Just a quick question. Genuinely interested in the answer.
How does S&W rifle the barrels on the revolvers currently?

Is it cut rifling or cation rifling?

ECM currently. Here is a link that might be of some interest. ECM rifling and my leaded up barrel...has ECM been the problem all along?! I bought a PERFORMANCE CENTER(R) Model 625 | Smith & Wesson which has deep cut broached rifling 3 years ago.

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Steve
The Lounge Rant Master

Rimfires are cut rifled. Centerfire regular production is ECM.

I have one IL revolver, an M617 10 shot 22 LR. It leaded with enthusiasm -- shoot 50 rounds and there is a real problem. After I finished reamed the cylinder of all my 22 LR revolvers, leading stopped.

I believe my other S&W guns are pre-1995, calibers include 9 MM, 38 Spl, 357 mag, 40 S&W, 44 mag, 45 ACP. I shoot very few handgun jacketed or plated bullets, but 98% home cast and lubed lead bullets. I've used various mixtures of paraffin, bee's, and candle waxes mixed with Johnson's paste wax or Alox. What I learned that eliminated leading in WC and semi-wadcutter bullets, regardless of caliber or velocity, was the addition of Dexron 3 automatic transmission fluid.

I took what ever lube batch I had, a full 3# metal coffee can, heated it on a hot plate outdoors, poured enough to 3/4 fill a 1 quart pot, added 1/4+ to 1/2- cup of ATF. Stirred the mixture on low to medium heat for 10 minutes, then poured into "my" 9" x 13" aluminum cake pan. I than placed the cake pan in the garage refrigerator to harden. After an hour of cooling, the entire block fell out of the cake pan.

I am not going to expound on throat diameter, bore diameter, exact lube mixtures or proportions, or alloy composition. All that is on the Cast Bullet Forum. I'm just stating that adding ~
10% ± ATF to my lube eliminated all leading in pistol calibers.

I have loaded 40 rounds of 45-70 using this lube (compared to "factory" rifle lube) and had no leading in a 32" barrel with excellent accuracy at 100 yards in a Taylor's Arms Sharp's replica Quigley.

Sorry for being a windbag, I just wanted to offer my solution to leading with home-cast bullets.

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S&WHF 366

I haven't found the type of rifling to be a deterrent to shooting cast or swaged bullets accurately, IF everything else is good. 629-6s are some of the best shooting .44s I've ever run.