Leading in S&W 686

[The_Last_Boyscout]

Can anyone give me any tips to help prevent leading in my revolver? Is it better to not try and shoot jacketed bullets and then cast bullets on top of that without cleaning. I am shooting the Oregon Trail bullets and they seem pretty hard. I have the 148gr lead wadcutter(very accurate and not much leading/3.5 grs of Win 231) and the 158SWC can't remember the load right now but it was'nt that hot, mild load but leaded up pretty good.
Any tips/pointers would be appreciated. I have been shooting for a while but have'nt figured this lead bullet thing out yet.
Thanks
Dave

[8ring]

Controlling leading in your revolver depends on a number of factors. The first is the size of the bullets compared to the throat diameters and barrel diameter. Hard cast lead bullets can work best when they are at least .001" over the barrel diameter. (I think that your Lasercasts are .358" diameter.) The best bet is to have a gunsmith slug your barrel and measure the throat diameters. You can test throat diameters on your bench by trying to push a jacketed .357" diameter bullet through the throats. If it goes through all the throats with moderate force, your throats are probably OK. If some throats are too small, your gunsmith can ream them all to .358+ diameter. Doing this reduced leading and helped the accuracy of my GP-100.

Hard cast lead bullets need sufficient pressure to obturate the base of the bullet and seal the bore from "blow-by" of hot gases that melts lead on the side of the bullet and causes it to accumulate in the bore. This kind of leading may often be seen closer to the forcing cone. For example, my GP-100 leaded more at 38 spl. velocities (800 fps) than moderate (1,100 fps) .357 velocities. The Cast Bullet Society, Richard Lee, and others have developed formulas that calculate the pressures needed to obturate bullets of different Brinnel hardness.

Another kind of leading occurs when the pressure and velocity exceed the lubricant's abilities and the strength of the lead. This may be seen closer to the muzzle. I've shot hundreds of 140gr hard cast .357s at 1,250 fps in my Ruger with virtually no leading. There was a slight dusky color near the muzzle that may have indicated that the lube had worn off but there was no noticeable lead build-up. With a properly sized lead bullet and the right powder, you may well exceed those velocities without leading.

Bullet hardness is the next variable, but this is difficult to control since most casters sell 92-6-2 alloy bullets. Mike Venturino, a gun scribe and cast bullet expert, maintains that 92-6-2 alloy is too hard for the vast majority of revolver rounds, including .357. If someone in your area casts bullets, you might ask if they can make a slightly softer alloy for moderate (900-1,200 fps) pressures and velocities.

Finally, look for single base powders or double base powders with low nitro content. Nitro burns very hot and powders like Titegroup (37% nitro) and Bullseye (40% nitro) can melt the base of the bullet, burn off the lube, and cause both leading and a great deal of smoke. All Vitavouri powders are single base. I've had good results with VV-N340 with lead and moly-coated bullets in .357. I think that IMR powders like 4756 are also single base. Unique is also said to be friendly to lead but I've never tried it.

If all else fails, buy a Chore-boy, wrap it around an old brass brush, clean the barrel, and try again. BTW, be sure to look for lead build-up in the forcing cone as well as the barrel.

Good luck,

Chris

[Hammerhead]

8ring has it down pat.
I used to think the harder the bullet, the better.
I load light target loads in .357 brass with Hodgdon Clays to about 850 fps for Speer HBWC's (swaged, soft lead-cheap and accurate) and 900 for commercial cast SWC's (bevel base).
The Speer HBWC's are as clean as jacketed ammo.
The cast loads lead the barrel prettty quick.
The hollow, soft base of the Speers seems to be the key to seal off the bore.
I'm going to try Hornady's swaged 158 SWC's for a replacement to cast loads. They have a good lube system for subsonic loads
Never shoot jacketed ammo after lead ammo. Shoot one type or the other between cleanings.
Some old hands will only shoot one type of lube/alloy combo between cleanings.

[Gib]

I shoot berry's copper plated bullets with my 38 reloads along with 231(Winchester) powder and federal primers. You get very little build up and the gun cleans pretty quickly. I use a moly coated lead bullet from bear creak for my .45 reloads and it cleans rather easily with solvent and a brass brush. I hope this helps-
Gib

[Hal]

Unique is also said to be friendly to lead but I've never tried it.

Unique is so/so.
(I use a lot of Unique - it's my "go-to powder")
It's fair for .38spl, but too "hot" for .357mag.
It's real advantage is that it generates a loot of soot. The soot seems to keep the lead from getting mashed into the grooves of the bore and a dry patch is all that's needed to push it out when it does accumulate.


BTW - outstanding dissertation 8ring.
IMNSHO - it should be a "Stickey" in the handgun and hand loading forums.

The cause of "leading" and how to avoid it is probably the single most misunderstood thing here.