A Balanced 357 Magnum Load

[LeverGunner]

I developed a 357 Magnum load using the RCBS 38-150-SWC - a plain based bullet, and 16.8 grains W296. The bullets are cast from wheel weights + 2% tin, sized .357, and lubed with White Label 50/50.

This is near maximum out of the book, and of course is a full power 357 Magnum load. I've not tested it thoroughly for accuracy across a wide range of firearms, but so far it's been accurate in both a GP100 and a Smith & Wesson 686, and my buddies R92 (only a limited amount shot there due to bulged cases).

Here is the interesting part. Both of those aforementioned revolvers have issues with leading. The GP100 would lead with every load I tried. 38 specials with bullseye and unique to mid-level magnums with unique, several bullets and bullet lubes, several sizes, several alloys, even gas checked bullets! It had larger throats than groove measurements. I recut the forcing cone to 11° and firelapped it. I had only the faintest constriction at the threads when I paused lapping. I sold that gun a while back when things got tight.

The 686 leads with plain based 38 specials so far. I've not done a lot of testing with it yet, so I can't say much about it. I don't remember if I've slugged it or not.

Anyways, I was out shooting it the other day, it had been shot with some 38's I was testing previously and I had leading at the forcing cone and down the first 1/2 of the bore. The aforementioned load shot clean, the bore is spotless.

The only thing I can figure is the load is perfectly balanced between alloy, lubricant, and pressure.

Anyone else have a take on it?

[tj3006]

I can't call myself a real expert on such things,
I have never had a revolver that leaded with 38 specials. It seems like until you have slugged the bore, experimenting with components is putting the cart before the horse.
...tj

[Fowler]

I shoot that bullet a lot, its probably my favorite 38 cal bullet. Sizing to .357" dia strikes me as a touch small, I typically size .358" but then most of my 38/.357 guns have .358" throats. Undersized bullets allow gases to get around the base and burn the sides of the bullet base leaving lead in the bore. or so the theory goes. You really need to size the throats with machinist pin gages to be certain (any machine shop will have a set and can measure the throats in a minute or two).

Your lube might also be part of it, I have never used White Label products so I have no insight there, but it may be happier at the higher velocities but I just don't know. I used LBT blue soft pretty much exclusively since I started because everyone said it was the best and I believed them.

The other thing I have gone to over the last few years almost exclusively is I have been powder coating my bullets and it has really helped reduce leading at all velocities.

But I think you need to start by checking the bore sizes and then sizing to match...

[2 Dogs]

Jun 17, 2023 1:01:18 GMT -5 LeverGunner said:

I developed a 357 Magnum load using the RCBS 38-150-SWC - a plain based bullet, and 16.8 grains W296. The bullets are cast from wheel weights + 2% tin, sized .357, and lubed with White Label 50/50.

This is near maximum out of the book, and of course is a full power 357 Magnum load. I've not tested it thoroughly for accuracy across a wide range of firearms, but so far it's been accurate in both a GP100 and a Smith & Wesson 686, and my buddies R92 (only a limited amount shot there due to bulged cases).

Here is the interesting part. Both of those aforementioned revolvers have issues with leading. The GP100 would lead with every load I tried. 38 specials with bullseye and unique to mid-level magnums with unique, several bullets and bullet lubes, several sizes, several alloys, even gas checked bullets! It had larger throats than groove measurements. I recut the forcing cone to 11° and firelapped it. I had only the faintest constriction at the threads when I paused lapping. I sold that gun a while back when things got tight.

The 686 leads with plain based 38 specials so far. I've not done a lot of testing with it yet, so I can't say much about it. I don't remember if I've slugged it or not.

Anyways, I was out shooting it the other day, it had been shot with some 38's I was testing previously and I had leading at the forcing cone and down the first 1/2 of the bore. The aforementioned load shot clean, the bore is spotless.

The only thing I can figure is the load is perfectly balanced between alloy, lubricant, and pressure.

Anyone else have a take on it?

Here’s a 357 thread:https://singleactions.proboards.com/thread/35654/357?page=1

[jeffh]

Jun 17, 2023 1:01:18 GMT -5 LeverGunner said:

....

Anyone else have a take on it?

With no other information to go on, I'd lean toward the possibility of a real magnum load deforming the bullet enough to plug all the little holes where lands meet grooves and mitigating blow-by gasses.

That would mean that the lighter loads might need fatter bullets, but like I said - with no other information...

Glad Fermin posted that other thread too.  I got busy and lost track of it and then forgot before getting through it.  I've been messing with the 357 extensively for a bit over a decade after several previous decades of looking down my nose at it.  My interest is in a Revolver/Carbine application with a need for a "universal load" in addition to a few specialized ones.