Ok, here's the scoop on the 10ML-BP differences, straight from the mouth of Joe DeGrande.

1. Ramrod thimble is shaped differently and is a little longer in length
2. Breech plug now has a hex nut on the back rather than the 4-slots for the old removal tool.
3. 2" longer barrel
4. Barrel is a large shank rather than the standard shank like on the other 10ML-II models.
5. Action screw spacing on the BP is 4.40" to match the new centerfeed centerfires, while all other 10ML-II's still use the old staggered-feed spacing of 4.275"
6. These are only recommended for use with black powder or an equivalent substitute. NO SMOKELESS!

All other 10ML-II's will still come with the old style breech plug and ramrod until their current supply runs out. Whether or not they will change the screw spacing and barrel shank diameter on these like they have the BP is still unknown.