poor performance with cast bullets

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3sharps
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poor performance with cast bullets

Post by 3sharps »

I have 2 Rossi and 1 Henry rifles in .357 magnum. I get good accuracy in all of them with jacketed bullets. When I load cast bullets my groups open up to 8 -12 inches at 100 yards. I slugged one of the Rossi barrels and it measure .355. My cast bullets are .356 to.357. Bullet weight is 150 grain. I have tried lubeing them and powder coating them. My best jacketed loads are with 15 grains of 4227 powder. I have tried 30/1 alloy and wheel weights. Nothing seems to help. Can anyone point out my error?
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Re: poor performance with cast bullets

Post by Ranch Dog »

How about a bit more info about the bullet; is it gas checked or plain base? Also, what about the nose profile?

Also, how are the two alloys withstanding the trip down the barrel? You sure the barrel isn't leaded up?

I have the same groove diameter, had two rifles both the same, and size the bullets at .357". I'm using a 175-grain and 190-grain bullet with a nose profile that matches the throat very well. The bullets are gas checked, cast with 95/5 wheel weights/tin, and they shoot exceptionally well. I push them hard to get past the twist rate of Rossi barrel (30).
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Re: poor performance with cast bullets

Post by Ohio3Wheels »

My 357 20" runs the same on groove diameter and shoots my home cast Lyman SWC gas check 158 +/- okay when pushed a little bit. Moving up to 180 grain commercial cast (Penn and Shamrock) and pushing with a stiff load of H110 with factory sights and these old eyes it will hold 3.5 to 4.5 at a hundred. Since it will stay under 2 at 50 I'm thinking it's mostly the eyes. We'll see when I get a tang sight on it. My available out door 100 yard ranges are closed for the season and/or remodeling so it's going to be March before I'll be able to do any more testing.

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Re: poor performance with cast bullets

Post by GasGuzzler »

There's at least five powders I'd use in .357 before 4227. Not saying that's the issue but...
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Re: poor performance with cast bullets

Post by Ranch Dog »

GasGuzzler wrote:There's at least five powders I'd use in .357 before 4227. Not saying that's the issue but...
My thoughts as well, but I'm not sure what he is trying to do with the bullet's velocity. It will never generate the RPM I think is needed. I want to see about 40K rpm from the 30 twist (1700 FPS).
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Re: poor performance with cast bullets

Post by GasGuzzler »

In no particular order...

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Re: poor performance with cast bullets

Post by 3sharps »

Okay, I have about 4 pounds of 4227 to use up. I can get good groups with 158 grain Hornady bullets. When I switch to cast bullets my groups more than double. From what you are telling me I need to get up to near maximum loads. I do have some tight group powder.
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Re: poor performance with cast bullets

Post by OldGringo »

My comment is that I can only be one of three things. First, the length of the bullet must be at a certain speed to work with the 1/30 twist. Probably your load is too slow. It would be interesting to see how it compares in length to your jacketed bullets and then try to match the speed.

Second, if all three rifles are doubling group size with cast only and the 158 grain jacketed bullets work fine with that barrel twist, it could be that particular mold. You might look closely at the bullets to make sure the sprue on the base of the bullet is not off center. That has been reported in cast bullet association info for a long time as something that creates big groups.

Third, the bullet is is too hard to bump or obturate to fill into the grooves, then you are getting some blow by, which of course melts the base a little bit. If you increase the velocity to insure a bump, then of course you might need gas checks to prevent leading. Although, your powder coating should resolve that.

There are lots of older blogs suggesting that the Rossis need a magnum level velocity for best accuracy. I have 2 Rossis and 2 Marlins. You can always load them down in 38 special cases and just shoot them at shorter ranges at smaller targets, lol, these plinkers work great in all 4 of mine. FWIW
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Re: poor performance with cast bullets

Post by Ranch Dog »

Yeah, I would look for another powder as 4227 is not going to produce an appropriate velocity. I have a bit less than 4 lbs of it and have never figured out what to do with it. I'm down to using it with a CC 38 Spl revolver, a Rossi 351, and I'm not happy with it even in that role.

Another question, is the 158-grain bullet an SWC? Though fine for revolvers in the same cartridge, I've found them lacking in accuracy from the rifles.
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Re: poor performance with cast bullets

Post by Iplayfarmer »

3sharps wrote:Okay, I have about 4 pounds of 4227 to use up. I can get good groups with 158 grain Hornady bullets. When I switch to cast bullets my groups more than double. From what you are telling me I need to get up to near maximum loads. I do have some tight group powder.
Have you tried a series of powder charges with the cast lead to see if there's a different sweet spot for cast lead than with FMJ type bullets? Lead and copper travel down the barrel differently, and it makes sense that the ideal powder charge would be different for each type of bullet. I don't know much about 4227, but I've had good luck with HP-38, HS-6, H110, and TrailBoss.

Like others, most of my preferred loads are toward the higher end of powder charge for each combination of bullet/powder.
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