The grip fills your hand out and it limits movement. Plus, Jack Huntington (who did all of those grips) removes a little grip material that gives you more clearance. When I endurance tested the new .480 Ruger Super Blackhawk Bisley, I had a knot on my middle knuckle from repeated contact. However, when I would shoot my .500 Maximum (with a Huntington modified and gripped Bisley grip frame) off the bench, the only time the trigger guard would make contact with my knuckle is if I didn't use enough grip tension. Otherwise, it wouldn't hit my knuckle at all. Doesn't seem like it would work, but it makes a world of difference.
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