The leading mystery has finally been solved!

[Gunslinger]

These last few months I’ve had problems finding a load for my 9mm that wouldn’t lead the barrel. At first I thought it was the primers, but you guys said the alloy was probably too soft. I recently got it measured and it showed a BNH of 10, so you were right, it was too soft. I moved on to make an alloy of 50/50 range lead/ww thinking this would solve it. My range lead contains a good amount of cast and runs at BNH 9 which I think is pretty good for range lead. This alloy leaded the barrel just as the previous. Okay then… not hard enough. I cast a new batch and water quenched them and measured them to BNH 18. I was 100% certain that my leading days were over… but once again I was wrong, the loads were nearly as bad as the other ones.

I took on my thinking hat (a real ugly fisherman’s hat) and started eliminating all possibilities.

- Primers
- Lube
- Different COL
- Different bullet styles of the same alloys.
- Different powders Vv N320, Vv N340 and Bullseye
- Heat treating the 3 above mentioned alloys
- A fourth alloy: 3-1 WW – Lino


NOTHING helped. So as you can imagine this young caster was in despair. The BNH 10 boolits work like a charm in 38 special, so I knew I wasn’t completely clueless. But as I’d run out of possibilities I called an acquaintance of mine who has been casting for longer than I have been alive. I had prepared a whole speech explaining all the thing I’d tried but before I had a chance to start he asked me: “What kind of brass do you use”?? Taken completely by surprise I mumbled “ehhh Magtech brass”?! “Ohh you need to stop using those at once” he replied. I swear I could have cried like a school girl. I’ve been collecting Magtech brass for the last 5 years and I probably have in excess of 8000 pieces.

Anyways I did as he instructed and dismantled a few cartridges. The brass measures between 0.011” – 0.012 at the case mouth as they should according to SAAMI, but longer down where the bullet is seated they measure 0.015” – 0.017” so you can imagine what happens to the boolits when loaded. I measured them too…. 0.354 – 0.355 at the base! My barrel is 0.356 and I size to 0.357.

That being said, I am able to fire 200 rounds through the gun without accuracy suffering. And removing lead with a bronze brush and Break Free is a piece of cake… so I’ve decided to live with a leaded bore.

Why I had regarded the brass as being sacred ground I really can’t answer. At least now I know how to go about things the next time I experience leading. Lesson learned for this green caster ;)

[geargnasher]

Glad you finally identified the problem. Hope you have some hair left!

I ran into the same thing trying to work up .45 acp with 250-grain 454190s sized to .452" (correct for my gun). I had to seat them for a max OAL of 1.251" and that put them about .030" past the point where the case starts to thicken. Guess what? They leaded like crazy until I put MY ugly thinking cap on (a big straw sombrero!) and started hacksawing brass down the middle. I found that W-W headstamped cases have thinner walls and stay thinner toward the case head, so I could seat the boolits as deeply as needed with reduced leading. Not perfect, but much better than with "good" correctly dimensioned brass.

Gear

[truckmsl]

I would think that you could use your Magtech brass without problems if you use a harder alloy, or just water quench what you're presently using. Almost any brass will size down a soft, oversize boolit.

[Bret4207]

Fit is King. You ALWAYS start with fit above all else. In your case the Magtech may be workable. Check some fired cases loaded to at least a mid range level so there's some case expansion. Check and see if it measures the same as the other FL sized brass you have. Two ways of working with this- If the brass expands enough not to mutilate the boolit then see if you can partially size it and still get functioning without damaging the boolit. If not, you can inside ream the cases a bit to thin the walls and still use the brass.

A harder alloy MIGHT work, but you're already at 18 Bhn and I'm not sure how much harder you realistically (expense/trouble-wise) you want to go.

[truckmsl]

gunslinger - I've found that with some high pressure calibers I need to use 100% water cooled wheel weights rather than 50/50 to prevent leading. Sure would be nice to find a way to use all that magtech brass - I'd keep trying to find a way, even if just for light target loads.

[GabbyM]

How about a Lyman M die?
The 9mm I have is .353" on the long first step. then .357" for .085" long then the mouth flare step. Or maybe a 357 pistol expander plug in whatever die you have. You can buy custom expander plugs or anyone with a lathe can make one.

If you're trying to use those 147 grain bullets all I can say is I gave up on that after my first box years ago.

I'd of thought your BHN #18 boolits would have stretched the case out maintaining bullet diameter.
But I guess not.

[runfiverun]

use a lighter boolit that don't seat as deep.

[leftiye]

Get a longer (and maybe larger) expander "ball". Should stop the cases from sizing the boolits down. (now if they only will still chamber!) If they won't chamber, you could try neck turning them.

[captaint]

Hey Slinger - You're losing your "green". Ain't it fun?? As you now know, always look at boolit diameter. Be suspicious, very suspicious!!! Enjoy, Mike