Leading in the first 1/2"...

[LeadThrower]

Please confirm or correct my understanding (which is based upon combing through this forum):

If I'm getting leading in the first half inch of the rifling and none in the rest of the barrel, chances are good that my cyl throats are a little undersized? I've tried air cooled (BHN ~12) and hardened (~27) alloy with unique and AA#9 in charges that range from starting to maximum (even light loads w/ unique). Also, sizing (or not) had no effect on the signs of leading. It's not bad after 50 rounds, but if I can avoid the cleaning I'd like to. I use a wheel full of COW "leadbuster" rounds to clean out 99.99% of it. Lube is either LLA or a JPW/LLA mix.

Both as-cast and sized boolits fail the finger-pressure cyl throat push thu test (or perhaps my fingers are weaker than they outta be?)

Thanks in advance for your insights!
LeadThrower

[shooting on a shoestring]

A few questions first.

What caliber? What boolit? What revolver?

But, to offer an answer without knowing all the particulars, I'd first go with a better lube, assuming the boolit has a nice big lube groove or at least a couple of adequate ones. Felix lube can cure lots of evils. LLA, not so much. JPW hasn't worked for me.

I'm glad to hear your boolits don't want to drop through your throats, so probably your boolits/throats are good, question remains is the barrel groove diameter bigger than the throats. I'll guess probably not. I'd expect lots of serious leading if that was the case.

[Bass Ackward]

Your assumptions could be valid. But they could be all wrong too. So easy to find out.

Even if you can't measure a slug, you can always drive one through the bore and then see if it will slide through the throats. That gives you a solid answer one way or another about which is bigger. Then you can either stop there until corrected or you can move on to the next possible cause.

Is this a new gun? Get an LED light and look in the forcing cone. See what you see. The white light of the LED will show more than a yellow light sourse.

If the forcing cone looks like a circular file, then chances are it's acting like one too.

Could be lube too. But lube quality is often a cure for something else that is wrong.

After it is all said and done, sometimes PB will just lead no how perfect conditions are. But you have to know what you are fighting with mechanicals of throat to bore relationship first.

[LeadThrower]

*slaps forehead* Don't know how I failed to get it in there, but these are Lee 158 RF boolits in my 357. -- Thanks for the lube comments, Shoestring. I'm still fixin to get the Felix ingredients.

*slaps forehead again* Bass, I dunno how I'm so stoopit as to not have thunk of the slug bore - slug cylinder concept. Everyone has to lose their sunglasses on their own head once in a while...

On closer inspection with the white LED, there are some tooling marks that make the cone look like a circular file in a couple places. What's your recommendation for treatment?

[Bass Ackward]

On closer inspection with the white LED, there are some tooling marks that make the cone look like a circular file in a couple places. What's your recommendation for treatment?


Hard to say because you didn't say how old the gun is. If it only has 500 rounds through it and that's all the tool marks it has left, then keep shooting it and just brush it so that lead is polishing steel.

You still must answer the slug question first. That is a show stopper if it goes against ya. but you have many options depending on your patience level.

[2 dogs]

My money says you have restriction at the barrel threads. Get some lead fishing weights...push one all the way thru and measure with a micrometer...then use a nail or pin and push another one into the muzzle and carfully pull it out with the nail and measure...the one that went all the way thru should NOT be smaller than the other one.

The cure is firelapping.....I use the kit from beartooth. Works great. Be sure your cylinder throats are correct...you cannot measure them accurately with a caliper....pin guages are the best way, but a jacketed bullet will tell you if they are too small...

[Lloyd Smale]

Personaly i think that if it were a lube problem or even a constriction problem it would show up in the whole length of the barrel. My guess is you have poor alignment between the clyinder throats and the forcing cone and your bullets are hitting the forcing cone with some yaw to them. Ive also in the past had a sizer die that was opened up that was not truely round and was producing oblong bullets do the same thing. that and bullets seated in a case not pefectly straight will do it but both of them usually show up as leading in the throats of the cylinder too. Id take a good long look at alignement and the condition of your forcing cone and how much side to side play the cylinder has.

[runfiverun]

i think i am with Lloyd on this one
you may just want to have the forcing cone re-cut
this used to be the thing to do right out of the
box as the threads in the frame caused tight spots here .

[lovedogs]

Have you considered the age old cure of just shooting a big pile of hot loaded jacketed bullets through it? I know that's blasphemy here but it sometimes is the easiest and most fun way of fixing it.

[LeadThrower]

... for my GP100:
Barrel slug drops right through each cyl except one needs the impulse of a mosquito landing on it to get it through, so no small cylinders.
Cast up my slugs from some pure Pb I acquired, and groove measures 356, lands 348 (5 grooves, so this isn't a simple measurement -- I don't have a V-jig to make it easier)
Slugs from cylinders measure 3575 (using dial calipers) consistently (one was more like 3572)
Gun age: "lightly used" before I picked it up, for what that's worth. I've put somewhere around 500-600 cast through it.


Lloyd -- I have gotten some lead from the cylinders, and the cylinder alignment isn't perfect. At lockup there's a tiny bit of play, but I don't have the means to measure it.
Lovedogs -- I like your scheme! Worst case would be no change in the gun with a few more dead cans! :Fire:

Thanks for your input, everyone!