Leading occurs when?

[Qtiphky]

How many rounds until this occurs? I bought 100 rounds for my wife to shoot through her 38 and the accuracy is no where near what the first 150 rounds were. I have cleaned the gun after each 100 rounds and am just wondering what could be causing the decrease in accuracy. None of the loads were reloads so I am not sure if this is the correct forum.

[Rangefinder]

Leading primarily occurs when:

There isn't enough lube
The pressure is too high
The bullet is too soft
The bullet is undersized for the barrel

Since these weren't reloads, my guess would be size. Have you slugged the barrel?

[CherokeeT]

When you cleaned the barrel, did you see any lead flakes come out on the patch ? Did you look down the barrel to see if there were any deposits in the barrel ? If there are remaing deposits in the barrel, they tend to promote more leading. I have fired 100's of rounds without degrade in accuracy from 1911's and revolvers using ammo with my cast bullets and properly fit to my guns. Another thing that can cause leading is revolver chamber throats that are smaller than the bore of the barrel.

[Unclenick]

And add to that revolver chamber throats where the lead has built up.

Open the cylinder and shine a flashlight into the back of the barrel. The most severe leading usually appears just a short distance in and can be seen from there. If it all just looks shiny, run a bore brush in and out once, then look again. The brush will scratch up the lead surface and change its reflectiveness.

If you need to get lead out, just spray the bore with a good grade of penetrating oil. Most shooter's use Kroil. I like PB Blaster, but it smells strongly, so it's an outdoors kind of product if you're not a bachelor. Anyway, let it sit a day. While that's going on, pick up some 100% copper scouring pads (e.g., Chore Boy brand). After the stuff has sat, take a bore brush that is one caliber too small (like a .32 cal brush for a .38 bore) and wrap a few strands of the scouring pad around it. Use those to scrub the lead out. The penetrating oil tends to get under the lead and makes it easier to remove.

There are other methods, up to and including Sharpshoot-R's lead solvent, No-Lead, the electrolytic Outer's Foul Out bore cleaner that electroplates the lead off to a rod in the bore, etcetera. But try the cheap way first.

To your original question, there is no fixed rate of leading as it depends on the condition of the bore of the gun. I shot about 3500 rounds of hard cast bullets through one of my 1911's one week without cleaning and got no leading other than faint, small streaks at the corners of the lands in the bore. Totally ignorable. I've also seen guns you couldn't put 20 rounds through without having a lot of cleaning ahead of you.

For revolvers a few special problem conditions occur. One is that manufacturers sometimes make the barrel threads too tight in the frame, and that squeezes the back of the barrel enough to allow gas cutting of lead bullets. You have to slug a clean, lightly oiled barrel with a pure lead slug to feel for that constriction. If you have it, you need to firelap the bore to remove it. That will also smooth the bore making it less prone to leading.

Another is the aforementioned issue of chambers being undersize. That's also common. There is a whole business that just does revolver cylinder reaming called Cylindersmith, this is so commonly needed. You want to slug your bore and chambers and measure the slugs to be sure your groove diameter isn't as wide or wider than your chamber throats. Chamber throats need to be at least half a thousandth bigger to do well with lead. If you are going to firelap, do that before having the cylinders reamed. It may or may not cure that problem for you.