Can Over Sized Boolits Cause Leading?

[Utah Shooter]

Ok searching for a couple of days not and not finding anything.

The list:

CZ P10c barrel slugged at .356-.3565 and coal @ 1.100 because boolit will not chamber if it is longer.
Mihec's 130 2r boolit sized to .358 with Hi-Tec coating, yes passed the rub test.
After sizing baked at 400 for 30 minutes and water dropped. Also allowed to harden for 2 and a half weeks before reloading.
Pulled boolit after seating and crimped measured at .358 without any shavings.
3.8 gr of HP-38

Getting horrible leading in the last half of the barrel. What am I missing?

[Tom W.]

If I read your post right your bullets are undersized...... which will cause leading.

If I missed something just ignore the post.

[Tom W.]

By .007?

[tazman]

Are you sure it is .365 and not .355?
Is your barrel rough? Does it have some machine marks on the rifling?
If so, the coating may be getting stripped in the barrel.
If you can recover some of the boolits, it would be helpful to see what the sides looked like after passing through the barrel. If there was any skidding going on it would show on the recovered boolits.

[Utah Shooter]

duh me. .358 boolit in a .356 - .3565 barrel. Sorry been a long day.

[tazman]

With the barrel .356 and the boolit .358, the sizing should not be a problem.
It is also possible the coating is being stripped at the front of the chamber if the throat is sharp and the rifling very abrupt.

[Tom_in_AZ]

With the barrel .356 and the boolit .358, the sizing should not be a problem.
It is also possible the coating is being stripped at the front of the chamber if the throat is sharp and the rifling very abrupt.

Two thousandths over is good. That’s probably not causing the issue. Barrel bulges, irregularities, etc could be the problem.


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[Tom W.]

We all have those kind of days....

[Michael J. Spangler]

How did the coating look after baking that long?
I would do a smash test to make sure the coating didn’t get brittle.
I’ve found that baking for 10 minutes on the last coat and water dropping was sufficient for hardening. Given a week for age of course.

[Tom_in_AZ]

How did the coating look after baking that long?
I would do a smash test to make sure the coating didn’t get brittle.
I’ve found that baking for 10 minutes on the last coat and water dropping was sufficient for hardening. Given a week for age of course.

Good point. If the coating is brittle, that could be an issue. Smash test time.


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[Utah Shooter]

Good point. If the coating is brittle, that could be an issue. Smash test time.


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Ahh. Something I didn't do. Perhaps baked too long?

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[Rcmaveric]

Problem solved. Good call Mr. Spangler. +1 And you get extra credit for solving the problem with a big hammer. Nothing like a percussive test.... percussive maintenance is what we call it at work.

[tazman]

When in doubt, get a bigger hammer.

[243winxb]

At .002" over groove diameter, where do you think that coating is going to go when the barrel sizes the bullet down and rubs it all off? After the coating is off, about 1/2 way down the barrel, no lube, its going to lead.

Just my way of thinking.

[ioon44]

Ahh. Something I didn't do. Perhaps baked too long?

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Baking too long will not cause the coating to fail, the first coat not being dry or too thick before baking will cause failure of the smash test.

You didn't state what alloy you are using, I have great results with 14 to 16 BHN for 9 mm bullets and don't need to mess with water dropping.

Barrel bulges, irregularities, short sharp forcing cone can cause problems with coated bullets also as others have posted.

[ioon44]

At .002" over groove diameter, where do you think that coating is going to go when the barrel sizes the bullet down and rubs it all off? After the coating is off, about 1/2 way down the barrel, no lube, its going to lead.

Just my way of thinking.

I shoot Hi-Tek coated .002" over grove diameter with out any leading, when the coating is applied properly it bonds to the lead and sizes down with the bullet.

I have recovered my bullets from a rubber mulch bullet trap and the coating is still 100%.

[Michael J. Spangler]

I shoot Hi-Tek coated .002" over grove diameter with out any leading, when the coating is applied properly it bonds to the lead and sizes down with the bullet.

I have recovered my bullets from a rubber mulch bullet trap and the coating is still 100%.

Same here.

Although I have notices that baking longer can cause brittleness.
I was the one who cast and coated those bullets for him and I'm very careful about a wipe and smash test on every bake I do. I'm not saying I haven't made mistakes in my life but I'm going to bet it's the half hour bake after already being baked with 3 thin coats.

[mdi]

I think I would eliminate the water dropping. One purpose of PCing is to eliminate leading and extra hardness isn't needed for that. If hard bullets are needed, for some reason, I'd go with hard alloy and eliminate extra processes; water dropping and waiting period.

FWIW; for me and many others it's easy to get wrapped up in a process and take it to near infinity; eg, overthinking. I cast for prolly 12 years using nothing but wheel weight alloy or it's BHN equivalent and managed to eliminate most leading in all my handguns, 9mm through 44 Magnum. But, the ideas I had to maintain were K.I.S.S. and when working out problems use standard troubleshooting methods (research and change one item at a time, step by step). I now have bullets/loads that will shoot without much, very little if any leading and basically it's bullet size, then lube then powder. I have 3, 9mms and my 125 gr. Lee RNFP bullets, sized to fit the particular gun (three sizes 356", "357", and .358"+ and .358"+ would prolly work in all three), using a good lube (mostly C-Red), shoot accurately and very close to zero leading...

[Michael J. Spangler]

I have found the use for water dropping in 9mm is to counter the neck tension from the undersized expanders. If you’re running single stage it’s easy to swap out expanders but progressive you can’t always find a proper funnel to actuate the powder and expand properly.
Softer bullets squish down under the neck tension. Harder bullets can counter than and Elena Nate the need for a customer expander

[gwpercle]

Try not cooking and quenching the coated boolits. Just skip that step and load them after coating.

Hardness is way over rated. Proper fit matters more.
I mix COWW's and lead 50-50 , cast them and drop on a dry towel , air cool and size to .357 and lube with Lithi-Bee . That's it .
Loaded in several 9mm's with several different powders .....NO leading in any . Not one.
Your boolits might be too hard....the cooked on coating isn't working....from your description I would say you are running out of lubricant...but you don't have any lube, must be the cooked coating is failing.
Gary