I had a knew rifle barrel put on my 4570 Sharps I took it to our local guy he ream the chamber to match my bullets, it was -5 yesterday and temperature Rose to 15° I shot for four hours I run a patch through after every shot I use BP I noticed the steam in the barrow would freeze if I let the rifle set to long some of my bullets had excess lube on the outside the bullets,, the cold froze the lube made It hard to chamber some of them I had to add I A few minutes to my sites I was shooting the 500 and 725 yard targets they weren't covered in snow.
I think shooting frozen black powder loads made my 70gr loads sound like 65gr loads, I had to add a couple minutes to the sites they shot good.
I was amazed at how the condensation in the barrel would leave ice crystals in it.
The Krieger barrel Took six patches to clean no leading, this barrel is a large improvement over my last one money well spent.
If you ever send your 4570 shaps to have a new barrel put on send some of your ammo with it it's a pain in the xss when you get the rifle back and your bullets don't and never will fit, I was fortunate we had a local guy that shoots with us and he had a reamer, I took him some of my ammo and it took him less than an hour to match the chamber to my loads.