1:16 twist okay for 357 carbines?

The Rossi Model R92, a lightweight carbine for Cowboy Action, hunting, or plinking! Includes Rossi manufactured Interarms, Navy Arms, and Puma trade names.
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1:16 twist okay for 357 carbines?

Post by trekker »

Rebarrelling an older 1892 Rossi carbine in 357, was thinking to go tighter than the usual 1:30 twist barrel. Barrel maker does a 1:16, was wondering if this is an appropriate twist rate for a carbine?

I was thinking would be nice to run heavy bullets with it, but was worried the faster speeds of a carbine with a tight twist might overstabilise 125 grain bullets?

Had heard rumors Rossi chose the 1:30 twist for this reason, highest velocities with lighter bullets...Then again Marlin apparently does their new 357 carbines in 1:16: so it must be okay?
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Re: 1:16 twist okay for 357 carbines?

Post by Ranch Dog »

The SAAMI Spec is 18.75, for bullets from 110 through 180-grains. This is based on pistols, there has never been a rifle spec.
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Re: 1:16 twist okay for 357 carbines?

Post by GasGuzzler »

1:16 makes more sense than 1:30 at least to me.
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Re: 1:16 twist okay for 357 carbines?

Post by HarryAlonzo »

Before you dive into rebarreling, you might want to read about the difficulty this guy had:

https://forums.outdoorsdirectory.com/fo ... ter-magnum
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Re: 1:16 twist okay for 357 carbines?

Post by trekker »

Could only open the first page of that thread for some reason. But the gun will be getting done by a custiom smith who does 50 Alaskans etc so I assume he can manage same profile round barrel in 357
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Re: 1:16 twist okay for 357 carbines?

Post by Archer »

I recall reading through this some time ago.
page 1 mentions die problems but that's not likely with .357 Mag and easy to find replacements.

Page 2 Funny thing, the threads mike at .748” so ¾” but the pitch seems to be 1.0mm . . . ya ain’t gonna find a nut for that at Lowes. I’m guessing because it’s a Winchester copy they made it ¾” but didn’t bother changing the tooling to cut inch threads on it or just don’t even have any settings to cut inch threads down there. Anyhoo, it’s an interesting odd thing I wasn’t expecting but no beg deal, I can cut 1mm pitch too.

Page 3 Barrel is done but for threads and chamber, spent most of tonight trying to get workable test threads to come out with no luck. These very fine 1.0mm pitch threads suck to cut in ¾” diameter boys!

I can’t cut them with my carbide insert threading tools. I can’t turn it fast enough for them to cut nice and be able to stop at the shoulder without CNC. They ether gall bad or just rip the tiny thread right off rather than cutting a grove. So I went to old school hand grinding HSS (high speed tool steel) bits, they cut fine but it’s hard to keep a fine enough tip for these extremely fine threads here. I just ordered a bunch of HSS threading inserts but I think I can get it to work with what I got . . . tomorrow maybe, when I’m not on the verge of chewing the threads on there with my good tooth!

They will cut cleaner in the 4140 steel of the barrel than my mild steel test rod but I ain’t trying until I’ve got some good test threads and know for sure that my set-up will work.


06-10-2012, 10:08
Well I considered that, also thought about getting a standard size die and opening it up. M19X1.0 is a standers size and real close at .744” (I need ¾” .749“ major diameter) so I went shopping, cheapest I found was $109 . . . I’m not cutting up a $109 die. There is a relief on the Rossi barrel and it makes things a lot easier so I’m cutting one just like Rossi did.

I will be able to single point it, I just got to figure out the best method to do it. After sleeping on it overnight I’m thinking I will cut them from the shoulder outward with carbide. Turn the tool up-side down, put the lathe in reverse and mash the gas cutting away from the shoulder so I have no danger of crashing into it.

06-11-2012, 10:29
Well I give up on single point cutting these threads, I got a (one) test thread to come out, with these extremely fine shallow threads it’s just too hard to be consistent. They aren’t deep enough or far enough apart for the tool to start tracking in the grove so any tiny hiccup grabs the tool and yanks the lash over ever so slightly . . . then I get pealing threads, galling, and/or snapping the tip off my tool. Very frustrating to say the least!

So I went die shopping, took about 3 hours but I found a M19X1.0 adjustable die from Japan for $30, I guess Honda taps some coolant port in this odd thread. I think the 19mm is close enough (.744” major diameter) I can open the adjustable die far enough oversize to get the .749” diameter thread I need


06-11-2012, 15:04
Originally posted by Amigo Will View Post
How hard would it be to scrap the receiver threads and match receiver and barrel as a take down?
Will ya think like me, but your gettin ahead of the curve a bit . . . I wasn‘t gonna talk about this till I was to that part of the build. Yea it would be real easy to make it take down but the receiver band is only about .150” thick under the threads so there ain’t enough beef to cut a lug type set-up in it for a ¼ turn tpe take-down. However I do plan to make it take-down while I’m building it here but a screw apart type so I still need good threads on my new barrel.

I will turn a second flat and shoulder on the barrel just ahead of the normal shoulder onto which I can tightly secure a lug something like a Remington’s recoil lug. After threading the barrel assembly on the receiver the magazine tube will pass through this take-down lug and into the receiver indexing and locking the two halves together. The magazine tube will then be held into the locked position by a spring loaded button at the muzzle band.

To brake it down you would depress the button at the muzzle, slip the mag tube forward a bit, and un-thread the barrel and entire front half of the gun off the receiver as one unit. My Uncle had a 94 30-30 like this and it's slick, not as slick as the 1/4 turn type but still very slick.


06-14-2012, 22:46
Nope, I got a double spider type fixture to chuck the barrel in. A pipe with 4 apposing brass tipped adjusting bolts at each end of it that chucks in the lathe allowing for fine tuning in all directions. There is no slop in the fixture or the chuck at all but there is about .01” (or almost 1/4 turn of the chuck at 1mm pitch setting) gear lash between the chuck drive and cartage drive half nut. I can cut good threads that would work for most things in one maybe two passes because it’s taking enough cut to track right, but, I can’t fine tune to proper tight size fit because the pitch is so fine.

1mm pitch is only .0394” thread peak to thread peak or 25.4 threads per inch, that’s extremely fine on ¾” diameter, standard ¾“ fine thread is 16tpi. In metric 19mm diameter is oddball (ISO standers is 18mm then 20mm) but if you can find 19mm fine thread is 1.5mm pitch. M19X1 is made but it’s a very odd duck.

With the ¾” diameter I’m getting ether one edge of the tool cutting and the other pushing on the unsupported thread and bending over or galling all up. Or it just peals the thread right off the stock because the thing is just as thin as a heavy edge burr.
I’m sure the adjustable die will work though. It can’t help but track as it supports the tiny little threads the way they are made and it will be faster than single pointing on the lathe too. It should be here Monday I think. I been stuck in the hospital all week with my Mom trying to die on me so haven’t had time to work on anything anyway.

Page 6 Barrel is done but crown, extractor notch and site notches. I was able to single point it all once I got a real good sharp HSS insert threading tool so I could go slow enough.

MORE Die problems, again specialty issues.

Problems with feeding, requiring adjustment of the guides. Problems with lifter requiring detent modification.

Also along the way he had issues with chamber gauge and reamer from the sound of it.

Guy seems more than competent machinist and pretty knowledgeable smith. Did all the work himself and caught a few problems with commercially manufactured parts along the way.
Project went on for about 9 months.
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Re: 1:16 twist okay for 357 carbines?

Post by trekker »

He might be a competent machinist but competent gunsmiths rebarrel leverguns with poor bores on the regular. No offence to the guy but he makes a lot about rebarreling the gun, whilst saying making it a takedown would be simple. :shock: To my thinking for lever actions those comments should be the other way around.
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Re: 1:16 twist okay for 357 carbines?

Post by Archer »

trekker wrote:He might be a competent machinist but competent gunsmiths rebarrel leverguns with poor bores on the regular. No offence to the guy but he makes a lot about rebarreling the gun, whilst saying making it a takedown would be simple. :shock: To my thinking for lever actions those comments should be the other way around.
I don't think he was a gunsmith by trade. Even IF he were he might well run into many of the same issues unless he worked on the same job before.

He was not just rebarreling it.
He was doing a caliber conversion to a 25 caliber based off the .357 that required the rebarreling and was doing the take down conversion while he was at it.

The problems were mostly regarding the fact that the thread pattern used by Rossi was more or less a hybrid for which tooling is not readily available.

Making a takedown IS technically pretty easy. NRA had an article on making a Winchester 94 into a takedown that I read several years ago. It involved dressing down the front of the receiver with a mill or file, modifying the mag tube to retain the follower when removed from the receiver addition of a plate about 1/2" thick milled to the section of the receiver behind the barrel and turning down the barrel forward of the aft threads for the plate to seat and a small modification to the mag tube and forward band to allow the mag to be withdrawn or seated in the receiver. There used to be a series of pictures on the web where someone did the exact same operation using a Rossi 92. I've always wanted to do one or more but 'cheap' lever guns rarely are inexpensive any more.

A whole lot easier than trying to machine an oddball thread pattern which IS what he ended up doing.

With the right tools MANY things get easier. Having done it once or twice and having the right tools can make it REALLY easy. What he ended up doing is getting better tools that enabled him to cut the correct threads. IF he'd been able to get the right die it would probably have been NBD. Paying for a specialty die may make sense if you are going to use it multiple times. Paying for an expensive tool for a one of gets expensive fast. If a competent gunsmith doesn't have the tool then the cost of the job may include it or at least as big a chunk as he thinks he needs to charge in order to pay for the tool over the course of the jobs he expects to use it to complete. Otherwise he goes out of business.
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Re: 1:16 twist okay for 357 carbines?

Post by GasGuzzler »

Archer wrote:Having done it once or twice and having the right tools can make it REALLY easy.
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Re: 1:16 twist okay for 357 carbines?

Post by trekker »

Well, whatever he was doing aside, a rebarrel by a guy setup up to do it is less technical than a takedown conversion. Thats all I need done. Interesting read though fellas, thanks.
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