How do u know if leading is happening?

[Buck-N-Rut]

I have been casting 38 special 152-154 grain swc and I have shot about 200 out of my 357 Ruger blackhawk. I am gas checking every bullet to be safe and using lee alox for lube. Sizing to .358 with 4.2 gns of HP38. What do I need to look for if anything with this load?

[destrux]

Leading would show up as streaks of gunk inside the barrel that don't clean out with a few patches. There's no mistaking it. It doesn't look like powder fouling or copper fouling. It's much thicker and the only way to clean it out is scrubbing with a bronze brush (lead remover helps, so does using pieces of chore boy scrubber pads on a brush).

You would have seen it within the first 100 rounds if you were going to get much of it. When my .40S&W was leading really bad it would lead the barrel with one or two shots.

[LtFrankDrebbin]

I will normally get a grey wash that can be seen in the bore of my wheel guns. It dont worry me because it remains just a grey wash for the duration of how many ever I fire between cleans.

The levergun however is a different critter, very hard to detect by eye from lube and powder fouling.
If it is leading from a particular load, first coulpe of patches during clean up tell me.
Flakes or even streaks of lead will be present on the patches.

[Shiloh]

Accuracy goes south in a hurry. If your groups start to open up, stop and check. If leaded, you can't miss it. Better to clean it out before it gets compacted. You wind up squirting boolits out the barrel rather than spinning them.

I had some boolits sizes at .358 fired through a .357 mag. I use a dental mirror to check. The groups started opening up. I stopped, cleaned with a .45 cal brush and tried again. Same pattern. My boolits where to soft for 1350 fps. I backed down the charge a bit to around 1225 or so and things were much better. This was relatively light leading caught early. I was able to clean every ten rounds or so to use up the loaded ammo.
I have since hardened the alloy for another try.
These are a flat base LEE 125 RN boolit that drop around 129 gr.

Shiloh

[CML]

Load sounds good. I wouldn't even be gas checking them. If they shoot good and you can look in the muzzle a bit and not see heavy streaking I'd say you are fine. When you get something that starts leading, you'll know it for sure.

[9-toes]

+1 on ditching the gas check. Just no need if you slug your barrel and size your bullet appropriately. I've been using the LEE 358-125 RNFP pushed with Bullseye or Trailboss for .38 and just love how it eats the center outta them bullseyes.

[Buck-N-Rut]

What does slugging my barrel have to do with a gas check? I'm lost on that one. Honestly.

[turmech]

They are saying to slug your barrel to see if .358 is right for your gun before switching to a no gas checked bullet. That gas check could be making up for the incorrect size if in fact the size was wrong.

Nothing wrong with slugging the barrel, but for me I would see if your 358 bullets are the correct size for your cylinder throats. The bullets should ideally require a small amount of force to be pushed through the throats. If they fall straight through your too small. Your throats will size whatever bullet your shoot to there dimensions no matter what size they start out at. As long as the throat is the same size or larger than the bore your good.

The 38 special does not need gas checks. But you would be better severed by choosing another mold which does not cast GC bullets rather than simply omitting the GC from that bullet.

[MBTcustom]

Slug the barrel by pushing a soft lead egg sinker through it, or cast a boolit out of soft lead and smash it a little to make it for sure bigger than your barrel. Push it through with an aluminum or brass rod from the hardware store (stay clear of wood, and steel). Measure it with a good quality micrometer (not calipers) You are after the groove diameter. Make sure your boolits are .001-.002 over size, and if you are shooting COWW alloy, or perhaps 50/50 COWW/pure lead, you can push them up to 1500 with no gas check. If you start getting above 1500fps, it gets difficult, but I have pushed COWW with a plain base, all the way to 1800fps before I started to get leading no matter what. You just gotta get the fit right.
A few other things that you need to watch for:

Slug the throats of your revolver too. (Notice I said throats plural? they can be different sizes.) Make sure that the throats are equal to or greater than, the groove diameter of your barrel, otherwise your over sized boolit wont do you any good at all.

Make sure that your brass is not sizing down the boolit as it is seated. Pull a few boolits to make sure.

Make sure you dont have any "thread choke" going on. This is where the part of the barrel that is screwed into the frame is sized down by the pressure, and it will cause your boolit to be sized down when it passes through that first 1/2 inch.

If there is anything else that you do in the process of loading your boolits, that has potential to size the boolit down, diagnose it, fix it, and move on.

[Buck-N-Rut]

Lots of great info. So tell me this... Why is it that I don't have to slug my barrell when I buy factory ammo off the shelf? Again, just trying to learn.

[destrux]

With jacketed bullets there is no lead for a gas leak to melt lead off the sides of the bullet. You're probably talking about factory lead bullet ammo though...

With factory lead bullets some guns will still lead the barrel and get poor accuracy if the bullets are undersized. I have a .32 H&R magnum revolver that leads terribly with factory lead round nose ammo. Does fine with wadcutters though I suppose because they are loaded lighter. So if you're not seeing any leading with factory lead ammo then its just good luck.

[Buck-N-Rut]

Do I guess that just answered my question. Leading is caused my too small of a bullet. When the gas get on the side of the bullet and melt the lead as it is exiting the barrell is what actually causes leading. So the bullet always needs to be a fraction larger than the barrell diameter.

[MtGun44]

"The bullet always needs to be a fraction larger than the barrel diameter."

BINGO! We have a winner.

Too big MAY cause chambering problems in a minority of guns. Too small will be inaccurate
and lead the barrel. Easy choice.

Bill

[Shiloh]

Lots of great info. So tell me this... Why is it that I don't have to slug my barrell when I buy factory ammo off the shelf? Again, just trying to learn.

You do, when and iff you are buying lead bullets as components.

Most commercial 9mm cast bullets are sized at .356. To small for most 9's on the market. Many of the available .30 cal cast lead were sized and gas checked at .310. Worked for many but not me. I get much better results at .312 in the Krag and Springfield.

Shiloh

[What The Chuck]

When you say a fraction you mean??? one or two thousandths??