of handload performance, needs to rotate near or above the 190,000 revolutions per second rate for optimal stabilization and good accuracy. Moving closer to and above 300,000 rpm tends to expose imperfections in a bullet's manufacturer with diminished accuracy and velocity as the symptoms. The formula for finding RPM is: MV x (12/twist) x 60

Twist rate calculator: http://www.realguns.com/calculators/riflingtwist.html