Obturation II, bullet size?

[cpileri]

Dear Sir,
I sure didnt want to hijack the recent thread on obturation, so i thought to post anew.  ihope that's OK.

When trying to load for a Model 71 Mauser, given that the bore slugged out to be .433 lands and .451 grooves, what size bullet shoudl i use?

The loaded ammo available from Buffalo Arms and grafs have .443 bullets, not paper patched.  Loose .443 projectiles are available.  So are .451-.452 diameter bullets.

I figure .433 bullets are too small to seal the bore, even with patching.
But, for safety and hopefully accuracy, would you go with .451's unpatched, or .443's patched with some paper that is 0.04-0.045 inches thick patched around it?

For informational purposes, the 71 Mauser original load was for a 380-ish grain paper-patched lead bullet in front of 77gr of black powder, pushing ~1450 fps.  I understand BP helps seal the bore by obturating the bullet.

My choices of powder can be either 77gr BP Equivalent of Pyrodex RS, or Triple SeVen or ~30grains of H-4198.  I was advised however, that real black powder is both best for accuracy and necessary for obturation (giving the best accuracy?) because of the rapid pressure increase, as opposed to the progressive burning smokeless powders.

Any help appreciated!

Thanks,
C-

[Veral]

  If you are going to paper patch, patch them as large as they will chamber, winding on more than two wraps if you can't find a paper which works with two wraps.  Definately get them larger than groove or you'll have problems.

  I haven't played with enough black powder to be a good source of information on which powder gives best obturation, but don't believe that to be a concern if you get the bullets a bit larger than groove  to start with.

  I do know that many BP shooters play with bullet softness and balance it to the pressure developed with a compressed load, which is mandatory for black.  This trick is only necessary if the bullets you are using are undersized.  I've recommended to many, and made molds for them, that they use hard bullets 20 bhn plus, which are over groove diameter to start.  Every one of them has reported better accuracy than they had ever obtained with soft alloys, and no more fouling problems than with any of their best soft bullet loads.