The specs: 124 grain lrn Hi Tek coated bullets from ACME
3.9 grains Alliant Bullseye
M&P 9 pro 5"
Approximately 400 rounds fired

The problem: I started testing these particular bullets and powder around a month ago. Started with 10, shot them and was very happy with accuracy, and barrel appearance. So 50 more. No problems. Shot great. Then I loaded up and shot enough for an IDPA match (120+-). I was very pleased. Then comes last night and another match. The gun shot great and was accurate as always but when I got home I broke it down and checked the barrel. Lead lots of lead. Mostly in between one of the rifling and a little in another next to it (forgive my lack of the proper terminology) but the rest were pretty clean.

What happened? I've been seating and crimping separately. The only thing that I can come up with is maybe my crimp is too tight?! I did pull a couple and could see a line on the bullet where I'd actually squeezed the lead however the coating wasn't damaged.

Any thoughts are appreciated.

A bullet that is too small for your barrel (get it slugged to measure it) can cause lead from gas cutting from gas escaping around the bullet. The proper bullet size is about .001" to .002" larger than the barrel.
Many casting outfits can size your bullets accordingly.

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"He was kinda funny lookin'"

Yup. I've run powder coated 124gr. RN's from Lucky13 bullets and he sizes them to .357, most plated and FMJ's for 9mm are sized to .355 - .356. I've run these through many different 9's with no leading problems, even Glocks with the polygoogle rifling.

Fit is king, but I would be surprised if the HT was melting & allowing leading, even on a bullet slightly undersized. Are you sure it isn't coating? The only way the coating can come off is if it wasn't applied properly. Take an unloaded bullet & smash it flat with a hammer, coating should stick. Then wipe one with acetone, it should NOT wipe off. If it is coming off, it wasn't applied properly.
I am betting it's coating you are seeing. Does it brush out with a couple strokes of a brush? Everything you shoot leaves some fouling behind, it's just a matter of how hard it is to clean.

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NRA Cert. Inst. IDPA CSO

It's coating. I get it all the time with hi-tek coated (MBC) bullets. Not as bad as plain lead, but worse than anything copper or copper plated.

I could live with that, but I'm beginning to think it's harder to get off than plain lead.

It has nothing to do with crimp etc. It's just 'the way it is'. Hi tek coated bullets leave junk in your barrel...

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But then, what do I know?

I did smash it with a hammer and it didn't show any signs of coming off.
As far as what is sticking, I'm certain it is lead. I let the barrel soak overnight with hoppes copper and lead remover, no luck. Had to find some chore boy copper to get it out today.

I was hoping for a different solution than a sizing issue. The reason I went with the coated is to avoid this issue. I guess that slugging and shopping for someone who'll size for a decent price is the way to go. Or just go the plated route!

I have had excessive leading problems with MBC Hi Tek bullets in 30-30 when I've tried pushing them a bit too fast. If I keep 'em slow they shoot clean. Your load looks right in the ball park where you'd want to be, but perhaps try backing off a couple tenths and see what you get for leading.

You may have shaved one during the seating process.
That would give a start point for lead to build up

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it just needs more voltage

Do we assume they were at least 0.356"? Did you actually measure them? I do my osn ,but have never seen excessive fouling left behind. It cleans up with a hoppes soaked pat h & a few passes with a brush.

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NRA Cert. Inst. IDPA CSO

They do measure 0.356. I was sold on the coated bullets after getting some for my .357 mag and just for kicks, I pushed them fairly hard just to see what they'd take. No problems there at all. A slight red hue on the barrel that cleaned up nicely.

I was hoping for an economical load to shoot IDPA that I could settle on to make hundreds of with no worries. Now I've got a couple thousand coated lead that shot fine at first and now..... I'll continue to experiment, maybe lighten crimp, slow them down, or powder change. See if I can get a different result.

Has anything changed between the batch that didn't lead and the ones that do? Die adjustment, different brass, different lot of bullets...other??

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Trucks and guns.

Crimp changed due to concern that maybe I wasn't getting quite enough based on measurement. It's such a small difference between crimped and not (.001 or so) that I was questioning it.
The other possibility is that I tried to crimp and seat several rounds then pulled one to check it and it was scraping the coating off. I went back to seating and crimping separately but left those couple in the box. Would 2 or 3 cause leading that quickly? I assumed it takes time for it to build up but I wouldn't be here if I knew it all.

Are you chamfering and deburring the cases? I found I was getting some slight scrapeing of the coating. When I chamfered and deburred the cases, it stopped.

How much are you paying for those Acme bullets ? I buy 124 gr. FMJ and they are $88.00 per K delivered . No lead problems with FMJ .

That is a pretty good price for fmj. I picked these up for $62/ 1000. But if I can't figure them out, 2 cents per bullet isn't worth the hassle!

When a fouling problem occurs, measure. Measure the bullets. Slug and measure the barrel. When trouble shooting you need facts. If the coated bullet is larger than the groove diameter, then look someplace else, like crimp cutting the coating, or part of the coating scraped off during feeding...

It makes a difference whether or not the bullets are hardcast or not-- I believe. JMHO

One thing good about .355 and .356 dia. bullets is that they slide into a belled case with minimum problems.
ACME is said to be a standard .356 coated/lead cast, type bullet.

Now when you start to shove a .357 or a huge .358 dia. 9mm bullet into that case, you could start having problems with shaving the coatings off or damage, if not centered or seated too fast.

Then again, you might have a "Tight barrel".
Good luck with that.

Doesn't seem like that small change in crimp would do it. I was asking about the brass because I had some issues last year with thicker brass downsizing my projectiles when run through a factory crimp die. I just used thinner brass and the issue went away.

Definitely make sure you aren't shaving the coating off when seating.

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Trucks and guns.

It would be interesting to see how the same coated bullet in 38 super cal behaved. I can tell you that 130gr (plated) 38 super pills are my M&P pro's favorite fodder.

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Dave

This is a more likely problem, scraping the coating off. Make sure you bell enough. I like to seat & crimp separate for plated or led bullets. it can take only one uncoated bullet to start the leading issue, depends on how rough the bbl is. If it's a new gun, you might want to run 1000 jacketed, not plated, then clean the bbl really well. Then try the coated lead.

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NRA Cert. Inst. IDPA CSO

Where do you get such good prices on FMJ?

Precision Delta | Brass | Bullets | Ammo . You have to buy 2000 at a time to get these prices .
9mm 115 gr. FMJ are $83.00 per K delivered .
9mm 124 gr. FMJ are $88.00 per K delivered .