What bullet w/ BP?

I have a 43 Mauser 1871 I want to shoot bp in. What bullet do I shoot. It has .454 grooves and .433 lands. Do I need to fill the barrel with the bullet? Or can I shoot .446. Hawk bullets because they are jacketed.
It’s a special problem to be sure. I could PP but to what diameter? Or sell the gun. It’s a m1871 barreled action with custom stock and set triggers. 25 inch barrel, pristine bore in very good shape. Professionally done hunter or stalking rifle and antique.

I really just want to know what to shoot in it.

 

Wikipedia says it takes a .446 dia. cast lead bullet of 370 grains weight. The rifle is not made for jacketed slugs and they might not be very good for the bore.

 

That’s the groove of the 71/84. This seems like it’s different technically speaking. With my groove that bullet would gas cut.

 

I think you can use a 405 grain 45/70 (.457) lead bullet sized down to .452 without a paper patch.

There's a lot of good info for you here:
https://castboolits.gunloads.com/showthread.php?37613-Mauser-Model-1871

 

Might be worth trying a.452 pistol bullet, my trapdoor likes a 255 grain .452 much better than the .405 gr standard ,458 plus it don't beat ya to death.

 

Google 43 Mauser or 11x60 Mauser and you get lots of stuff.

Midway lists a Lyman mold for the bullet. Presently out of stock, but someone may have one for sale. It gives you something to look for, if you cast your own:

https://www.midwayusa.com/product/1010244253?pid=705018

 

I appreciate the info about bullets that fill the bore, but how do you push them into the case. I’ve never had a PP bullet that didn’t bunch up on top of case. I used a .439 bullet, 2 wraps of .0025 paper.

 

I thought of using a .452 plated bullet. Soft lead. But won’t .433 lands distort it badly?

 

What will happen. It will have .010 engraving on either side. Will the pressure rise.

 

Don't use soft lead in it and don't use jacketed bullets. Soft lead will strip through the rifling and lead your bore up fast.

 

Soft lead will obturate and fill the grooves. If you wish to go the PP route, bell the case mouth a bit more than you normally would. One of the first rifles I loaded for was a 44-40. Grandpa taught me that soft lead was best for BP loads. Properly lubed = no leading.

 

At 1,430 FPS soft lead will most certainly strip through the rifling.

 

How soft is too soft? I was hoping for 9- 12.

 

9-12 brinell would probably be fine. If the accuracy isn't there try softer.

 

You might get by with a BHN of 12 but 17 would be better. Try it and see.

 

if hardball is 15 what would be 17?

 

90% lead, 8% antimony, 2% tin.