I could use a little advice as to proper sizing diameter for a Super Blackhawk 4 5/8" for running cast bullets.

I've slugged the bore at .429" and the cylinder throats at:
.433
.431
.432
.432
.431
.432

I have fired the Georgia Arms, 240gr Semi Wadcutters at 1100fps and they lead terribly for the full length of the bore. Interestingly those same loads don't lead my redhawk much at all. It's bore also slugs .429. Not sure about the throats as I ran out of sinkers.

My intent is 200-240grs in the 1000fps range give or take a bit and I'm hopping to run a plain or bevel base without a gas check.

Any advice you guys can give me as to proper sizing to alleviate the leading issue would be much appreciated.

I size mine at .430 for any of the 4 44s I own.

I use all hard cast made out of mainly wheel weighs and have limited leading problems.

Try them sized to your cylinder throats.

I have seen bullets sized to 0.432" to function properly in a Ruger. I size mine to 0.430" and have no problems with leading.

All I have shot for years in my .44 SBH are home cast sized at .430 . All I shoot are cast, powder coated and sized to .430
What are you using for Lube? You should not a lot of leading with the right lube and sized to .430 Take a look at powder coating your bullets.

Thanks guys for the advice. I'm hoping the leading was due to undersized bullets, but it does still puzzle me as to why one gun would lead and the other one would not. I slugged both of them twice just to be sure.

I've got to wait a few weeks to find out now due to getting into a bit of a hurry with a mandolin slicer, but look forward to getting this gun sorted out.

The .429 is not being determined by the "infamous" Ruger choke spot where the barrel goes through the frame is it?

If so, that could explain why one of them leads and one does not.

Might also be a slight rough spot in the barrel unless it just leads in general down the barrel.

Decided to give it a whirl this weekend since my thumb is finally in usable condition again. Loaded up some 200gr XTPs with 10.5 and 11.0 grs of Unique. 25 rounds of each later the 11.0 load averaged 3.5"(best this gun has ever shot) at 20 yrds, the 10.5 was terrible. Not as much muzzle blast and recoil as the normal 300grn xtp loads I shoot in my Redhawk or factory 240's, but still more than what I'm looking for.

The barrel/frame junction choke point is a possibility, I don't recall extra resistance at that point, but its been a while since I slugged it. Other than firelapping how does one go about fixing a throat constriction?

I noticed Dardas offers their bullets in .432" might order 100 just to try, I can always feed them to my Marlins if they still lead.

You can always lap the barrel with some JB Bore Paste on a patch over a brush. That will smooth out the bore and should cut down on leading. Of course, you are going to have to match the hardness of the bullet to how fast you are driving it.

I have seen .452s shot down a .432 bore and show no significant leading. So I wouldn't get all hung up on that.

#1 I would ream the cylinder to .433 so they are all the same size. If you can't do this there is a guy on Cast Boolits that does this service for a modest fee.

#2 I would then size cast bullets to .433

#3 I would make sure you're using a good lube. Many cast bullet manufacturers use a lube that is to hard and doesn't lubricate the barrel well and you end up with leading even if you have proper fit.

#4 Make sure your barrel is completely free of lead and copper fouling before you try shooting them again.

Doug would probably recommend cutting the throats to 4325.
[he is DougGuy over at the Boolits site]
if you have a constriction under the frame [common on the rugers] fire lapping will make it better.
you want soft lead bullets and a slower load to do that job.