Cal and Lou,
Having used my Taylor's Spencer, and seen the results firsthand of use of originals in the same 'caliber',,, 56-50, I can honestly state that there have been no instances of any unusual or accelerated target damage from their use either at Johnson County Rangers, or at Hooten Old Town. Great Lakes Freight and Mining Co. has had the same findings.
Out of curiosity several months ago, I conduclted several trials complete with chronograph. The average velocity for the 56-50 Taylor's was 900 fps. from the carbine with its 20" barrel. Foir comparison, 45 Colt loads from a '73 Winchester with smokeless cowboy loads was 1250 fps. I ran the calculations for energy, and the results were basically even. Even with a heavier bullet (100 gr.), and a larger bore size, they are neck and neck as far as kinetic energy. These loads were with full capacity charges of FFG Goex, 34 gr., and a 350 gr. bullet. The 45 Lc. was with 255 gr. bullet, and 8 gr. Unique.
These results are easily verifiable by anyone with a chronograph, and a copy of Lyman's Cast Bullet Handbook for the formula.
The decision of allowing or not is up to your posse, this is only offered as a bit of information for your consideration.
Have a Merry Charistmas, see you at the Convention, I hope.