Firearm Smith & Wesson 586 with a 6 barrel. The barrel was fire lapped a couple of years ago to remove a couple of restrictions.
The test was conducted using a Ransom Rest at a distance of 100 feet. About 120 powder coated rounds were fired after securing the Ransom Rest to the bench and the firearm to the Ransom Rest. This was my first time using a Ransom Rest and I wanted to work out any bugs before testing. There was no leading in the barrel after the initial rounds were fired.
Six rounds of powder coated .357s were fired and then six rounds of blue lubed .357s were fired and this was repeated seven times. The highest and lowest velocities and group sizes were tossed out and the five remaining groups were averaged.
Bullets All the bullets were cast using a Lee 358-158 SWC 2 cavity mold with the gas check shank area honed out to cast plain base bullets. The alloy was miscellaneous lead from various sources with 2% tin added. The bullet BHN was tested one week after powder coating or lubing with a Lee Hardness Tester. LBT Blue was used to pan lube the blue lube bullets. The BHN of these bullets tested 11.8. I used the shake and bake method with Harbor Freight Red to powder coat the PC bullets. The BHN of these bullets tested 11.0.
Loading I used once fired Starline .357 brass that was all trimmed to identical length. The primers were Winchester Small Pistol Magnum. The powder charge was 6.7 grains of Ramshot Zip. Each charge metered from a Redding 10X powder measure and every fifth charge was checked on an RCBS 10-10 scale.
Results I averaged the velocity and group size of five, six shot groups for each bullet treatment. The blue lubed bullets produced an average velocity of 1112 fps with an average group size of 2.3 inches. The powder coated bullets produced an average velocity of 1079 fps with an average group size of 2.0 inches. So, it looks like the blue lube gave about 3% better velocity and the powder coating gave about 13% better accuracy.
The only difference in the testing was the BHN of the bullets.
This year I have replaced the mold with a NOE brass 4 cavity with temperature probe and the powder coating with Smokes Carolina Blue. I am expecting better and more consistent results, but wont know for another year.