Has anyone experience, or
can anyone show me informations about it?

And what's your opinion, as well, about it?
Would it really cause smaller resistance in the beginning phase, would this compensate the presure and would it be at all better for the heavier bullets, at least ?

Thanks.

Koce---

It's called "gain twist" and was pretty much beat to death 200 years ago.

It works well with low pressure cartridges (black powder), but the manufacturing process is not precise enough to give added accuracy with modern cartridges.

Several barrel makers have done it. I don't know of one on the market now, but it wouldn't surprise me.

I tried a 14 to 12 6mm 30 years ago with a bench gun, but accuracy wasn't up to par.

I've used gain twist in two barrels, both in a 338 wildcat. The barrels are both 21". Their reputation is that the gain twist "adds" about 3" of barrel, hence my configuration. Velocity figures I achieved compared reasonably with those published by the developer of the wildcat with a longer barrel, however he used an Oehler M43 to check pressures and I didn't. For this reason I don't know if the velocity I achieved was over his pressures or not. In a direct comparision with another standard 1:10 twist, but a 24" barrel, there was not difference in velocity before external pressure signs showed up. I concluded the claim it added 3" to the barrel was valid.

The biggest problem is finding good barrel makers that can provide them. Mine came from Apex Barrels in Flagstaff, Arizona. I was only able to find one other maker, in Canada, who could provide one. If you want a light, handy, short rifle I'd say it makes sense. I'd do it again but I wouldn't say it's any great advantage and may be more trouble than it's worth.

Gain twist barrels are a bit uncommon and are perhaps a bit of a novelty. The primary reason I have used them is to have something different. Accuracy seems to be no better but no worse than with a uniform twist barrel. Also I have seen no definite evidence of any ballistic advantage.
A disadvantage, from the manufacturing standpoint, is that lapping is not possible due to the changing pitch of the rifleing.
I recently fired a 6BR with a gain twist barrel at 700,800,and 900 meters. The barrel was 27 inches long. Velocity was 2950 with 105s and the rifle seemed to be shooting about 3/8 MOA if the effects of the wind were discounted. I doubt that any uniform twist barrel would have done any better. The velocity,while impressive, is not out of line with what is being achieved with uniform twist barrels. This barrel is by Ron Smith of Wimborne, Alberta whose barrels are equal to any. He cuts barrels in both uniform and gain twist.
I like to stay with a fairly moderate gain ie. 12 to 8 as I feel accuracy is better. This is my opinion only. I will be assembling a Hunter class BR rifle a little later with a gain twist and we'll see how it does. Regards, Bill

What happens to the rear of the bullet as the front gains in twist? Seems to me that as the front engages in a higher twist the rear must either skate across the rifling or the jacket twist - maybe on a fractional amount but surely some?

The gain is gradual over the entire length of the barrel as I understand them, so the gain is constant, therefore the pitch remains the same. There is not a 1:12, then a 1:10, then a 1:8 section.

1894, you put your finger on it. The result of the shear means the jacket and core are going to have problems, unless you have a very thick jacket.

I've always wanted a gain twist, and shoot Gerards or other driving band bullets. There, the deformation would not matter.

One of those "just 'cause" things. FWIW, Dutch.

Thanks, Bill, for the name of Ron Smith. I spoke to him. He's very knowledgeable and obviously a craftsman.

What happens to the base of the bullet? The gain is so very little that the difference in any angle over the bearing surface of the bullet is unnoticeable. I've taken game with mine and bullets perform identically to a uniform twist from examination post mortem. I don't recall the numbers on mine, but on one, the departure of the bullet from the barrel is equal to a 1:11 twist. It starts at just under 1:14.

Mic McPherson has written about gain-twist barrels in both Precision Shooting and Petersen's Rifle Shooter (?) magazines. The article in Precision Shooitng is very good but doesn't come to any conclusions it just discusses some of the problem areas.

With a moderate gain any deformation is insignificant. The advantage to the changing pitch is better sealing. This may be why they are so good with cast bullets. I avoid a radical degree of gain out of a concern about deformation founded or not. Regards, Bill.

Its not only that the front and rear of bullet follow separate twists, also the angle of the rifling changes:

In regular twist, the rifling is engraved into the bullet at the throat. In gain twist this constantly changes, so the marks on the bullet are changed by passing through the rifling!

Those two arguments and the difficulty in manufacturing an accurate barrel should be enough to explain why the gain twist went out of fashion.

Hermann

I don't know about fashion, but I have two rifles with Ron Smith gain twist barrels, and the two of them are remarkably accurate. The 340 Wby seems no quicker than a regular twist rifle, but punches cloverleaf groups with 250 gr bullets as long as I can stand the recoil. Same with the 6mm. Maybe it's just because it's a very well made barrel, but these two sure work well. FWIW - Dan

aHunter,
The changing of the grooves on the bullet is something that happens more in the mind than in fact. That is if the gain is reasonable. I suspect the main reason the gain twist went out of fashion is that it is difficult to make well and quite honestly the uniform twist works at least as well and always has.
Harry Pope was a great advocate of the gain twist and there is little doubt that his were fine barrels but the unform twist barrels of George Schoyen, Horace Warner, or William Billinghurst shot just as well so that even in the old days the easier way may have been the better way. Nonetheless I do like the gain twist barrels by Smith and use them often. Regards, Bill.

Thanks a lot guys!

I only wanted to know a few some other opinions,
it started as a friend of mine said that he would try something very different, but very difficult to do, and who knows ...
He ment a dain twist that begins as 1:endless (in fact parallel to the barrel axis) and ends as 1: 10, 9 or even 8! and should have an effect as the "TRIBORE" system in any smooth barrel.
I thought it were mad idea, but mad people make mad success sometimes.
I also thought that such a gain wouldn't be easy to pass through without side effect, but the "heavier" bullets are usually solid, or with solid jacket - so it would be acceptable to expect only brighter trail...
OR ?...


koce ?

koce.......I have a gain- twist barrel (.30 caliber) that begins a 50:1 and ends at 10:1 with a barrel length of 24".....I haven't shot it a lot (yet) but I've learned several things already (1) I have seen a real increase in velocity over what I've seen in similar rifles in the same caliber and the same brand barrel with a standard twist (2) it handles both the 165gr and 180gr Nolser Partitions with equa (very good)l accuracy (3) I haven't shot it much past 100 yards but my 200 yard efforts show more accuracy than I would have expected...only about 40% larger than my 100 yards efforts, (4) doesn't appear to be finicky abou tthe powder used. The only down side I've seen is it is a little harder to clean than a standard barrel as the patches seem to want to skip along the bore if not careful. Oh...the barrel is button-rifled and stainless in a fairly light countour.

I would provide more specific information but I want to get a couple of hundred rounds down the barrel and I just haven't had the time...hopefully this will not be the case much longer.

DB Bill-----

Who's barrel is that? I've always thought a button couldn't be made for gain twist because the lead angle of the button *determines* the twist.

I can't figure out the process by which the button could be made to rifle a barrel if not by the lead angle.

There doesn't seem to be enough torsional force available on a rod small enough to fit through the bore to create, much less change, the twist.

I'd like to talk to the maker and find out how he solved it.

I have use a couple of Montana Rifleman gain twist and I wasn't at all impressed...It never has worked with any consistency....It was hype back when and still is today I suspect. Some of them probably did work, but most didn't but thats the way it is with barrels, they are a crap shoot, unless your shooting Lothar Walther of course

Gain twist are cut rifle barrels I'm sure, or pretty sure at least.

I knew I should have stayed out of this. The maker isn't prepared to go into production. I got two .30 caliber barrels to try thru a friend in the firearms industry who didn't have the time or interest in working on them himself. One has been made into the rifle I mentioned and I still have the other...both are 24". I wish the unfitted one was 26" or 28" as I believe cartidges that are thought to be "over-bore" might get the most benefit from this extreme a gain-twist.

This project of mine has been languishing for to long and I will get to it soon and trust me guys the barrels are button rifled.

I will stirr the pot! Got a 30 cal gain twist barrel on the bench, 26 inches long, in No. 7 HV taper. Starts at 50 inches at the breech and ends up 10 inches at the muzzle. Now,, get this, it is chambered in 30 Steyr. (Bet you have not seen this cartridge!! It's the 376 necked down). This barrel was on a Sako action, has shot sub 1/2" groups. Its one of the barrels McPherson wrote about. I pulled the barrel a month ago in order to install a prototype carbon fiber barrel.

I am thinking about rechambering the gain twist to 30 WSM and putting it on a M70.

And, to kick the pot, this gain twist barrel was made on a computer controlled button rifling machine, the same one that made DB Bill's barrel. There is a long and complicated story as to why this machine is not being used, I cannot go into the details. And the buttons are a well kept secret, they do not look like conventional rifling buttons.

And, yes, there is a way to hand lap a gain twist barrel, I will have to post some photos of the equipment I made to do this.

And Uncle's using 20mm and 30mm gain twist barrels, ask Steve Webb (Apex) about them. I was talking to Cliff LaBounty today on the phone, interesting, one of the subjects was gain twist.

Lothar Walther has produced gain twist barrels in the past using button rifling. This was discontinued over 15 years ago as a production item as there was no definite difference in accuracy when compared to an absolutely identical non-gain twist barrel. (for use with jacketed bullets) For use with lead bullets, there is an advantage.

However, about ten years ago, we started producing a much newer version which we call progressive twist. When matched with the cartridge and the use of the weapon, the barrel will give increased accuracy within a very tight design parameter. However, there is very little flexability in loading and use. It is common for rimfire. Rimfire barrels became available with this feature in 1995 for OEM use and in 2000 for individual use.

The process is radically different for centerfire. The amount and timing of the "gain" section is critical and without CNC rifling equipment, it is impossible. Cut rifling, with a clockwork mechanism can easily make gain twist, but buttoning, with special geometry buttons can open a whole new area of technology.

The largest problem for the individual barrel purchaser or shooter is that the barrel has to be made to be used at a set length, so a generic barrel blank, to be turned to a variety of contours and lenghts will not be possible. It will be seen with the greatest benefit in production guns.

Several production runs of AR type barrels with this feature have been made and the accuracy is excellent.

Woody, is there anywhere we can find out more about this feature? It almost sounds like you are designing the barrel / load combo to minimize the vibration? Dutch.