sellor bellot wadcutters, 38

accurate double action, not so much single action. Not my usual results shooting period.. 

However, are these known to be masters at leading chambers up? I only fired 20 cylinders, but my gun looked like i was shooting swagged swc at keith velocities again.. Had actual flakes of lead on the crane, forcing cone, and even smeared on the cylinder. 

but my gun is in proper time..

Any S&B Wadcutters I’ve shot have been accurate enough in my 52 but it isn’t like the RedBox Federal.  I haven’t shot enough to see any issues.

They were just bought out 12/18.

Pull bullet. Measure diameter. Diameter should be the same as the barrels freebore(?) or 0.1 mil larget, and at least 0.1 mil larger than barrel groove diameter. If diameter is too small, you get gas cutting with lots of leading.

What's a mil ?

In the FWIW category: I have used Sellier & Bellot .38 Special 148 gr HBWC in a Colt 1851 .36 caliber replica equipped with a Howell .38 LC conversion cylinder. Yes, the cylinder is long enough to accommate this .38 special loading (where the WC bullet is just a scooch above the case mouth). As an example, after 42 rounds I did not experience excessive leading and the clean-up was no more cumbersome that for my other center fire revolvers using lead bullets. Now this is for a barrel with nominally lands at 0.360" land and 0.372" groove diameters. It works so well because the the skirt of these hollow base bullets expand to fill the bore and virually eliminate blow by of powder gases.

The european website of SB talks about their components.. the 148 HBWC is supposed to be  .357 diameter same as there entire product offering in 38 sepcial and 357 magnum.