Progressive Rifling

Google gain twist.
I believe Smith uses a gain twist on the 460 S&W magnums.
Not sure about which ones, but I know it's been done in rifles.

Bartlein will make a barrel with any twist, any twist progression.
https://bartleinbarrels.com/t-style-rifling/

There is a guy in Canada who makes BPCR gain twist barrels.

Makes a lot of sense on BPCR shooting long soft bullets. I think the Carcano used gain twist because the bullets were very long for caliber and needed a fast twist rate. Maybe had problems with the bullets stripping the rifling initially, don't know the whole story.

i remember reading the Pietta shooters model (high end) had it... just checked, yup, still does.

Kp321 said:

Makes a lot of sense on BPCR shooting long soft bullets. I think the Carcano used gain twist because the bullets were very long for caliber and needed a fast twist rate. Maybe had problems with the bullets stripping the rifling initially, don't know the whole story.

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Supposedly the Italians used gain twist barrels as an economy and accuracy reason. They lasted longer and some say are more accurate as the bullets did not suffer as much deformation. Their military teams still used carcanos in shooting matches for some time after wwII.

Google carcano homepage which has a bunch of information about the rifle.
http://personal.stevens.edu/~gliberat/carcano/
Also see W.B. Smith's book on the Mannlicher of which Carcanos are a variant.

The long rifle Carcano's barrel twist goes from 1-19.25 inches at the breech to 1-8.25 at the bore w/ 163 grain, .267 bullet,. People who cut those gain twist barrels to make a sporter or carbine are what gave Carcanos the unfair reputation for inaccuracy. The bullet stability, gave it the reputation of a wounding round causing through wounds rather than yawing like the Brit Mark VII.

Harry Pope made progressive-rifled barrels for Savage for decades. Since it usually took him a week or more to make a barrel, I'm assuming it was some kind of "custom shop" option.

Stevens, not Savage, and three years, not decades.

Jim Watson said:

Stevens, not Savage, and three years, not decades.

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You made me look it up--interesting secrets maybe of Pope and his progressive twist rifling

http://www.shilohrifle.com/forums/viewtopic.php?t=7632

I found a reprint of Pope's 1899 catalog.
"The man who buys a Pope rifle improves his scores."

At one of the Safari Club International conventions I attended, I asked a S&W rep about the gain twist in their 460 S&W Magnum revolvers. He called an engineer who had worked on that gun. The twist started at 1:100 at the breech and went to 1:20 at the muzzle. The purpose was not to keep bullets from stripping but because the brisk torque produced was very hard on scopes.

I can attest to the 460 S&W Magnum being hard on scopes. I've had at least 2 or 3 scope malfunctions on my Encore in that chambering (which doesn't have a gain twist barrel) the last one being in a top-of-the line Leupold handgun scope.

Kent Lomont said of the .44 Automag. Use Leupold scopes. They will all kick loose, but Leupold lasts longer and they don't charge much to repair them.

I've had a couple of scopes repaired by Leupold and they charged me nothing.

I broke 2 Thompson/Center Recoil Proof handgun scopes and each time the broken scope was replaced with a new one with no fuss.

I broke one Bushnell "Recoil Proof" handgun scope and they refused to fix or replace it saying it had been "abused." The only abuse had been using it on a heavy recoiling handgun.

I have a few gain twist rifled barrels.

http://schuemann.com/Portals/0/Documentation/Webfile_AET_BARRELS.pdf

jmorris said:

I have a few gain twist rifled barrels.

http://schuemann.com/Portals/0/Documentation/Webfile_AET_BARRELS.pdf

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Interesting perspective from a manufacturer.

Original Colt black powder percussion revolvers had gain twist rifling.

Gaucho Gringo said:

Original Colt black powder percussion revolvers had gain twist rifling.

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I did not know that. Thanks.

"Progressive" rifling is usually interpreted to mean rifling that is deeper at the breech and getting progressively more shallow towards the muzzle. English rifles often had this feature beginning with the 1853 .577 Enfield. "Parker rifled" .22 rim fire rifles where made with bores that had deeper grooves at the breech and taller lands at the muzzle. Such a bore had a larger groove diameter near the chamber and a slightly smaller groove diameter near the muzzle or "choke bored."