Berrien Moore: I will go out on a limb here and guess that a point made "over your head" may have concerned the question of overstressed rifling. That is a phenomenon unique for the most part to either homogenous bullets designed without any pressure relieving grooves or bands, OR maybe heavily steel jacketed solids. The effect has been to bulge the rifling slightly to the outside of the barrel, appearing rather like the spiral on a hammer forged barrel by Mannlicher. This has occurred on certain older double rifles, and fear is that the slender barrel profile on a drilling barrel might be even more vulnerable. Many drillings, and I am sure yours is one, are marked "suitable for steel jacketed bullets" (stahl mantel gechoss) but the outcome is not guaranteed. Proceed with caution.
Pictures of your drilling would be most welcome, as well as a description. Is it equipped for scope, etc.
