ACC
04-22-2023, 07:08 PM
I have read several posts here about an odd 9mm Lee truncated cone bullet, both regular and tumble lube versions going into a target sideways.
This also has happened to me in both my Smith & Wesson Model 59, which I have slugged the bore and it is .355 and my Taurus G2C which slugs at .356. This got me to thinking about the reason this only sparingly happens. It seems to only happen when I am working up a new load. Either a new powder or a new batch of my favorite W231.
This got me to start checking out items that may be causing this to happen.
I had the barrels of both my 9mm’s checked by a gunsmith friend of mine and his opinion was they were both fine.
Here is where it gets dicey. My regular Lee 125 grain truncated cone bullet was barely .3565. The other tumble lube dropped from the mold at .355.1. I measured ten different bullets with the same diameter.
The regular truncated I would push through a Lee sizing die that was .356 thinking this was the right thing to do. Was I wrong. After sizing the bullets they were coming out as .354! I don’t size the tumble lube bullet.
My gunsmith friend said that my light starting loads may not produce enough pressure to cause the bullet to fill the rifling. Another idea was that maybe my lead mix was too soft and they were stripping on the rifling. I think he may be on to something.
In the last two weeks I have done three things to fix this problem and I think I may have cured my problem.
I have changed my starting load with W231 from 3.8 grains to 4.0 grains. I have polished my Lee push through die to make it a true .356 and I upped my alloy to 13BHN.
After firing 250 rounds out of both guns I have not had any key holed bullets. Before in 250 rounds I would usually have one or two key holes.
Call me paranoid but this has gotten me to check all my Lee push through dies and all of them except one, the .358 which is .3595, are correct.
Here is what I have come up with:
Check your load. Make sure it’s not too light.
Check your bullet mold and sizer diameter.
Check you alloy to make sure it’s not stripping on the rifling.
I know this won’t affect a powder coated bullet, but it sure couldn’t hurt to check for best accuracy.
ACC
This also has happened to me in both my Smith & Wesson Model 59, which I have slugged the bore and it is .355 and my Taurus G2C which slugs at .356. This got me to thinking about the reason this only sparingly happens. It seems to only happen when I am working up a new load. Either a new powder or a new batch of my favorite W231.
This got me to start checking out items that may be causing this to happen.
I had the barrels of both my 9mm’s checked by a gunsmith friend of mine and his opinion was they were both fine.
Here is where it gets dicey. My regular Lee 125 grain truncated cone bullet was barely .3565. The other tumble lube dropped from the mold at .355.1. I measured ten different bullets with the same diameter.
The regular truncated I would push through a Lee sizing die that was .356 thinking this was the right thing to do. Was I wrong. After sizing the bullets they were coming out as .354! I don’t size the tumble lube bullet.
My gunsmith friend said that my light starting loads may not produce enough pressure to cause the bullet to fill the rifling. Another idea was that maybe my lead mix was too soft and they were stripping on the rifling. I think he may be on to something.
In the last two weeks I have done three things to fix this problem and I think I may have cured my problem.
I have changed my starting load with W231 from 3.8 grains to 4.0 grains. I have polished my Lee push through die to make it a true .356 and I upped my alloy to 13BHN.
After firing 250 rounds out of both guns I have not had any key holed bullets. Before in 250 rounds I would usually have one or two key holes.
Call me paranoid but this has gotten me to check all my Lee push through dies and all of them except one, the .358 which is .3595, are correct.
Here is what I have come up with:
Check your load. Make sure it’s not too light.
Check your bullet mold and sizer diameter.
Check you alloy to make sure it’s not stripping on the rifling.
I know this won’t affect a powder coated bullet, but it sure couldn’t hurt to check for best accuracy.
ACC