I am just wondering what advantages there are with a gain twist barrel? I remember people talking about them mabye 6 yrs ago but havent heard much since until seeing references here. If I were to build a 358 win or a 284win is there any advantage to a gain twist? Thanks guys.

Got 2 26 inch S/S RKS barrels chambered for 300 Win and 7 mm STW.Both barrel exceed a standard tube easly by 200 fps.Actually my 300 is right on par with a Roy.

To me it's like up-gunning without going to a larger round.Alot of guys with gain twist chambered rifles use odd lenghts because the barrel makes up the speed.

My barrels shoot extremely well.One thing I have noticed is they can be picky to load for but when you find the right load they are straight shooters.Always get a kick when I show up at the range and blow peoples minds with the speed.First thing they all ask is to see the case.Once they see no pressure they really start to asks questions.From what I have seen I will never go back to a standard twists again.If you were to go 284 Win you'd be close to a 7 Rem.

Next chore is to crony that STW again in the spring.Did it before but can't rember the final numbers.But it's alot quicker than my friends Sako 75 STW.I do mean alot faster too.

Would you be more specific?Who manufacturers gain twist barrels?I have never seen them offered from the "main" makers.What velocities are you achieving from your .300 Win.?What barrel length?Bullet weight,etc.?I might be interested in a gain twist.Pros and cons?
Thanks,
Jim <img src="/ubbthreads/images/graemlins/help.gif" alt="" />

Gain twist barrels have no purpose IMHO. If they added velocity, long range target shooters would use them. They don't. If they added accuracy, they would also be common on the target ranges. They aren't. If they could add 200 fps as one poster claimed, then Roy Weatherby would have used them starting in the 1940s. He didn't.

The theory, I suspect, is to start accelerating the bullet gently, or not deform its shape. Fine in the 1800s but now we have jacketed bullets and, since they start from 0 fps anyway, that's gentle enough for them.

Variable twist must, by definition, change the angle of the rifling relative to the bullet. You end up at the muzzle with grooves in the bullet wider than the lands of the rifling, a deformation which defeats the whole purpose. Actually, I suspect this leads to more powder gas blowing by the bullet, which reduces velocities.

It was a throwback to early smokeless/late black-powder idea's in controlling fouling!
It was a idea more used on the other side of the pond than here.
Never proven to add in velocity nor help in accuracy department either.
Nothing more than a "gimmic" now days.
Mike

Agree completely. I have one in 338 Jamison, which is the same capacity as the WSM cartridges, and I had several 338 WSM's with standard twist barrels. Mine was made by Apex in Flagstaff, AZ (don't know if they're still alive!!) and I saw very little difference in velocities achieved between the Jamison and the WSM's with the same barrel lengths. It's no more accurate either. I ordered it for all the hype and have reached EXACTLY the same conclusion for almost the same reasons you give. Good post!

I own four gain twist barrels by RKS ( Ron Smith , here in Alberta).
There are only two or three gain twist bvarrel smiths in North America from what I understand.

The gain seems to help when useing ULD bullets at high veloctiy, but it will not "add" velocity, that is a charicteristic of a particular barrel.
It does sem to help in keeping fouling down, but that too may be because of the super finish that Ron puts into his barrles.

I like them, but also have a stright 8" twist RKS , and it is no less accurate!

Cat

IIRC, the gain twist idea in sporting arms was introduced to reduce felt recoil on heavy rifles. This was typically used in the large double rifles of 10, 8 and 4 bore, that routinely kicked the stuffing out of people. Rifling has a very significant role in the recoil department. The idea is to gradually introduce spin rather than all at once, and the concept does work. This concept was taken to it�s final evolutionary step when Fosbery patented the concept of the Paradox gun. The Paradox was a smooth bore shotgun all the way until you got to the last 2 �� of barrel, then he introduced a shallow rifling. With this, you can shoot a 750 grain bullet at over 1300fps and still have your wits about you after firing. To my way of thinking, the Paradox gun concept is just pure genius.

The heavier the bullet, the better it works. In something like a .30-06 or smaller, I doubt the shooter would ever notice a difference. S&W has opted to use the gain twist concept in their .460 XVR revolver, and with how well that gun shoots, who could argue with their success?

In the accuracy department, there have been any number of variations on the basic rifling concept. Metford, Whitworth, Ballard, polygonal etc. Generally speaking (not including the ridiculous). If the barrel seals the gas and imparts adequate spin, then they all work about the same (for sporting use, benchrest is another story). The deciding factor is usually the overall quality of the barrel, and that�s what makes a difference. If you have a gain twist of outstanding quality, it will always outshoot a mediocre conventional barrel. In the velocity department, I doubt there would be much of a difference.

For small bore (less than .45 caliber) rifles, most of the advantages of a gain twist are more theoretical in nature than actual.

Hard to improve on that.

I"ve seen them run the course in match rifles for highpower. Worked just fine. Didn't do anything overly astounding. If it floats your boat thats fine, if not, you've not lost anything. Much like my continued use of moly in match ammo. Works for me but nothing extreme, I'm just too lazy to clean after every match....

Jeff

Mine haul azz period.There's another poster who has the same barrels that do the samething.You armchair quaterbacks make me laugh.You don't own one most likely but are experts.Next year you'll own one and it will be the cats azz.

Less bearing surface =less pressure=more powder=higher obtained velocity.Buddy with the powder blow by saying less vel is just another person who knows zip about these barrels talking just to hear himself..............so laffin.

S&W has opted to use the gain twist concept in their .460 XVR revolver, and with how well that gun shoots, who could argue with their success?

IIRC this was a measure (one of many in the .500 and .460 S&W's) to control the effects of rifling/bullet induced torque in these revolvers and wasn't intended as an accuracy or velocity enhancement. Among other things the first experimental .500's generated so much torque in the wrong direction that the barrel shrouds were coming unscrewed.

Just a bit of info for what it is worth.. IIRC the old Italian Carcano rifles were gain twisted too.

7
Have some 3 groove barrels here, not gain twisted, that net up close to 170 fps over and above standard barrels.... Not sure the Gain does it, but one can find advantages if they look long enough. So far the 3 groove issue has been repeatable to me, but I"ve only rebarreled them like 5-6 tubes so far.

JEff

Let's assume for a second that gain twist barrels are the best thing since sliced bread. Does it require a certain barrel length to work it's magic ? The 460 for example, would a short barrel snubby make the gain twist advantage negligible when compared to the conventional twist ?

I have a Pac-Nor "accident" that turned out to be a gain-twist. Curious, Big Chris sent the .257" barrel to Barrel-Scan Inc. and the chart says that the twist rate is completely linear from end to end; the twist rate is 1-11" at the breech and 1-9" at the muzzle.

Big Chris wanted to see how it shot, so I ended up with it.

Please be clear, this is a "sample of one." Having said that, this is the fastest, most untempramental, most accurate .25-'06 barrel I've ever shot.

The gain-twist Pac-Nor especially favors 100 Ballistics and runs them at warp-speed. I don't dare publish the top loads because they would without doubt be insafe in most other barrels. I'm not particularly pushing it; extraction is easy and cases last for-friggin'-ever.

I've prolly killed a dozen or so antelope with the barrel, plus a few little-bitty Alberta whitetail and mules <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />, and it's a one-shot/one-kill situation. I've even killed a bigger animal (again, with a single shot) that I dare not write about. Man, it slams furry creatures to the ground bang-flop.

No doubt, another identical barrel would be a slug, but mine is a true winner.

Steve

Thanks Steve
.Your results mirror mine.I'm the same as loads are concerned they are so much over it's dangerous to a common barrel.

Back in college I knew a fella who worked at Apex Barrel in Flagstaff, AZ.

This is how he explained the gain twist concept to me:

The initial engraving of a bullet with a slow twist rifling allowed more velocity at the same average pressure as compared with a load developed with conventional (faster initial twist) rifling. In addition, as the bullet travelled down the barrel and was progressively spun to a faster speed, the gain twist resulted in more area under the pressure curve as compared with conventional rifling with how it becomes "harder" for the bullet to leave the barrel, relatively speaking, thus resulting in a stabilized bullet with higher velocity at the same peak pressure.

All the gain twist does, essentially, is increase the area under the pressure curve, resulting in increased velocity compared to an equivalent load in a conventially rifled bore at the same peak pressure.

I never could afford a new barrel on my college budget at the time so I couldn't actually try one out.

BTW Apex barrels were cut rifled. I don't think it is possible to make a gain twist barrel with the button method.

Jason

Here's what Lilja barrels has to say.
www.riflebarrels.com/articles/barrel_making/details_of_accuracy.htm
Mike

Muzzle velocity is the integral of net force/mass * time. Net force is (the area of a cross-section of the bullet*pressure) - friction. Bullet mass is constant during acceleration. That's very well settled basic physics.

I have a hard time imagining where in that equation gain twist would make a difference in velocity. Where does the extra energy come from?

Mine are plenty accurate.Ain't talking about what it shoots into a inch.My first posts states they can be tricky to load for.I'm talking speed man speed.

You're burning more powder to get to the same peak pressure.

The angular momentum of a bullet carries about 1/2% of the total energy of the bullet.

Has anyone ever made measurements to support the notion that gain twist rifling actually produces more area under the curve? So little of the bullet's energy is in angular momentum, that I have difficulty imagining how such a minor change in how that angular momentum is acquired would make any large difference in total energy.

How do we know that the difference is not simply from tighter chambers and higher peak pressures?

Did not Roy Weatherby go with a long freebore to reduce inital peak pressure when the bullet hits the rifling?

Just curious, because the explantion that a gain twist reduces pressure peak pressure at the same point (inital contact with the rifling) seems to reasonable.

If I were manufacturing a lot of rifles (like Roy did) I would probably choose the (presumably) easier manufacturing method -- the freebore.

Just thinking out loud.

BMT

Therein lies the crux of the issue. I have never experimented with a gain twist barrel, nor do I know of anyone who has invested the time and money into pressure testing barrels of any known quantity.

As an aside...isn't there some friction reduction too? The bullet is spinning less in total as it traverses the length of the bore in the gain twist barrel. How much energy savings from this? Combined with the energy saved from imparting initial angular momentum, would it be enough to make a 100 FPS difference in velocity?

Say you have a 100 gr bullet at 3000 FPS...thats 1963 ft-lbs. Add 100 FPS and you have 2096 ft-lbs. A 6.7% difference in energy. Plausible?

At the 2005 SHOT show I had a conversation with the project manager of the .460 XVR. He informed me that the reason for the gain twist was to keep bullets from skipping the rifling�I�ll have to take his word for it.

I don't see how there would be. There is angular inertia that has to be overcome, and you are just choosing a different place to overcome that. I don't think there is any effect on friction. Friction is just the force (bullet pressing against barrel) times coefficient of friction. I don't think twist rate has any effect.



It doesn't seem so to me, but I was wrong once before. <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

We know that higher pressure will create higher speeds. We do not know whether gain twist rifling does any such thing. So far, the explanation requiring the fewest assumptions is the pressure explanation. If someone takes the time to do the pressure measurements, maybe we will get a definitive answer.

I guess one way to phrase my question is this: Is there any known difference in muzzle velocity between a 1:10 twist and a 1:12 twist, all other factors equal? If not, then why would there be any difference in muzzle velocity in a barrel that transitions from one to the other?

Well, for better or worse Harry Pope's rifles used a gain twist. Whether that's why they held records that stood for decades or not, who knows?

I believe that was the original 1891 versions. I'm thinking the gain twist in that case was intended to solve some throat erosion issues but I may be completely mis-remembering this.

I had a gain twist barrel once. In the late 1990s Steve Webb of Apex made me one--cut rifled. It started with straight rifling and ended up in the 1x9 range. It was chambered in 338 Win mag.

I talked a lot with Pat Eddinger who had tested a few of Steve's gain-twist barrels. The one that started with straight rifling was the "radical" gain twist. The other option was one that started with some twist vs straight rifling.

The idea was the initial area of straight rifling would reduce resistance and allow the bullet to accelerate more quickly. The problems with the radical gain twist were the stress it put on the bullet as the twist increased. Pat said Barnes X bullets did not work in this type of gain twist because they would shed copper as the twist increased. A conventional bullet supposedly has enough flex between the core and the jacket to allow it to accelerate in a gain twist barrel without deforming the bullet.

What really sold me was when Pat shot a gain twisted 416 Rem. It would shoot factory ammo at 2500 fps, which is 100 fps more than published.

Well, my 338 Win with the radical gain twist didn't shoot any faster than a regular 388 Win. It's accuracy wasn't any different either. I finally gave up and got rid of the rifle.

Interestingly, both my current and my last 416 Rems with conventionally rifled barrels shoot factory ammo at 2500+ fps.

I am not sure the gain twist is the magic, just like I am not sure there is anything special about 3 grooves vs 6. I think the idiosyncracies of the individual barrel have more to do with increased velocity than gain twist. If I were going to try another gain twist I'd not go with the radical version.

And no, my 1K BR rifle does not have a gain twist barrel,and neither does anyone else's rifle on the line--though mine is a 3-groover. I can promise you if gain twist barrels consistently added 100-200 fps and shot well we'd all have them.

FWIW I just went into my old reloading records to try and get some comparisons on velocity. I've had two 338 Jamisons, one with the uniform twist @1:10 and the other which I still have, a gain twist supposedly started at 1:16 and went out at 1:11. How he could be that precise I don't know and I doubt he can. Both barrels were 21", as they were in all the rifles I had in those cartridges.

I could quickly only get my hands on one load combination using the same powder and the same bullets in a uniform twist 338WSM and the gain twist 338 Jamison. Both rifles had 21" barrels. The water capacity of the two cases was within 2g of each other, the Jamison using a RWS case having capacity of 81g and the WSM WW case a capacity of 82g. The rifles both weighed just a tad over 7#.

Using a 210 Nosler Partition fired over an Oehler 35P and Hunter as the propellant, they both used 72g of powder for average velocity of 2845 fps out of the Jamison and out of 1:10 Pac-Nor averaged 2860 fps. One grain more @73g indicates the bolt was heavy for both.

My loading record doesn't tell the ambient temperatures at which these were shot, but my recollection of virtually every combination of powders and bullets I tried was that they shot the same in similar conditions. While I have a Pressure Trace setup now and still have the Jamison, unfortunately I sold my last 338 WSM a couple of months ago so I can't make any direct comparison with that system.

At least in my case there wasn't a nickels worth of difference in velocity and they were both about equal in accuracy average just under MOA with preferred loads.

My 30 cal is 1 to 30 ending at 1 to 10.The 7 is 1 to 30 ending at 1 to 9.Both of mine are fast movers.

I am personally familiar with two rifles that use gain twist barrels, both from Ron Smith.

Certainly realize that a sample of two is not statistically significant, however both rifles get well above average velocities.

A good friend of mine had a Husqvarna in 7mm Rem Mag rebored by Ron to 358 Norma. The rifle gets just under 3000 fps with 250 gr bullets and 70 gr of 4350. I have had five 358 NMs over the past forty years and none of them have ever come close to that.

Ted

Steve....Pac-Nor was involved in making gain-twist barrels for a short time but as I understand it there was a liscensing problem with the equipment so he stopped.

I have two of the barrels he made in 30-caliber. Barrels are both 24" long and have an initial twist-rate of 50-1 and end up at the muzzle with a twist-rate of 10-1. One is still a blank but the other was contoured and chambered in 7.82 Lazzeroni Patriot and like you I have found it rather easy to exceed expected velocities across the board .... and I've found that while it really shoots the 165gr, 180gr and 300gr bullets exceptionally well it will even do a "good" job using 130gr bullets lauched at substantial velocities..... haven't shot anything with the 130gr yet but I suspect it will be destructive. My 24" barrel will run a 165gr Nosler Partition faster than a 26" barreled Weatherby I've seen ---- at least over my Oehler chronograph. I haven't done a lot of work on the heavier bullets but I suspect they will also outshine a "Roy".

There isn't any free-lunch as you do need to add more powder but the lower pressures you get with the slower twist-rate near the chamber allow you to get away with this without spiking pressures.

The only thing about the barrel is that while it doesn't foul very much (very, very smooth interior finish) but when you run a rod thru it the rod tends to "skip" and not follow the grooves/lands.

Well, so far we have a lot of posters who notice no difference, some who talk of a velocity increase but don't tell us what it is, and one grammatically-challenged poster who talks of a 200 fps improvement.

Here's the nail in the gain-twist coffin.

Since around 1900 shooters have competed in 1000 yard matches at Camp Perry. They have included some of the best shooters in the world. They have included some of the best experts, like Homer Powley, Father of American Ballistics. They have gone from big magnums down to 6.5-284s and even won one long-range championship in 2004 with a 6mmXC.

If there were the SLIGHTEST MEASURABLE improvement available in velocity from gain-twist, they would use it because extra velocity helps wind deflection and just one shot 1/2 inch farther out can cost these guys the match.

They don't use gain twist.

When David Tubb set out to design the best possible match rifle for ranges from 200 to 600 and sometimes 1000 yards, he spared no expense. His "mass produced" rifle pushes $5,000 with sights. He didn't use a gain-twist barrel.

I think that nails it.

Another poster asked if there were any velocity difference between 10" and 12" twists. There should be if gain twist works. There isn't. It doesn't.

Those who think, based on a sample of one or two, that their gain-twist produces 100 fps or so extra velocity are merely experiencing the normal variations from barrel to barrel.

How is that?

because the elapsed time between muzzle and target is shorter, and therefore is exposed to wind drift for a lesser time.

And if anyone wants to experiment with one, I have a RKS gain twist barrel in 284 chambered and fitted for a Sako L579 with low low miles.

Your 4th and way long better punt.It's funny a respected gunwriter experience mirrors mine but as owners were wrong.

This isn't worthy of any more of my time.Go read some more books.I hear Tubb got a new one.......laffin

I've had two Ron Smith 338 barrel with std 10" twists, and a friend has another. All three had no problem getting full ballistics and were accurate. The gain-twist 284 barrel was accurate but did not show any greater velocities than expected from a 22" 284 Win, and I loaded it to where I was getting definite pressure signs (compressed loads of RL19 and 4831 with a drop tube), so it wasn't a matter of underloading. IIRC it was 1:20 to 1:9

DB,

The article I wrote on the .25-'06 is dated April 1995. Considering the lag in publishing in a quarterly magazine and fitting the barrel, Chris probably made my barrel sometime in 1993.

I had a 700 custom in .338-06 Ackley that was made by a kinda-famous gunsmith in South Carolina that was generally screwed up. I forget who called me, Darrell Holland or Chris, but the barrel was gratis, just to see how it shot.

The story I got is that the barrel was a mistake; somehow it turned out to be a gain-twist. When Chris discovered it, he sent it to Barrel-Scan Inc. and the twist-rate was absolutely linear, starting with 1:11" at the breech and ending with 1:9" at the muzzle. I still have the Barrel Scan chart and it is just a perfect straight line.

When I wrote the article, I didn't get all tangled up in the gain-twist thing. I simply wrote it as full-feature (5,000 words) .25-'06 article; Neidner and all.

A couple of years later, I met Chris in Brusett, Montana; he was coming out from hunting deer and I was going in (he shot a bonzo whitetail). I mentioned that the gain-twist Pac-Nor was shooting up a storm and was one of my favorite rifles.

He told me (again) that the barrel was a total mistake, basically a gear malfunction, and that he was delighted that it shot so well. He commented further that "I could not make another like that one if I tried, but it turned out so darned well that I wanted to know how it shot."

He told me at the time that he had since gotten the gear to (purposely) cut gain-twist barrels and was going to start production in the not-to-distant future. I believe it is these "production" barrels that you are talking about.

I really don't have a dog in this fight. I've only shot a single gain-twist barrel, my "mistake" Pac-Nor .25-'06, and it is phenomenal.

In my experience, there are two types of barrels; boy barrels and girl barrels. The girl barrels are picky and bitchy; they whine and moan and are totally pissed if you don't give them the exact perfect load. Boy barrels are calm and easy to get along with; shooting most loads at least acceptably and many loads in a superb fashion.

My Pac-Nor gain-twist .25-'06 barrel is definitely a boy barrel.

Steve

Wind drift does not depend on the time of flight. It is a function of the velocity lost. That is why it is related to the
Ballistic Coefficient.
Good luck!

Thanks for bringing that up Hawkins. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />

Hawkins,

Can you tell me how to get Sierra to correct their ballistic charts for me. The charts in the back of the Sierra loading manual show wind drift and muzzle velocity inversely related with the same bullet.

I am sure it must be a mistake on Sierra's part. Being a customer oriented company, I am sure they would reprint the tables correctly if only they knew the facts.

Mebbe our friends at Hornady will do that for us?

Indy,

The nail in the coffin--if there is one--for gain twist would be 1000 yd BR. The accuracy requirements of 1K BR are significantly greater than the accuracy requirements for Camp Perry and High Power style shooting.

Idaho Shooter; Bullet drop depends on the time of flight.
Bullet drift depends on the velocity lost. As drag depends on velocity there would be a correlation. sort of like saying the
trees moving make the wind blow.
Good luck!

I, for one, would love to see some pressure testing of gain twist barrels to see the difference, if there is any.

+1
That would be interesting...

More precisely, according to the Krtizinger formula, wind drift is proportional to the extra flight time induced by air resistance and velocity loss.

Wind drift = wind speed perpendicular to the trajectory x (flight time - distance/muzzle velocity)

Naturally, the flight time will depend on the ballistic coefficient of the bullet, which is itself dependant on is aerodynamics and its sectionnal density.

According the the RSI Shooting Lab, a 6.5mm 120 grain projectile that starts at 3200 fps will experience 14.6" of deflection at 500 yards, with a 10 mph crosswind. At 2800 fps, it will experience 17.71" of deflection at the same distance.

What in the world are you guys saying about wind drift,BC, and velocity? All I know is that the same bullet driven at higher velocity drifts less at a given yardage than when started off slower.

OK, Denton beat me to the obvious. Hornady agrees.

As does Sierra.

Wind drift is dependent upon time of flight which is determined by muzzle velocity and ballistic coefficient. Both factor highly into the determination.

I just spent a bit more time with the reloading manuals and the wind drift formula.

Wind drift is a product of the side wind velocity vector multiplied by lag time. Lag time is actual time of flight minus a theoretical value derived by muzzle velocity multiplied by distance traveled. (as Deersmeller already told us)

Lag time is dependent upon muzzle velocity as well as BC, therefor so is wind drift.

I still do not quite agree with the theory in totality, and perhaps
Denton can help us out here as he is a much better mathematician than I. But Sierra assures us the formula is close enough for the purposes we use it for.

If this formula was exactly theoretically correct, then there would be no drift correction required for a projectile upon which thrust was continually applied so that there was no deceleration in flight and therefor zero lagtime.

But we know that rockets in flight and aircraft do have to make corrections for wind deflection, so obviously a wind drift formula totally dependent upon lag time is only an approximation.

For the most part, wind drift does not come about from wind blowing the projectile off course. It comes about because the bullet faces the direction of least resistance, which is the vector sum of the crosswind and the "wind" that the bullet experiences by moving through the air. The bullet is not facing exactly forward. The drag vector acting on the bullet is directly out the tail of the bullet, so it has a huge vector component backward, toward the rifle, and a small component across the path of the trajectory. It is this small component of drag that is the main actor in pulling the bullet off trajectory.

So, to figure deflection, you have to know the BC (affects the total amount of drag, and both components), speed of the bullet as a function of position, perform an octuple integration, and perform the lambda gamma transform.

OK, I lied about the octuple integration and the lambda gamma transform thing. But it is still a lot of math.

I just use RSI.

Riemann, Stieltjes, Henstock, Denjoy, Perron, Daniell, or Lebesgue?

mathman

ugh!
Those names bring back bad memories!!

A couple of those are somewhat esoteric even among mathematicians. Which ones did you run into?

mathman

Riemann sums? and have heard of Stieltjes... none of the others.
Those in a class called transport phenomena.
Dealt with heat transfer, mass transport, and diffusion phenomena.
Rather heavy on theory!!

Hi Steve,

I don't know if you're aquainted with Mic McPherson either in person or thru his writings but he has written several aritcles about the potential benefits about gain-twist barrels (the ones he wrote about were not as radical as mine) and included in the articles what he thought produced the benefical effects.

Mic was instrumental in getting the barrels for me but I don't know why he never followed those early articles with further tests as I think that was about the time he became involved with the design of his new case.

He's really a fascinating fellow and the veritable Mother Lode when it comes to reloading and rifles.

Denton,

So how far off course would an SR71 doing 3500 fps for 5,280,000 feet in a fifty mph wind at 70 degrees wind up?

According to the formula, he should arrive directly on target as the lag time is zero.

Just kidding!

As I understand the meat of your post, the nose of the bullet turns with the wind and actually changes the direction of flight of the bullet. Rather than being similar to a yacht slipping sideways in an ocean currant.

Am I correct then in saying a cross wind close to the shooter can well have more effect on a 1000 yd bullet than a crosswind close to the target, even though the bullet is moving much slower when it is close to the target?

Most people who study calculus start with, and most of those finish with, the Riemann integral. The Lebesgue integral is generally considered the heavy hitter though, mostly because of its powerful convergence theorems.

mathman

Mathman,
I will have to look up that Lebesgue integral in my engineering mathematics handbooks(if they have it) sounds interesting!
BTW, I assume you hold an advanced degree in mathematics?

PhD

Deer smeller; What is the difference between "velocity lost", and "extra flight time". Ballistic coefficient is itself a function of velocity loss.
Good Luck!

Here are some "truisms" about 1000 yard prone shooting (and I acknowledge that 1000 yard benchrest groups are smaller, as one poster said).

1. In any cartridge, the bullet with the better BC is less deflected by wind, even if it starts out slower. For instance in 30-06 a 190 grain bullet at 2600 fps is a better choice than a 150 grain bullet at 3000 fps.

2. For any bullet, driving it faster will cause less wind deflection. Starting about the 1920s, someone won the 1000 yard Wimbledon Cup with a 300 H&H Magnum. The 30-06s almost never won it again, even though both rifles shot the same bullets.

3. Wind near the shooter causes more deflection than wind near the target.

Someone else can work out the math.

3. Wind near the shooter causes more deflection than wind near the target.

Ya oughta hear the marines argue you to death on that one!! I totally agree and it can't really be any way though, IMHO

Jeff

It do. Don't confuse drift with deflection. Planes drift, bullets deflect. Deflection is about drag and the quantified offset of the drag vector. Rockets crab into the wind and do not drift, neither do airplanes properly navigated. It's all well and good to look at this matter up at the multi mach level, more educational to look at what happens in the transonic level....where a .22 RF Match bullet(slower) has less drift than a HV bullet(faster).............drag curves are what they are, drag in terms of retardation is higher in absolute values at higher velocities for any given bullet.....

I did not know there were so many! I do remember Riemann being able to handle piecewise continuous functions, but that was long ago in a galaxy far away.

In my circles, "lambda gamma tranform" is an inside joke.

You can enlarge that a bit. A bounded function defined on a bounded interval [a,b] is Riemann integrable if and only if it is a.e. continuous. The "a.e." is mathese for almost everywhere, which is everywhere but on a null set, a set of measure zero.

One reason that the Lebesgue integral is so important is that the monotone and dominated convergence theorems don't hold for the Riemann version. Also the normed linear space of Riemann integrable functions (usual integral norm) is incomplete, and for a variety of reasons complete spaces are where you want to operate.

Generally speaking the Lebesgue integral is an extension of the Riemann integral in that if something is Riemann integrable then it's Lebesgue integrable and the two integrals are identical. It's the convergence theorems and other mathematical goodies that make climbing the somewhat steep hill to technical facility with the Lebesgue integral worthwhile. For example, Lebesgue measure and integration are used to put probability theory on a rigorous footing.

mathman

To get back to the barrels; Gain twist barrels are not commonly used for accuracy competition for a numberof reasons. At the top of the heap is the fact that the top barrel makers don't make gain twist barrels! Now, does this mean they have, as a result of extensive testing, found the uniform twist to be superior? No, it does not. It does mean they have found a properly built uniform twist barrel to perform perfectly well with no apparent shortcomings. If one builds a barrel using a uniform twist and has success with it, he is unlikely to experiment with a gain twist just to see if it will work as well. Those who do build gain twist barrels do so because they believe there is an advantage to the system; or because Harry Pope did it; or because not everyone makes them; or a combination of these. The people who buy them do so for the same reasons. I use a couple because I think they are kind of neat. They don't seem to provide significantly more velocity but I don't really care about an extra 50 or even 100fps even on my long range rifles. It's my belief that you can't outrun the wind but you can outsmart it if you practice enough! The point is, the gain twist barrels are just fine and appear to have no downside just like the uniform twist barrels. The only downside is to the maker who has to set up to make them.
If gain twist barrels do indded give better velocity, it may be due to the better gas seal afforded by the constantly changing pitch. GD

I haven't read all of the thread, so maybe this has been discussed already, but if the gain twist barrels are faster, as some have said, could the extra velocity be due to less friction, at least in the in the early stages of bullet travel?

OK, I see I'm way behind the curve. My thought was that the coefficient of friction might might be less as the angle of the rifling approaches zero degrees relative to the bullet's axis, but you make a good point about 10" vs. 12" rifling. How much velocity difference is there, on average, between the two?

It depends on how far you are shooting, how windy it is, and how predictable the wind is. Out here we constantly have a gusty, quartering tailwind. Very few guys--if any--in my 1K BR club can pick conditions well enough to be competitve. I do know I haven't seen that approach win matches or set records. The shooters who win the most consistently and set the most records are the ones who "run" their shots together as fast as the can. Regardless, an extra 100 fps would indeed be a big enough deal in 1K BR to pursue it. Reading the wind does seem to work a lot better in Highpower than 1K BR, at least for me.



The down side is radical gaint twist (starts with straight rifling) can damage certain bullets as they travel through the bore.

Talk about wind blowing something off course...................

Blaine,
Reading the wind pays dividends regardless of the type of shooting. Having said that I will admit that 1000yd BR is a bit different for a couple of reasons. First, many of the 1000yd BR ranges seem to be set up so you are shooting over a valley so there is a shortage of usable wind flags. In addition, at the 1000yd matches I have attended, the competitors shoot blind. That is, shots are fired with no knowledge of where the previous shot landed so it's hard to determine just what the effect of the wind on a shot might have been.
Now, and again, back to the barrels. While it is true that a radical gain can distort the bullet jacket, it's not an insurmountable problem. I avoid this problem by specifying a gain of not more than 50% usually around a third (ie. 12 in to 8 in.). Looking at recovered bullets, I can see no evidence of significant distortion although it is possible to see the effect of the changing pitch.
I'm quite sure, if Krieger decided he wanted to make gain twist barrels, these barrels would be just as good and would perform just as well as his uniform twist barrels but no better. Since he can sell all the uniform twist barrels he makes he has no reason to make a gain twist. The same is true of the other top makers. The quality of the barrel is the important thing and the established top makers produce proven quality barrels of a given type. The makers of gain twist barrels are lesser known and this is the reason you don't see a bunch of gain twist barrels at various competitions. When a competitor is buying a new barrel and spending 260.00 to 350.00 for it, he's not too inclined to experiment.
I believe two barrels of equal quality will perform much the same from an accuracy standpoint whether uniform or gain twist. Just as a 4 groove barrel will perform the same as a 6 groove. I've not seen any solid evidence of velocity increase although there is plenty of anecdotal evidence to support it. If such exists, I believe it could be due to the better gas seal rather than a change in the pressure curve. GD

I talked to Jack Krieger about this very subject 6 or 8 years back. His take was that he found no appreciable or inherant improvement of gain twist barrels over standard twist barrels. Since good standard twist barrels are easier to make than good gain twist barrels, he makes standard twist barrels.

Jack modified a lot of the original barrel making machines he uses, so if a gain twist was beneficial, I have no doubt that he could set up his machines up to do it. None of the other good Wisconsin barrel makers do it either. Obermeyer, Broughton, Bartlein, all are standard twist.

Fast Ed

So far as I know the only person to ever rise above the fray with gain twist barrels was Harry Pope. I think it significant that he was shooting cast bullets in those guns. Were it possible to make perfectly identical barrels of gain and conventional twist I doubt there would be a measurable difference in performance between the two.

Pope did a few other things in the process of making his barrels that no doubt contributed to his legend but I'm doubtful that his use of gain twist was his advantage.

From what I've read Pope was concerned with distortion of his lead bullets. He believed that an easier start and the gas seal of the tightening twist were beneficial. At least he proved it to himself.
Good luck!

Some tanks and artillery use gain twist. The rub there, of course, is that you're dealing with projectiles of considerable mass and typically with narrow driving bands.