Recently picked up a 45/8" stainless super blackhawk and after shooting some factory cast through it got quite a bit of leading and quite poor accuracy. I realize the bullets may have been undersized.

I slugged the bore for a groove diameter of .429 and the chamber throats at
.433
.431
.432
.432
.431
.432

There did appear to be some additional resistance in the throat area suggesting some thread choke.

My expierence with revolvers is limited to a .357 6" Taurus and a 7.5" Redhawk 44 and mostly jacketed bullets.

My question is this, for those of you that have fire lapped a revolver, how did it affect the chamber throats? Where they of uniform size when you finished?

If you mean factory lead bullets; they are not hard enough and will lead; the cylinder is not the problem. I do put 11 degree barrel throats in them but with good bullets you won't get leading. Which bullets are you using and how big are they? When your cylinder throats are smaller than the bore that is what promotes leading; gas cutting is the enemy.

That was the impression I was under after doing some research on chambers being undersized which mine are not. I'm shooting Georgia Arms 240gr Semi-wadcutter Brinnel hardness of 18, MV of 1045fps. I don't know their actual diameter as I am out of them at the moment. The GA website lists them as .429.

.429 dia bullet may be too small for your barrel. May need a .430 or .431. Beartooth bullets sells a lapping kit, lapping bullets and specific instructions. I've used their kit, bullets ang formula on 2 Ruger 44s and will do a 45 Colt Ruger also. Made the 44s more accurate and easier to clean the barrels.

My Redhawk has cylinder diameters of 0.431-0.432". It leaded badly with the typical cast bullets, which are normally sized 0.429". With the RCBS 44-250K (Keith) mould, that measures somewhere between 0.431-0.432" as cast and run through a 0.431" sizer/lubricator die, it is very accurate and does not lead. Lube is a typical BP mix of beeswax/neetsfoot or olive oil, around 40% oil, with the amount adjusted to get the desired consistency. Just keep the oil above ~30%.

Clarence