Minor leading with Cast 9mm

[Fizz]

Lee 9mm ~124 Gr TL boolits, 4.1 grains Unique. 1.080 OAL. Lubed with Alox (just enough to barely darken the lead when dry... still smokey as hell). .001 over slug. 6% Anti, 2%tin water quenched. Boolits were 'aged' about 4 weeks.

I shot about 150 of these yesterday and noticed some light leading in the grooves of my EMP (3 in barrel), but only in the last 1.25 inches before the muzzle. Before that is pristine/lead free.

Curious what this means? The leading came out after working with a bore brush (snake couldn't touch the stuff) but it's more effort than I'd like if there's something I can do to just stop it from happening at all.

[Germz]

even with powder coating boolits I get very minor leading, but significantly less than alox lube and my alloy.

[thenodnarb]

Haven't shot any lead 9mm yet, but my .40 I shot yesterday and got absolutely no leading with powder coated bullets. I spray it on so its a pretty consistent and thick coating(maybe .001 total).
Of course my velocity is probably a lot less than your 9. Only about 850 so far.
I also shot my 303 british with powder coated bullets. Same process, same alloy(wheel weight) with a gas check. Pushed them at 2250 fps and no leading.

I'm no expert, but leading at the end of the barrel is indicative of something. vs leading at the beginning or throughout. I believe it indicates the lube is failing.

I hate alox. I still get leading with it and abandoned it pretty quickly.
When I don't powder coat, I use my own pan lube I made with what I have laying around. an equal mixture of bees wax and parrafin, with another 10% of crisco or olive oil added in to soften it up. I have not had any leading with this mixture yet and I have pushed those same .303 bullets to a round 1800 FPS with that lube and gas check. I mainly use it for .45 and .38spl though.

Bottom line, change your lube. or start powder coating.

[BigBronco]

Yep sounds like lube fail. I as well hate alox. I would think gas cutting would lead more of the barrel that the last bit. Out of curiosity did you slug and measure the bore?

[J-cat]

What is the throat diameter of your chamber? Your bullet may be .001" over your bore but too small for your throat.

[Bastard]

isn't unique smokey as hell anyway, and yes the lube will smoke regardless.

how fast are you pushing it?

as for cleaning it, just run a chore boy down the barrel - works like a charm.

[Fizz]

What is the throat diameter of your chamber? Your bullet may be .001" over your bore but too small for your throat.

Can you elaborate on your thought process on this? I'm not sure I understand what you mean.

[Fizz]

isn't unique smokey as hell anyway, and yes the lube will smoke regardless.

how fast are you pushing it?

as for cleaning it, just run a chore boy down the barrel - works like a charm.

No Chrono so I don't know. I am far below the maximum though. It cycles 100% and puts holes in the general vicinity of where I want them without pressure signs, so I haven't investigated the velocity too much.

[Fizz]

Yep sounds like lube fail. I as well hate alox. I would think gas cutting would lead more of the barrel that the last bit. Out of curiosity did you slug and measure the bore?

.001 over on the bullets. That said I'm thinking I should do it again just to be sure.

[thenodnarb]

Can you elaborate on your thought process on this? I'm not sure I understand what you mean.

You can sometimes go a few thousandths over groove diameter depending on your throat. However I think your leading pattern doesn't indicate that an undersized bullet is your problem. .001 over groove is fine.

[J-cat]

Can you elaborate on your thought process on this? I'm not sure I understand what you mean.

Your chamber has a throat. It is the area just before the rifling starts. These measure anywhere from .357" to .360" depending on the manufacturer. If your bullet is undersize for the throat, just like in a revolver, it will lead.

[Goesfaster]

While reading the Lyman cast manual I remember that leading near the end of the barrel means not enough or not correct lube. Hope that helps.

[Fizz]

Your chamber has a throat. It is the area just before the rifling starts. These measure anywhere from .357" to .360" depending on the manufacturer. If your bullet is undersize for the throat, just like in a revolver, it will lead.

Right but I'm leading at the muzzle end?

[Fizz]

While reading the Lyman cast manual I remember that leading near the end of the barrel means not enough or not correct lube. Hope that helps.

May very well be. I used a lot less than my first batch.

[J-cat]

Right but I'm leading at the muzzle end?

Your right. Maybe two coats of alox instead of one next time?