Number of PC coats to prevent leading

[Bill P.]

I have been powder coating cast bullets for a couple of years now and have had pretty good luck. With exception of the .40 s&w and 9mm I have to apply two coats of pc to keep from getting barrel leading. Is anyone else having similar results? Getting the same thing with multiple pistols the 9s are s&w m&P and glock 17 both slugged at .355 sizing to .357. the 40 is a s&w 2.0 slugged .4005 sized to .402. My alloy is running around 12-13 bhn pc is eastwood ford light blue and pbtp clear.

[edctexas]

I use an electrostatic spray gun and I only need one coat. I have never tried clear. It maybe different. I have used the eastwood ford light blue. I spray once from the front, and then rotate the tray 180 degrees. I then spray again. It goes into a convection oven. I measure the tray temp and the "free air temp". I try to keep the air close to 400. The tray always lags behind because of its relative mass.
One suggestion is to measure the boolit after one coat. Mine typically run .002 over the boolit size before coating.

Hope that helps EDC

[bmortell]

catching one of the boolits in water might show if theres some kind of problem

[Black Jaque Janaviac]

I am not sure what you meant. Are your 9s and 40s working well with only 1 coat and all other calibers need 2 coats?

[Bill P.]

No the 9s and the .40 are the calibers that need 2 coats. This has been puzzling me for over a year now. I am able to do well with .45 acp .44 mag .357 mag with just 1 coat. First I thought the cases where sizing down the bullets but I have M expanding dies and the cases are only swaging down the bullets .0003-.0005 at the most.

[Rcmaveric]

The Lee 356 124 R2 leads all my guns no matter how many times I coat them. They work great lubed though. On the other hand, the Lee 356-124 TL works great in all my guns off one coat.

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[jessdigs]

Are you using a noe expander or m die to expand the case enough. If the base is getting swaged down it would cause leading.
Once I started expanding the cases in 9mm my minor leading went away.

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[Dragonheart]

Based on your slugged barrel sizes the first thing I would do is size the 9mm to .356" and the 40 to .401". All a bullet has to do is to fully engage the rifling and provide a seal for the gases. Once it accomplishes that then an oversized bullet is just spiking pressure to size down and move more metal. Some say oversizing increases accuracy, but I have yet to see any actual tests to prove that out. In my own limited Ransom Rest testing I have found oversizing bullets actually increased group size with identical loads. Sizing may solve your issue.

I single coat all my handgun bullets without issue, so my next question is your powder a quality powder? Are you absolutely sure your bullets have not been contaminated? A water drop to cool is a good way to contaminate bullets. Is the first coat a complete coverage and has it been properly cured. Meaning can you confirm absolutely the bullets surface came to 400F. degrees and stayed there for at least 10 minutes?

[cwlongshot]

Countless thousands of forties theu three different guns in last two years. Never a hint of leading. Im shooting 145 & 180g at 900-1300 fps. Thru Glock and aftermarket barrels.

Either your pc isnt cured or maybe bad/ contaminated powder.

[Bill P.]

I started sizing to .356 and .401 and went larger because of light leading when I went a little larger it may have made a difference but not much. Powder is east wood and PBTP. As far as bullets reaching 400 degrees I cant be certain I just preheat to 400 put them in for 20 min and take them out. Oh yeah and they pass the smash test as well. Thanks for the help guys.

[cwlongshot]

[Bill P.]

Cwlongshot at what temp and how long do you bake? The bullets on the right look like they survived very well. When I pull mine out of the ground they look like the ones on the left.

[stubshaft]

I bake mine at 400 deg. for 25 minutes and all of the boolits I have recovered look like the ones pictured on the right.

[Dragonheart]

I started sizing to .356 and .401 and went larger because of light leading when I went a little larger it may have made a difference but not much. Powder is east wood and PBTP. As far as bullets reaching 400 degrees I cant be certain I just preheat to 400 put them in for 20 min and take them out. Oh yeah and they pass the smash test as well. Thanks for the help guys.

How do you know your oven is actually at 400 degrees because an oven thermostat/dial is worthless? The Smash Test is almost worthless. Bullets cooked at 200 degrees will pase the smash test as that only tells you the powder bonded. My best guess is your bullets are not cured.

[Bill P.]

I used a thermostat to check the temp was at 400 in the oven. But that doesn't mean my bullet temp was up to 400. And what is weird is why am I only having trouble with 9mm and .40. Only difference I can think of is they have a much faster barrel twist.

[cwlongshot]

Yup 400/20 as specified by most powders. But as mentioned its 20 AFTER powder flow so the actual bake time varies.

CW

[Hick]

I use one coat of Smoke's clear (400 degrees for 15 minutes). I've recovered bullets fired at over 2000 fps with no visible damage to the coating and no leading. In my pistols, including 9mm, I also see no leading at all.

[Dragonheart]

Yup 400/20 as specified by most powders. But as mentioned its 20 AFTER powder flow so the actual bake time varies.

CW

All the specs I have read from the actual powder manufactures is 400F for 10 minutes after the substrate comes to temp for most powders. The only seller that mentions flow is Eastwood and they are not a powder manufacturer they are a reseller. Assigning an artribury number after powder flow can end up with undercured bullets because timing after flow does not take into account a changing dynamic load.

[Dragonheart]

I used a thermostat to check the temp was at 400 in the oven. But that doesn't mean my bullet temp was up to 400. And what is weird is why am I only having trouble with 9mm and .40. Only difference I can think of is they have a much faster barrel twist.

I would suggest getting a Glass Taylor Oven Guide Thermometer (about $12 at Amazon) and put it in the oven where you can read it through the glass door. This thermometer is accurate and reads immediately. It will allow you to check your oven to see if it is getting to 400 and if the oven can stabilize at that temp.

The polymer jacket of a properly coated and cured PB bullet can withstand over 50K pounds per square inch of chamber pressure and can resist the tork spin up of velocities of 3500+ feet per second. Others including myself are shooting PC bullets without issue, so it has to be your bullets. If you confirm the cure and the problem remains I would suspect the powder. You may also have a polymer build up in these barrels that needs cleaning.

[cwlongshot]

All the specs I have read from the actual powder manufactures is 400F for 10 minutes after the substrate comes to temp for most powders. The only seller that mentions flow is Eastwood and they are not a powder manufacturer they are a reseller. Assigning an artribury number after powder flow can end up with undercured bullets because timing after flow does not take into account a changing dynamic load.

What are you saying to me here?

CW