leading

[greyling22]

so I've been struggling a bit with leading in my 9mm. I'm pushing a pretty hard 124grn .356 lead bullet about 950 fps with liquid alox as lube. (bullet is dropping a true .356, and I slugged the bore out to .356 as well) I get some leading that is following the rifling down the barrel. According this http://www.lasc.us/Fryxell_Book_Chapter_7_Leading.htm

" Streaks, following the rifling: If the leading is seen to "follow the rifling" (i.e. streaks that twist down the barrel in close association with the rifling grooves), then this is a tell-tale sign that the bullet is cast too hard and failing to obturate. Obturation is usually thought of as a plastic deformation that swells the bullet's diameter, but it also leads to a back-filling of engraving defects along the trailing edge of the land. If the bullet is cast too hard to obturate, these defects will not be back-filled and gas-cutting will take place through these voids, following the trailing edge of that particular land. This effect can be mitigated somewhat through judicious choice of lube, but lube by itself can only do so much. The real solution here is to go with a softer bullet and a better lube."

you cast bullet wizards, does that seem right to you? if so, I'll try a softer bullet, double coat with alox, and push it a little faster. or some combination of the above. I'm using 4.4 grns of 3n37 as powder. I started out using red dot, but I was getting keyholing, so I went with a slower powder/harder bullet combo and the issue went away.

 

[918v]

Matching the bullet to the rifling does not stop leading. There is the freebore, and lead alloy hardness, and lube, and the power and its properties.

I suggest you chambercast your barrel, match the bullet to the freebore, ditch the alox and lube with Javalina, and use a softer alloy that will obturate the freebore upon ignition.

 

[murf]

is your bullet flat-based, or bevel-based?

increase the velocity (pressure) and see if that helps (within saami specs, of course).

good luck.

murf

 

[LiveLife]

If the groove diameter of the barrel is .356", shouldn't your bullet be sized to .357".

I think bullet-to-barrel fit is key to reducing/eliminating leading followed by proper deformation of the bullet base (obturation) as the result of lead alloy hardness and amount of powder charge used. Perhaps size the bullet to .357"?

124grn .356 lead bullet about 950 fps with liquid alox as lube ... using 4.4 grns of 3n37 as powder.

 

[Blue68f100]

Pushing it that hard you may have issues no matter what you do. But looking at the table BDS posted you may be too light. Some powder like TG when used with lead will always cause leading, it burns too HOT for lead bullets. Use a lower temp powder like WST and see if it helps.

Bullet fit to barrel is key on limiting leading. Your bullet size should be 0.001" over what your barrel slugs.

 

[LiveLife]

3N37 is a slow burn rate powder on par with Silhouette, AutoComp, HS-6 and AA #5.

My experience with HS-6, WSF, AutoComp and other slower burn rate powders is that you need to be using high range load data before you have consistent chamber pressures. Although your loads chrono at 950 fps, you may not be generating enough chamber pressures to deform the bullet base (I am assuming you are casting wheel weights?) to obturate and especially with .356" sizing of the bullet for .356" barrel, you are probably getting gas cutting which explains the type of leading you are experiencing.

looking at the table BDS posted you may be too light.

I think European 9mm loads as Vihtavuori load data indicates tends to be loaded hotter on par with "American +P" loads (curious what the PSI measurements are of those loads as published velocities are out of 4" barrels ). 4.4 gr of 3N37 just may not be producing enough initial chamber pressure pulse to expand the bullet base to seal the high pressure gas. I think proper sizing of .357" and a higher powder charge would decrease the leading and personally would use a faster burning powder if velocities are kept below 1000 fps. (I think 3N37 would be fine for use with jacketed bullet at jacketed velocities).

 

[snuffy]

bullet is dropping a true .356, and I slugged the bore out to .356 as well

What bullet is this^^?

It sounds like greyling is lubing/sizing an as-cast bullet. Since it drops @ .356, it can't be sized BIGGER! Also, there's nothing wrong with LLA,(Lee Liquid Alox). If the bullet was sized correctly, AND it was pushed hard with a faster burn rate powder, it would shoot without leading.

A faster burn rate powder would give the base of the bullet a hard kick, starting the obturation process.

Adding a bit of tin to the alloy might increase the as-cast diameter, as well as making it a bit harder. Then, sizing to .357 might allow the use of the slower burn rate powder.

 

[LiveLife]

greyling22, are you casting the bullets yourself or are you using commercial cast bullets?

If you are using commercial cast bullets, you can order them sized at .357".

 

[armoredman]

Interesting. My wheel weight Lee 124 bullets drop at .360 and I size them down to .356 with a Lee push through sizer, lube either hard lube with a homemade alox/beeswax composition or Lee Liquid Alox. Pushed with Accurate Arms #7 I get very little leading in any pistol they are used it, even when Accurate Arms revised their data and one load now proves to be +P!
Well, a cast 9mm slug at an average 1164 FPS is a bit warm...
Do you have other powders to try? Burn rate might cause some of this, as mentioned above.

 

[Walkalong]

Pushing a 124 Gr 9MM bullet to 950 FPS is not pushing it "hard", which is probably why 918v suggested a softer alloy. The other option is to push it harder and see if the leading stops. Plus you need to size to at least .357 if the bore slugs at .356.

 

[greyling22]

I just loaded up batches of 20 that get progressively hotter and see what that does. I'll also cast a few softer bullets. I'm using a mixture of mostly wheel weights with a little linotype tossed in, then water quenched.

this is the mold. http://www.midwayusa.com/product/340779/lee-6-cavity-bullet-mold-tl356-124-tc-9mm-luger-38-super-380-acp-356-diameter-124-grain-tumble-lube-truncated-cone

I also tried a few .358 diameter 125 grn bullets, same lead alloy and powder charge. they were leading too, though not quite as bad. so I sort of ruled out undersized bullets. sort of.

I'm almost out of the 3n37, and I have w231, titegroup, n320, blue dot, #5, and a few others. I tend to buy whatever other people are getting rid of or had when they died.

 

[918v]

I can tell you that 3.7-4.1 grains of 231 under a .358" 125gr TC would not lead in a Beretta. It had a .359" throat. I think your load is too light pressurewise to obturate the base of the bullet. Go with a faster powder.

 

[LiveLife]

Same here. I am using .356" sized 18 BHN Missouri 125 RN and 3.8 - 4.2 gr charges won't lead in various pistols/barrels.

Even faster burning Promo at 4.0 gr with the same bullet won't lead the barrels.

 

[LiveLife]

I'm almost out of the 3n37, and I have w231, titegroup, n320, blue dot, #5, and a few others. I tend to buy whatever other people are getting rid of or had when they died.

Another thought.

Do you know how old some of those powders are when you get them?

If stored tightly sealed under proper temperatures, I tend to consider 10 years a good timeframe to use up my powders (most of time, I use them up within 3-5 years).

 

[Hondo 60]

Had my 9mil out to the range the other day.
After 47 rd of 124gr LRN, (with 4.1 gr of Tite Group) it suddenly refused to chamber the last 3 rounds.

When I got home I could see the leading using one of those cheap bore lights.
A scrub with Hoppes # 9 & another few turns with a mop wrapped by a copper strand from a chorboy & it was clean as a whistle.
Those last 3 rounds chambered just fine.

I think I'm gonna stick with plated/jacketed in that gun.

 

[Walkalong]

mostly wheel weights with a little linotype tossed in, then water quenched.

That's a pretty hard bullet. Much harder than you need for the pressure/velocity you shot them at.

 

[greyling22]

so general consensus is that the article was right, my bullet is too hard?

 

[LiveLife]

I think so, and probably not enough powder charge or too slow of powder or combination of all, including the sizing of the bullet.

My Taurus PT145's barrel is oversized like around .456"+. When I shot 18 BHN Missouri 200 gr SWC (IDP #1), it smeared leading around the leade and leaded down the rifling. I shot it with different powders and charges and it didn't matter and accuracy sucked bad.

When I used the softer 12 BHN 200 gr SWC (Bullseye #1), .452" sized bullet base deformed enough to seal with the oversized barrel with different powders/charges like 5.0 gr of W231/HP-38 and even light 4.0 gr charge of Promo to produce very accurate shot groups and no leading.

 

[earplug]

Are you using a Lee Factory crimp die? I and other people have had problems like yours due to the bullet getting re-sized by this type of die. It irons out any case bulge but squeezes the bullet undersized at the same time.
If not, I'd stop using the Linotype and go soft.

 

[ArchAngelCD]

I'm almost out of the 3n37, and I have w231, titegroup, n320, blue dot, #5, and a few others. I tend to buy whatever other people are getting rid of or had when they died.

I use W231 for 124/125gr lead bullet for my 9mm ammo and it works very well for me. A charge weight of between 4.4gr and 4.8gr will do very well. I make light ammo with the 4.4gr load and it cycles well for me.

BUT, I would soften up that alloy to some were near 12 BHN if I were you or your leading problem will continue IMO.

 

[Cherokee]

Bullet too hard for that velocity. Kick up the power. Size 357 would probably be better for your barrel if its really 356. If casting your own, soften up the alloy some.

 

[greyling22]

Well, I cranked up the velocity some today, and still had leading issues. I'm going to change powders, cast a softer bullet, and double lube the bullets and see what happens.

earplug, I was using the FCD, but I stopped a few months ago. nothing changed as far as leading or accuracy.

Bds, there is no telling how old some of this powder is. when was the last time you heard of trap 14? red dot sold in little metal cube cans? the 3n37 is fairly new though. it came from a different old dead guy.

Interestingly enough, I am using the same alloy in my 357, using a 125grn .358 bullet over some trap 14 (somewhere in between green and blue dot on the burn rate) and I get very little leading, and that stayed near the rear of the barrel.

 

[greyling22]

So I tried a few more loads today. Since it seemed like I was using too slow a powder, hard a bullet, and too light a load, I tried going the other direction. I was using a pretty soft bullet, (can almost scratch it with a fingernail) and HS-6 and some acc #5. I was trying to stick to the start loads and not load light. I did not heavily lube with alox. I did not use the lee FCD.

4.5 grains of HS6 shot ok, but was leading.
5 grns hs6 shot ok, but was leading.
5.5 grns started keyholing, and leading the whole length of the barrel.

5.2 through 5.6 grains of #5 was keyholing and leading.

Did I go too soft with my bullet this time? or do I need to back my velocities down further? This is getting frustrating. It's the only blasted gun I can't get a load going for.

 

[gahunter12]

Have you tried WST or maybe W231? I have been loading lead in 40s&w and 45acp with WST and W231 for 40s&w, and 18BHN cast bullets without any leading. All my bullets are measuring .001 over my barrel diameter. I tried pushing my .40 loads to the max lead data with out any signs of leading.

 

[Walkalong]

I do not think you went too soft, but you are still using medium slow powders loaded down. Try some faster powder to get pressure up and still keep velocity down.

WST is a good suggestion, or W-231 as well. It should work.