Rob, that's some fantastic shooting. BTW, I once almost bought a Withworth Express, and your grouping makes me regret the "almost" part. Here's my .375 H&H Flanged with RL-15 and a 270-gr Speer BTSP. Again, dying to try the Win 760.
I really like loads that work well and can be loaded right to the base of the bullet... but not compressed. 4350, either type, can be loaded in the 375 HH up to the base of either the 270 or 300 gr seated to a normal depth, be at 100% load density and do well. I think my 375 HH data for accuracy and SD of velocity very slightly favors Varget over 4350, but not by a lot. I also tried Reloader 19, it did well and was comparable to 4350. I shoot a bunch of 4895 type pull down powder for range time and paper and that also does fine in the 375 HH. Loading the 375 with normal bullets and loads is kind of like loading for the 30-06- matter of fact there may be some scaling effect in play comparing the internal ballistics of both cartridges.
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