24 April 2015
I wonder if your bullet is too small in the “bore-riding nose” section?
Your Lee 185 is a nominal .312” bullet, which might drop as large as .314” on the driving bands, if you're lucky and your mold runs a little large. That diameter is probably fine for your Mauser, since two wraps of note book paper would increase the patched diameter to .324, or thereabouts, on the driving bands of the bullet.
The problem comes in with the dimension of the bullet's nose, which was intended to ride the tops of the lands in such rifles as the 7.62x54R Russian, .303 Brit., etc. As a result, your bullet's nose, as dropped from the mold, is likely in the neighborhood of .303” or slightly smaller, and when patched would only stretch to .313” at best.
Thus, half of your bullet's length (the nose section) would be supported on the tops of the Mauser's lands by nothing more than the .010” thickness of paper overlying the .303” lead nose beneath. Such a bullet is very likely far too free to wobble about on it's trip out the barrel to shoot accurately.
I think you'd be much better served by a bullet measuring .314'' or so along the entire length of the bullet body. The reduced nose diameter of the “bore-rider” bullet style, in my opinion, is poorly suited to paper-patching.
Why not try patching the Lee 175-grain 8mm Mauser bullet, after sizing it down to the .314"-.316” neighborhood? A two-wrap patch of note paper would then bring the PPB diameter up to about .324"-.326” along the entire body-length of the bullet, and would likely suit your Mauser much better than the smaller-diameter Lee 185-grain bullet.
Hope it works for ya, and, happy trails,
-- Cary Gunn --