School me on gain twist. How does it work and what is the best use for it?

With gain twist, the twist rate is slowest in front of the chamber and increases to end up fastest at the muzzle.

Perhaps the most common example is with old Italian Mannlicher-Carcanos.

Best use is when shooting from school book depositories.

They worked well there huh?

Rock Creek barrels are gain twist and have been for a long time. I believe it reduces pressures a bit. They have always been very accurate for me.

Supposed to mitigate bullet poofs.

Gained traction with the soft plain base lead bullet target shooting crowd over a century ago. Harry M. Pope was a noted advocate of it. Eased said soft bullet gently into the dynamics of the rifling and ended up spinning it at the desired faster rate as it left the muzzle. A couple current niche barrel makers who cater to the single shot crowd still tout it but as far as I know the jury is still out whether it is beneficial or not. I will say some impressive results are to be had, but who knows if its because of gain twist or because of meticulous workmanship. Pros and cons are debated in ASSRA forums at least once a year.

My Pope-barreled 1885 High Wall Winchester .32-40 has gain twist rifling and shoots sweetly indeed, but who's to say if it's due to the gain twist or Pope's dedication to perfection. Ditto my .32-40 High Wall built by an unknown in the 1960's.** (Both LH twist too, by the way.)

**By the way, if anybody knows the identity of a smith from 50-60 years ago, in Indiana probably, whose initials are "TJF", I would love to know his identity. He built said .32-40 rifle.

I believe Bartlein barrels are gain twisted as well.

Early Colt percussion revolvers were said to have had gain twist barrels.

Oh, and speaking of beaver shots:


“Thank you. I just had it stuffed.”

I had one of Charles Askins rifles for a while. It was a Winchester 70 converted to left hand, chambered in 308 Norma Mag and had a gain twist barrel. As near as I could tell using a cleaning rod with a tight patch and making careful measurements, it started around 1/16 and finished around 1/9. It wasn't a particularly accurate rifle but I didn't do any real exhaustive load development. It shot a good consistent 1 3/4"-2" with 180 grain Partitions and I called it good enough with which to hunt moose.

You can order a gain twist barrel from bartlein. But you have to specify exactly what you want. There regular barrels are not gain twist.

This is a gain twist Bartlein 30 cal that was used for a 300 wsm. It starts out at 10.75 At the chamber and exits the barrel at a 10 twist.

Winchester model 63 had increased right hand twist and even with crappy ammo it hits harder than it should.

Accurate too.

So I am guessing that the bullet will to continue to increase rpm's as it continues down range . Does this make it more stable at longer ranges 5,6,8 hundred yards or more ? Or is this project made up for the benchrest crowd to argue about?

Think carefully about that for a minute.

In a word, no it won't.

OK that's what I couldn't exactly get my head around ,so if it starts at 1-10 and finishes at 1_9 it's it's going to continue at 1_9 throughout the rest of it's flight.

Not quite, but it's a little more subtle. When it finished at 1-9 it was mechanically coupled to the barrel and its rifling. Downrange is different.

As the bullet travels through the air its forward speed and rpm both decrease. Each 9 inches the bullet travels downrange takes longer than the previous 9 inches. The forward speed of the bullet decays faster than its rpm, so even though the spin is slowing the bullet gets more spin into each 9 inches of travel downrange.

OK got it thanks.

It's not talked about too much but more than a few long range benchrest shooters use gain twist barrels. Typically a very slight gain, say starting out at 8 3/4 twist and finishing at 8 twist.

Does it really stabilize the bullet enough to make it worthwhile?

Come on mathman - DO YOUR RESEARCH! 🤣

The faster you spin a bullet the tighter it spins increasing BC for really long range shooting. This is according to Brian Leitz and his team has won the 2 mile shoot multiple times.

I was quoting him. What are you talking about?

I'll expand on Tyrone's statement a bit since Service Rifle competition is one of the places you'll see gain twist barrels. We use fast twist barrels (up to 6.5 twist) to stabilize long skinny bullets (90gr) to improve wind performance. The fast twist coupled with pushing the 223 case HARD sometimes results in jackets coming apart downrange. A gain twist barrel supposedly starts off spinning the bullet more gently (9 twist) and accelerates the twist down the barrel until it's at 7 or 6.5")...I'm not sure if it works or not. I posed the question, if the rifling is essentially plowing a new furrow as the bullet goes down the barrel...how is that better for the jacket? I will say however that the folks that I know shooting a gain twist are getting crazy velocities. But is that a function of the gain twist or their lack of regard for pressures...again, I don't know.

"if the rifling is essentially plowing a new furrow as the bullet goes down the barrel...how is that better for the jacket?"

That's something I've wondered about.