Setting up cast boolits in Smith 57-1 and 58

[BK7saum]

Slugged barrel and throats in the 57-1. Groove appears to be right at 0.410 as measured with micrometer and a feeler gauge wrapped around the slug. The cylinder throats all measured 0.4113-0.4115 and slightly oval by 0.0002" or so. The oval part seemed odd but all 6 measured the same.
There might be a slight 0.0005 thread choke in the barrel but cant really tell.
I have been getting a little leading with a 50/50 alloy sized . The boolits are measuring 0.4105 from a lee mold and are lubed with Ben's red in a 0.411 die.
Leading is occurring in the breech end of the barrel. Since my boolits are slightly undersized to the throats, am I getting gas cutting that is leaving lead just in front of the forcing cone? This is a light-medium load of unique.
I'm waiting on the 412640 mold right now. Yippee. And will be sizing to a true 0.411" . Or should I get a 0.412" lube die and size them larger than the throats.

The nickeled 58 throats measure 0.4117 plus or minus a couple of ten thousandths. And I definitely have a slight thread choke in that one. Once I can cast some larger 0.412-3 boolits to better match the throats, I hope to see some improvement.

Based on cylinder throats measurements, should I go 0.412" for sizing or can I stay with the 0.411 die I'm using.

Is my leading from boolits being undersized to the throats?

I want to get the 412640 mold in hand so I can get started with some serious testing. Thank you all. Brad

[kevmc]

Sounds like sizing....I'd go .412, but .411 may work.
Just don't see your current .4105 size as big enough..........

[cbrick]

I'll suggest a couple of things.

.4105" might be a tad small for a .410" groove diameter.
By 50/50 I assume you mean half pure and half WW.

With leading at the beginning of the rifling their could be some blow by with 50/50, boolit could also be a bit soft causing stripping as it takes the rifling. Could also be a combination of these two. At any rate those are the two main causes of leading in the first part of the rifling.

Rick

[BK7saum]

Sounds like sizing....I'd go .412, but .411 may work.
Just don't see your current .4105 size as big enough..........

That's what I was thinking, but is what I have to work with at the moment. In a few weeks, I should have the 412640 in hand and will not have to worry about undersize boolits.

I am sending work out to Buckshot and will probably add a 0.412 lubesizer die to the order.

Thanks, Brad

[BK7saum]

I'll suggest a couple of things.

.4105" might be a tad small for a .410" groove diameter.
By 50/50 I assume you mean half pure and half WW.

With leading at the beginning of the rifling their could be some blow by with 50/50, boolit could also be a bit soft causing stripping as it takes the rifling. Could also be a combination of these two. At any rate those are the two main causes of leading in the first part of the rifling.

Rick

Yes, 50/50 is half pure and half WW. That is the alloy I shoot in 45acp and 38 special. These loads are not any hotter than those, just a mild plinking load.

I have plenty of WW and might try straight WW, but won't be able to get around the undersize boolits until I get the new mold. I don't plan on keeping the lee mold. It was something I picked up here to see if it would work, but its not working well. I'd lap it larger and keep it if i liked the profile.

Rick, that information is exactly what I was looking for. Thank you.

I'm hoping to hear from Mihec any time. Got the paypal ready to go.

Brad