The thread on polygonal rifling made me remember something. I heard that there was a company that had made soem variable twist barrels, say starting at 1 in 14" then towards the last few inches it would be 1 in 10". If I remember correctly the person telling me said that this wouldn't slow the bullet down as much and that the accuracy would be the same as what mattered was the rotational speed of the bullet at muzzle, and that the last few inches were sufficient to take care of that.

Anybody know anything about this concept and whether or not anybody is making them?
Red

I've heard of these barrels; I don't know who makes them. The principle sounds plausible, however, I am wondering if the changing pitch of the riflings as the bullet travels through the barrel would cause the bullet to exit the muzzle with a "rough" exterior, similar to a stripped thread on a bolt. Any thoughts from you long-timers in this sport?

Gain twist has been aroung a long time. I can think of three now making them: The Gain Twist Barrel Co. and Apex. A gent in Canada, think his name is Ron Smith, also makes them.

I have a 30 cal. gain twist barrel on the rack for future use: 60 inch twist at the breech, 10 inch twist at the muzzle. Think it will be a 300 Ultra.

Is gain twist any better? Don't know. But, Uncle Sam uses them on the 30 MM Warthog guns, maybe more calibers. Theory is gain twist is easier on heavy large caliber bullets, and on lead bullets.

The benchrest guys say a hummer barrel has a slight gain in twist from breech to muzzle, maybe 1/2 inch or so. And a so-so barrrel has a slight loss in twist from breech to muzzle. Before button rifle barrel makers started using positive twist guides for the buttons, this slight gain or loss could be caused by button pulling variations, like torque wind up in the pulling rod. Still can happen somewhat even with a positive guide. There was a bit of press on this subject several years ago in Precision Shooting.

fantastic information! I have 3 rifles with apex barrels, older though. I didn't know that the company was still around. Maybe it is a different company.

It's amazing the things that have been tried in the quest for better firearm performance.

Red

I have a Ron Smith gain twist barrel on a .30-BR AMT benchrest rifle.

Contrary to what I anticipated, it shoots jacketed bullets very well. However, it will not agg proven bullets and loads with cast bullets well. Instead of the sub 0.3" and 0.4" groups those cast bullets normally shoot from consistent twist barrels, from this gain twist barrel they shoot more like 0.6" & 0.7" aggregates.

It's possibly also worth noting that gain-twist barrels can't be lapped after rifling, except with VERY expensive equipment that still doesn't allow for the "feel" of hand lapping. I don't know of any independent custom barrel makers who could afford that equipment for the small number of gain-twist barrels ordered, anyway.

Thus, as noted BR rifle builder "Speedy" Gonzalez commented about my barrel..."The tops of the lands are nice and smooth, but the bottoms of the grooves are the roughest I have seen in a custom barrel."

AC

[ 06-07-2003, 03:31: Message edited by: Alberta Canuck ]

I have several 30-cal gain-twist barrels made by the same maker as John Ricks although mine are both 1-50 at the breech and 1-10 at the muzzle for a "gain" of 5 to 1. One is on a rifle and the other is "on-deck" for a future project if I can ever make up my mind.

The comment about difficulties in lapping them is true as the maker told me to use the Tubb's FinalFinish process to do the final lapping of the bore. Per his suggestion I used only the 4 finer grades of bullets and the bore has never fouled and feels slicker than owl s#*t when you run a patch down the barrel. A side benefit of using FinalFinish this way is it also "breaks in" the barrel at the same time.

I had thought about using a gain twist on future a 45-70. I thought it may be easier on the cast bullets.
Does anyone make a squeeze bore? Say going from .4595 to .4565 at the muzzle, again for cast bullets. Not sure what I'm achieving doing this but seems to me that the constriction would aid in keeping the gases behind the bullet. may make for a more complete burn of the powder also.
Jim

i just got a 257 barrel from Ron Smith. it starts off as a 14.5 twist and ends up at 9.5. i cant wait to shoot it. it looks good.

Hello All - mainly OT

DB Bill "feels slicker than owl s#*t"

I must write in defence of the African Giant Eagle Owl.

I raised one from a small ball of yellow fluff to all of his 48" + wingspan. He never once produced anything other than bone-fragment reinforced, dry waste pellets. The greatest problem in after-meal cleaning up was collecting the pinion and tail feathers that he carefully plucked from the pigeon before eating everything else.

Arkypete - squeeze bores

Must be a German thing - the 88mm of WW2 reputation had it as does my 8x68 hammer forged Sauer 80. Maybe all those 8s ... :-) Although in the hammer-forged case I suspect it has more to do with ease of recovery of the mandrel from the finished barrel than anything else.

Following on from a thread on another board, I'm busy sketching a barrel making whatsit to cut rifle gain twist and squeeze bore simultaneously - just seems like a good thing to try - just don't hold your breaths.

cheers edi

I have three Ron Smith gain twist barrels, a 284 Win, a 340 Wby and a 240 Gibbs. All are very accurate (the 340 so much so that it's scary). I still have doubts about the theories as to why, but I have no doubts about the fact that , in a Ron Smith barrel at least, they work. As to the squeeze bore (slightly smaller diameter at the muzzle then at the breech end of the barrel), if I remember correctly this was one of the reasons touted by Colt as to why their Pythons shot so well. - Dan

[ 06-08-2003, 06:27: Message edited by: dan belisle ]

I understand that the hyper-accuracy gunsmiths always mike both ends of a new barrel and chamber the larger end thus creating something of a squeeze barrel.
Gain twist has been around since before WW1 (I think). It sorta comes and goes. I also think if it was the do all be all, it would be the standard method of rifling now. I think its kinda like flutted barrels. It looks kewl and its different.

Gain twist has been around since well before the days of Axel Petersen, George Schoyen, Harry Pope, etc.

Pope's barrels were commonly cut with gain twist.

My Ron Smith barrel is very accurate too...just not with cast bullets. (It starts at 1 turn in 19.6" and increases to 1 turn in 10.1" at the muzzle.)

Bev Pinney of British Columbia won the U.S. Cast bullet BR Grand National Championship in 1998 with a Ron Smith gain twist barrel in .32 Miller Short, but his barrel was plenty rough on his cast bullets. It leaded so badly he had to clean every 5 rounds, even in the 10-shot group matches. Literally long slivers of lead much like christmas tree tinsel came out each time he cleaned it. If Bev hadn't been a very experienced and self-disciplined shot, it might have rattled his cage. As it was, he just accepted that as a trade off for it's excellent accuracy, cleaned when he needed to, and proceeded to win.

That's the same kind of shooting that also put him on several Canadian Palma, National Small Bore, and other national teams. I also suggest Bev might have won with a Joe Pfigelputzimheim barrel made in Joe's unheated silo just north of Prince Albert during the dark of the moon in early January. Bev's that calm & collected a shooter.

AC

[ 06-08-2003, 09:56: Message edited by: Alberta Canuck ]

The taper bore is something I have read about in two places. I have seen it called Gerlich and Gerlach bores I'm not sure which one is spelled correctly. The original was a German antitank gun and the projecitle had collapsable skirts that would fold down as the bore decreased. The two sources I found it in are the A-square realoding manual in reference to the .416 Gerlach and in the book "Weapons". I've read about the gain twist barrels, but I can't remember where, that the gain twist barrels are hard on bullets because they are being stressed at different rates along the bearing surface. I'm sure if this is true or bad maybe one of the engineers or others of that ilk could clarify this.

Ah guys, gain twist has been around about as long as rifling has. The 1858 Remington cap & ball pistols used gain twist barrels. It works best with soft pure lead round balls as the very short engraving distance of the round ball and the soft lead will seal better than the longer, harder modern jacketed bullet.

I have two Apex gain twists, both in 338. I got them about 4 or 5 years ago, and, yes, the company has changed somewhat from the old Apex. One barrel is a Jamison and the other a WSM. Both are quite accurate but I don't know that they are any different in that regard as a conventional.

The reason I used them was the general belief that they provide velocity equal to a barrel 3" or so longer. I was building light mountain rifles. In the Jamison cartridge I had the opportunity to shoot a 24" barrel chambered with the same reamer as my 21" gain twist. The velocities were equal on both with the same loads, which doesn't necessarily mean anything as differences in bore size could account for it. Both showed ejector marks at the same point in stepping up loads and in general they performed equally. Don't recall where mine started as regards twist, around 16:1 I think, but one exited at 10 and the other at 11.

Didn't the Carcano's have gain twist barrels also? Seems like the long 6.5s would have a time negotiating the increasing rifling pitch. Plateau Hunter