Another .357 conversion.

[Texas by God]

Great looking stub job. I blind pinned my 44-40 under the frame line as well as using JB Weld on my Topper. I want to do another- I have an old Stevens 94 16 gauge that needs to be made into something that spins boolits!

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[Texas by God]

Leaf springs can be lightened by grinding their legs into an hourglass shape, using water for cooling. I wouldn't do it without a spare handy.

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[sukivel]

Ok I want to do this. Couple questions...

I have a new 20 gauge barrel lying around...is it too small or do I need 12 gauge. And regarding the pressure issue, how do you determine the breech itself can handle the difference in pressure?

The OP gun ended up nice. What gauge did this start as?


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[Michael J. Spangler]

All good questions

Are any donor guns ok to use as long as they are sounds and fit to fire 12 gauge from the start?

[tbx-4]

sukivel,
I’ll do my best to answer your questions.

1. To make the .357 barrel fit inside the 12 ga barrel I had to turn down the .357 barrel on a lathe to fit the chamber and bore. This applies for your 20 gage barrel as well. So do you have a lathe? If yes then it’s up to you if you want to try this.

2. This old shot gun was designed to fire 2.75” smokeless 12ga cartridges which will produce about 5000 psi bolt thrust. .357 magnums produce just under 4000 psi bolt thrust.
Bolt thrust is max pressure x inside case head area.

MJ Spangler,
If it were me and the shotgun is sound and made for smokeless I wouldn’t hesitate but I cannot give advice on anything you might have or do with it. I think for myself that 12ga is a good staring point.

[lar45]

You need to calculate the bolt thrust to see if the action will handle it.
The area of the shotgun shell is pi(3.14)x the radius squared. then multiply by the chamber pressure to get force exerted onto the breach.
Then take the size of the new cartridge(357mag or whatever) and do the same calculations.
If the bolt thrust of the 357 is smaller than that of the shotgun shell, then it should be safe to do.

If you want to convert to a higher pressure round, then you might have to look at the fireing pin and hole. Some old shotguns have a large firing pin hole that the new high pressure primer might want to flow back into. You wouldn't want to have a primer get pierced, or fail and get gas back in your face.

I used to have a great book on converting double barreled shotguns into double rifles. I think it was by W. Ellis Brown. The book used to be fairly affordable, but has become quite expensive the past few years.
https://www.amazon.com/W.-Ellis-Brown/e/B001K90B9A

[lar45]

Here is a quicky Excell sheet with a few different rounds thrown in.
http://www.lsstuff.com/misc/bolt-thrust.xls

[Texas by God]

The firing pin and hole size are important as mentioned. I would not use any cartridge with higher pressure than 30-30 Win for this. Pistol/ revolver cartridges and BP orgin rifle rounds are good choices.

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[sukivel]

Here is a quicky Excell sheet with a few different rounds thrown in.
http://www.lsstuff.com/misc/bolt-thrust.xls

All I would want to do are pistol rounds...this spreadsheet work great, thanks!


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[sukivel]

I got to thinking...

My 20 gauge barrel is a new barrel from a new gun that is made to buy and swap barrels. Going off the previous chart, would it not be reasonable to use the info for the highest pressure barrel made for this gun/barrel combo? And not exceed that pressure? I know they make a 308 barrel for this gun.


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[tbx-4]

Your shotgun barrel is just acting as a sleeve. It doesn’t contain the pressure, that’s the job of the inserted barrel.

The next critical item is the shotgun frame can it withstand the bolt thrust, this includes the locking mechanism and hinge.

[tbx-4]

So doing a little math here.
20ga max pressure is 12000 psi times area of inside head case .331 sqin = 3979 psi bolt thrust....
This is almost exactly the same as .357 mag bolt thrust. I’d feel safe if it was me especially using a new barrel and action.

[sukivel]

So doing a little math here.
20ga max pressure is 12000 psi times area of inside head case .331 sqin = 3979 psi bolt thrust....
This is almost exactly the same as .357 mag bolt thrust. I’d feel safe if it was me especially using a new barrel and action.

Yeah agree there, but since they offer a barrel in .308 for the same action, couldn’t I use it for say, .44 mag?, even though the thrust on that is more. I guess what I’m saying is shouldn’t we use this equation on pertaining to the action, and what it’s rated for, instead of the barrel, which is only a sleeve?


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[Texas by God]

Think of the original Contenders. Experimenters like Herret and Jones discovered that the standing breech would take low pressure rifle rounds that the factory didn't offer. It would also stand a high pressure round like the .223 because the area of thrust is smaller. On older cast steel single shots shotguns I would err on the mild side.

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[Steppenwolf]

Excellent result. A fine way to bring and old shotgun back to life.

[Texas by God]

Sukivel- do you have a Rossi or a H&R/NEF? Either would work fine for the .44 Mag.

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[tbx-4]

Sukivel- do you have a Rossi or a H&R/NEF? Either would work fine for the .44 Mag.

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Yes, knowing what action he has would help. If it’s an H&R SB1 then pistol only. SB2 is good for rifle cartridges. Don’t know about Rossi.

[sukivel]

Yes, knowing what action he has would help. If it’s an H&R SB1 then pistol only. SB2 is good for rifle cartridges. Don’t know about Rossi.

Haha, curveball...it’s a Rossi Wizard. I never heard of one til I traded for it. Several years ago I bought my son the Rossi Trifecta, which came with .243/.22/20 ga barrels. Very low quality and had lots of problems. This wizard is a whole lot better with wood stock. They weren’t sold as combos but you could buy separate barrels for them. I traded for a 45-70 and a new unused 20 ga barrel. It shoots pretty good and works good 90% of the time. Sometimes it’s difficult to break open, but slapping it underneath opens it up. Only put about 50 rounds through it so far.


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[sukivel]

In my neck of the woods these single shot shotguns are everywhere for sale. I love these breakover rifles and would like to have several of the rimmed pistol calibers. I love H&R’s but they are sometimes hard to find and pricey.


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[Texas by God]

A used Topper shotgun is $70-$100 around here. I'd stub that Wizard to .44 or .357 Magnum as soon as I could get the desired barrel. Handi rifles aren't cheap anymore like you said.