Odd no one bothered to actually go to the rim rock website and look that bullet up. All their "Cowboy action" cast lead bullets are 15bhn

15bhn ='s lyman #2alloy
lyman #2 alloy ='s max pressure/loads in their reloading manuals

You couldn't drive those bullets hard enough/fast enough in a 44mag (including rifles) to get leading from those bullets. The 2 main concerns you should have with them are:
1. The diameter of the bullets. They are .430", your 629-4 should eat .430" bullets like popcorn. Just keep the pressures up to make sure the bullet seals the cylinders/bbl. Too little pressure and you'll get no seal which leads to flame cutting/leading.
2. The rock hard lube needs pressure to do it's job. Less pressure ='s less performance. Leading and lack of accuracy are the results of lube failure.

Lyman #2 alloy in a 308w:
Cast up some lee 160gr tumble lube bullets and lubed them using a traditional 450 lyman sizer and lbt hard blue lube. The small tl rings held the lube. Did a ladder test using H335 taking the test loads up to +/- 38,000psi.


I didn't have any leading, this told me I didn't have enough lube. I used the same bullets above and tumble lubed them with 45/45/10 and re-tested.


The 37gr/38,000+psi re-test


While nothing to write home about (2 moa), it's a place to start with cast bullets, high velocities, high pressures. Any time you use/shoot cast bullets you want to see a lube star on the crown of the bbl. That's how I knew I had a lube problem with the initial 308w test pictured above. 50+ rounds down the tube with no leading and very little lube star on the muzzle. What the crown looks like with the blt lube + the 45/45/10 lube and only 15 shots.


Nothing to write home about but the re-tested highly lubed bullets managed to do 2 moa. Not too bad for a 38,000+psi load doing 2600fps+ @ 100yds. When you test you need to do the same thing, look for leading, star lube and then finely accuracy.

You can't drive those 15bhn bullets hard enough or fast enough in the 629-4, a levergun, contender or anything else to get leading. Leading comes from in-proper fit, lack of lube/wrong lube for the pressure of the load.