.357 Magnum PC Leading Issues

[TXCOONDOG]

I'm getting leading in my GP100 6" even though my cast boolits are powder coated and sized at 358" . The leading is taking place in the forcing cone and the first 1/2" of the rifling.

My alloy is WW + 2% tin with a BHN 17.

All my coatings past the hammer test with no flaking, etc.

My cylinder chamber measures at .356.5"

My velocities are around 1250 fps using blue dot.

Can the boolits still be to small with just enough room for the PC to get damaged causing the leading to occur ?

Any help or ideas are greatly appreciated.

[TXCOONDOG]

After cleaning out the leading, I fired one round and I can see small pieces of lead at the beginning of the rifling so maybe my lead is to soft ?

[unique]

Actually it may be to hard and/or PC not providing enough lubrication. How many grains of BlueDot are you using?

I get something similar in my GP100 at 10gr BlueDot and have traced it to not enough lubrication.

Try waxing a couple load rounds to see. I take Johnson paste wax and wax the outside of the bullet. You can do this with any lubricant...just don't over do it. If leading is reduced then start thinking about not enough lubrication.

Good Luck.

[TXCOONDOG]

10grs of BD. I thought about it being too hard as well and also thought about sizing to .357 to see what happens.

I don't have any paste wax but I do have alox to try.

[Bzcraig]

Are you checking your Powder coating with the smash test?

[TXCOONDOG]

Are you checking your Powder coating with the smash test?

yes

http://img.photobucket.com/albums/v91/kennygates/Mobile%20Uploads/4350E4D0-008E-4B66-AB76-BA3C5A2A2592_zpsfmrpetki.jpg (http://smg.photobucket.com/user/kennygates/media/Mobile%20Uploads/4350E4D0-008E-4B66-AB76-BA3C5A2A2592_zpsfmrpetki.jpg.html)

[Bzcraig]

DougGuy is our resident revolver smith you can PM him or wait he should be along soon.

[BNE]

Sizing to .357 should make it worse..... Try going bigger if possible. Clip on WW + Tin should be hard enough for that speed. I use a 50/50 (COWW / Pure) plus tin that works fine.

Also +1 about Doug Guy.

[unique]

Here's something I do when trying to find root cause of leading=> Fire gas check bullet to prime/clean bore. Tilt muzzle down before firing to move powder away from the primer (lower velocity).

Check bore and if need be fire gas check bullet to prime/clean bore.

Tilt muzzle up then slow level firing position to move powder closer to the primer then fire (higher velocity). Check Bore.

I have found 10gr BDot to be somewhat powder position sensitive and have seen muzzle up versus muzzle down give 200fps difference so essentially you are testing identical load but at two different pressures.

As an aside, I view running out of lubrication (leading near muzzle) differently then not enough lubrication (not enough lubricity for forces encountered).

Good Luck and please let us know what you find out.

[Bzcraig]

How good is boolit fit in throats? Your boolits should fit into the cyclinder throats with some resistance with your finger. Are all the throats the same size? I agree with BNE, try bigger first.

[Smoke4320]

I would try 5 bullets at 359 and paying attention each shot for leading

[wgg]

Have you checked for thread choke, where the barrel screws into the frame. I had this with a Bisley 44 Special. I fire lapped it and now no leading, with powder coated SWC or RFN.

[Calamity Jake]

yes

http://img.photobucket.com/albums/v91/kennygates/Mobile%20Uploads/4350E4D0-008E-4B66-AB76-BA3C5A2A2592_zpsfmrpetki.jpg (http://smg.photobucket.com/user/kennygates/media/Mobile%20Uploads/4350E4D0-008E-4B66-AB76-BA3C5A2A2592_zpsfmrpetki.jpg.html)


That's a gas checked design boolit, your getting gas cutting from the smaller GC shank
not being unable to upset and seal the bore, put a gas check on it, problem solved,
or use a FB boolit.

[NoAngel]

Pull a seated bullet and make sure you're not shaving lead. Also, I have often wondered about roll crimps. Could a stiff roll crimp shave coating off the bullet as it exits the case?

It's worth a few rounds to find out, try a lighter crimp OR go to a taper crimp.

[mdi]

Are you absolutely sure it's leading? Or maybe just PC fouling?

[unique]

One more idea is to recover a fired bullet and look it over for clues...

[jcren]

What size is the cylinder mouth? It may be scraping your pc.

[OS OK]

Maybe you need a weelittle more angle in the throating, possibly doesn't have enough? I dunnoh.
Is this cast the first cast to do this or the first time you ever noticed it?

[runfiverun]

your cylinder throats are too small.

[OS OK]

your cylinder throats are too small.

I discounted what he said about the cylinder throats, thinking he meant barrel throat...if he is correct, how do you get a .358" round in them in the first place?

[TXCOONDOG]

How good is boolit fit in throats? Your boolits should fit into the cyclinder throats with some resistance with your finger. Are all the throats the same size? I agree with BNE, try bigger first.

Yes on all accounts.

All,

Let me look at some of the things pointed out. Yep, the boolit pictured is a gc design and I was lead to believe that it would work with PCing and no gas check. I did cast some TL358-158 last week with a current BHN of 13.4.

Thanks for the ideas thus far and I will eliminate them, one at a time, as being an issue.

[TXCOONDOG]

I just seated a few boolits with a heavy crimp (redding profile crimp die), used a kinetic bullet puller and found no damage to the coating of any kind.

What grit sandpaper and what size dowel works best to open up the lee sizing die or is there a better method ?

[jcren]

I used 600 grit on a pencil sized dowel. Lubed with light oil and chucked into a drill.

[Mitch]

Is it correct then your cylinder throats are .3565.then what is the barrel slugging at?it should be .357.is this is the case you need to open the cylinder throats to .001 to .0015 over what the barrel slugs.your boolit is being sized under by the cylinder throat.this will lead up a revolver as you are describeing every time

[OS OK]

If he isn't using the correct expander, he's got a re-swage right in the seat die to start with...too many loose details in this thread.

[runfiverun]

they are tapered cones.
the whole system should be tapered cones just going smaller until the last one is just a tube.

[rusty marlin]

Is it correct then your cylinder throats are .3565.then what is the barrel slugging at?it should be .357.is this is the case you need to open the cylinder throats to .001 to .0015 over what the barrel slugs.your boolit is being sized under by the cylinder throat.this will lead up a revolver as you are describeing every time

^
||

That's the answer.

You told us the dia. of the throat but not grooves in the barrel.
A lead bullet must always be getting sized smaller by a revolver. .359 as loaded, .358 cylinder throats and a .357 groove dia. would be ideal.

[TXCOONDOG]

181438

Barrel slugged at .356

[Gohon]

your cylinder throats are too small.

I think the above is correct. My opinion is your casts are to large and to hard. Drop the size to .357 which puts them at the ideal size of .0005 over cylinder throat diameter and hardness to 11-12 BHN so they can bump up after the forcing cone and I think your problem will go away. This of course assumes your measurement of .3565 is correct for the cylinder throats. If you are simply measuring the throats with the dial indicator then you're not getting a true measurement.

SAMMI specs 357 magnum cylinder throats at .358 inch. You should be able to force a cast through the throat with thumb pressure. Have the throats reamed or reduce cast bullet size....just my opinion.

[Moonie]

181438

Barrel slugged at .356

Calipers are not generally considered accurate enough for this measurement, please use a micrometer.

[unique]

My experience has lead me to believe that a lower BHN and a good lube is the way to go.

Here is a test I ran this morning. I have GP100 with bore of 0.355" and cylinder of 0.357".

I loaded with 10gr BDot and 150gr SWC PB size of 0.358"with 18BHN and a hard lube in the groove. Velocity was 1219fps. This gave good accuracy and noticeable leading.

I loaded 10gr BDot into 358665 PB size of 0.355" with 11BHN and soft NRA lube in the groove. Velocity was 1246fps. This gave good accuracy and zero leading.

[TXCOONDOG]

I tried the alox, the boolit sized at .358" and had pieces of leading at the beginning of the lands.

I sized to .357, my accuracy improved (1/4" tighter) and got very small specs of lead (almost nonexistent).

I do have other powders such as H110 and MP 300 which I can increase the velocities to see if things improve with obturation.

I'm very new to casting and not sure if I should just resize to .357" and increase my velocities with my current castings or just recast for a lower BHN as suggested by others.

I've learned a lot with casting and reloading which has opened up my eyes to understand my firearms.

Geuss at this point, I'll sit back and think about things.

By the response on my measurements, I'll start looking to upgrade and adding more precise equipment after the holidays.

[DougGuy]

DougGuy is our resident revolver smith you can PM him or wait he should be along soon.

Funny.. You guys know me too well.

First off, it matters not what you size to if you have .3565" throats, boolits will come out of the cylinder at throat diameter. You are only sized to .358" until you drop the hammer ;)

Reaming the cylinder throats to .3585" ~ .3588" would have you presenting your sized and PC'd boolit to the forcing cone at the diameter they were when they were sized and PC'd and not sized down by the cylinder throats. You cylinder is currently acting as a 6 port sizing die.

If you address this problem, I am willing to bet the leading will disappear completely.

Our site is currently experiencing issues getting and sending PMs so if you go to the facebook link in my sig you can contact me there if you need to, or you could try clicking the user name, then click send email and it will send an email to the user's registered email address and not to the Inbox on the site.

[TXCOONDOG]

Funny.. You guys know me too well.

First off, it matters not what you size to if you have .3565" throats, boolits will come out of the cylinder at throat diameter. You are only sized to .358" until you drop the hammer ;)

Reaming the cylinder throats to .3585" ~ .3588" would have you presenting your sized and PC'd boolit to the forcing cone at the diameter they were when they were sized and PC'd and not sized down by the cylinder throats. You cylinder is currently acting as a 6 port sizing die.

If you address this problem, I am willing to bet the leading will disappear completely.

Our site is currently experiencing issues getting and sending PMs so if you go to the facebook link in my sig you can contact me there if you need to, or you could try clicking the user name, then click send email and it will send an email to the user's registered email address and not to the Inbox on the site.

Email sent.

[mdi]

I think I'd start again. Accurately measure the cylinder throats and groove diameter (forget "push through", "snug push through", "drop through", etc. as those are not measurements. Use pin/plug gauges or a ball gauge, not calipers. Use micrometers to measure several barrel slugs.). If the cylinder throats are in fact only .0005" larger than the groove diameter of the barrel, I'd ream them out to .358"-.359". I've not had a leading problem when using lead bullets of the same diameter as the cylinder throats (in 5 revolvers) and I have used the same methods on PCed bullets (I size my PCed bullets to the same diameters as my cast lead bullets; cylinder throat diameter.)...

That's what I'd do...

[44man]

Paint on a boolit! I don't know. Paint does not stick good to lead. After a million posts I am not going there.
Hard boolits do not lead with fit. Soft boolits lead faster.

[TXCOONDOG]

Update:

Sent my cylinder to DougGuy and had him ream it to .358.5". Long story short, no more leading issues and my accuracy improved too.

Thanks for all the replies!

[swheeler]

I'm getting leading in my GP100 6" even though my cast boolits are powder coated and sized at 358" . The leading is taking place in the forcing cone and the first 1/2" of the rifling.

My alloy is WW + 2% tin with a BHN 17.

All my coatings past the hammer test with no flaking, etc.

My cylinder chamber measures at .356.5"

My velocities are around 1250 fps using blue dot.

Can the boolits still be to small with just enough room for the PC to get damaged causing the leading to occur ?

Any help or ideas are greatly appreciated.

I think those tight throats are the problem, have them opened up to .358+ and bullets at .358 good to go

[swheeler]

damn should have read last post!

[Black Chrome]

Glad you got the problem solved!

[gnostic]

Here's your problem, you're sizing with the cylinder....'My cylinder chamber measures at .356.5"

[Hogdaddy]

Here's your problem, you're sizing with the cylinder....'My cylinder chamber measures at .356.5"

Ya THINK :kidding:
H/D