Progress Report on Krieger Gain Twist Barrels - NOTHING BUT POSITIVE!!!

L

LBRUNO

New member
I shot a gain twist 14.2-13.4 at NBRSA Nationals in the Unlimited and was winning the event until I dumped powder in my chamber on about the 5th or 6th match and shot a mid 3. This kept me from winning the 100yds. First 10-shot group was a .138 in match 1.

In practice, 17 groups fired, 13 ones. Unbelievable performance. Last month's registered match in Phoenix, chambered a new 14.2-13.4 on my LV, was winning the morning agg with a mid-1 aggregate including a .074 and I did it again, dumped powder in my chamber and only fired 4 shots for record, thus was penalized and lost the morning agg, however ended up shooting a .188 afternoon agg to win the yardage. This is by far the best shooting barrel I have had on a bag gun in several years. My experience with Krieger Gain Twist barrels has been nothing but positive. I now have orders for over 80 barrels and am still taking orders. First shipment will be delivered hopefully sometime in January. If anyone is interested, please call. They cannot be purchased direct but only thru Bruno's at this time.

It is my feeling that these Krieger Gain Twist barrels have a distinct advantage and seem to flatten out some of the vertical that I have experienced in the past. Groups seem to be very flat when developing loads. However, it will take many more shooters than myself to determine if that is true.

If anyone is wondering why I keep dumping powder, it is because I got a new bullet and it is only seating in my case by .010 of an inch and because of my shooting style when I throw the case into the action the bullet tip sometimes separates from the case, causing my powder problems.
I have since purchased a new reamer.

I will answer any questions on Gain Twists. I am also interested in any comments that you may have. Please comment thru Benchrest Central and I will answer.
Lester Bruno
 
Lester

For us that have to cut our barrels in a specific spot in order to make weight, how does this affect exactly where the gain twist starts and ends. For instance, I have only about 3/4 inch of "straight" left on my barrels to get them down to the 76 ounces that is required with every thing else I use, (ie, tuner). The OAL of the barrel ends up at about 21 1/4 inches.

In other words, is the gain from 14.2 to 13.4 measured for the entire length of the 29 inch blank??

I hope I am phrasing this correctly as to what I mean........jackie
 
Lester ...

What's the theory behind Gain Twist that is purported to promote enhanced accuracy ??? Why such odd numbers 14.2 to 13.4 vice 14.0 to 13.5 ???
 
Jackie

I could be wrong but I'm willing to bet Lester is using most of his blank-(26" or more) on a sraight tube for the rail. The tapered barrel would be another animal of course....

-MP
 
Jackie

I don't know about Krieger, but the Bartlein that I have (14 to 13.25) is computer controlled to have the proper 3/4 inch gain in 22 inches. I had to specify the length when I ordered it. I haven't shot mine yet, but hope to this coming Sat. Good shooting... James
 
Jackie, You asked the question just fine.

If for example you take a barrel that goes from starting at 11 twist at the breech to end up at a 10 twist at the muzzle that is a gain of 1 in the twist. If you are doing a 29" blank that is a gain of .0344 per inch. This is assuming you are cutting a uniform gain over the entire lenght of the barrel blank.

We do ours so if you cut one inch off the muzzle end it will lbe at a 10 twist. If you would cut it off 4" further down from the end (4 times .0344 = .1379). So if you take that same barrel as noted above it would end up at 10.1379 twist.

On the barrels we have done for Tony Boyer and Lou Murdica and others where the barrels had a .75 gain in twist that is .03125 gain in twist per inch over the whole length of the barrel. We also are doing modified LV contours and modified HV contours. These are 24" blanks. You only get to cut the 1" off the muzzle and you still can cut an inch off the breech end. That way your twist is what it is suppose to be.

What twist is better? I tell guys I don't have that magic book. All I know is the twist has to be fast enough at the muzzle to properly stabilize the bullet when it comes out. If memory serves me correctly a .840 length jacket bullet at 3200fps. needs a 14.33 min. twist. So if in Tony's example if he would have had another 1" cut off the muzzle the twist would have ended up at 14.281 and in theory still o.k. Remember weather conditions, shooting at sea level vs. 5000ft. elevation etc....still play a part.

With us cutting the twist in with cnc technology we can give the customer exactly what he wants. A button barrel maker will have a couple of problems. One is the twist is built into the button. The button is going to want to fight itself and if pushed to much the button can shatter or the rifling will even skip. On other barrel makers who are doing cut rifling with a sine bar machine or a hydraulic rifling machine are working with a gear driven system and leader bars. They will be limited to the twist rates of the gears etc...and might not be able to cut a uniform gain over the entire length of the barrel. If the gain is only in the last few or several inches of the barrel you have to be careful of how much you cut off. You could be cutting the gain twist off of the barrel blank. Maybe someone from Krieger could add to this post.

We feel that is why some barrel makers in the past who made gain twist barrels and the gain was not uniform where poor performers maybe?

You cannot ask the bullet to go down the bore of a straight twist and then suddenly have the twist get faster. You are asking the bullet to do things it probably cannot do.

The first customers to ask us for gain twist barrels we're black powder cartridge shooters, rimfire shooters and guys wanting to shoot the lathe turned solid bullets with driving bands on them. The first barrels we made for bench shooters we're Lou Murdica and Tony Boyer.

All of Popes barrels years ago where all uniform in gain to the best of our knowledge.

The uniform gain is like having a mechanical choke but built into the rifling.

The reason Tony's barrels went from a 15 to a 14.25 is because he said he once had a barrel that had a twist very close to this. As close as they could check it. He said it was one of the best shooting barrels he ever had. He asked if we could make a couple of HV for him. We did. He shot the HV gun at Kelbly's in Sept. and won the HV class. We made the rest of the barrels he had on order for his LV gun and rail gun the same way. He won the 4 gun, 3 gun and 2 gun at Phoenix in October. He got 11 hall of fame points just in those two matches. Wayne Campbell came in second in the 4 gun and shot gain twist barrels. There we're others there also.

When Lou tested his rail gun barrel in his tunnel and his barrel went from a 14 to a 13.25 twist he put around or over a 100 rounds thru it in one day. He told me he shot 5 different bullet makers bullets both flat base and boattails. I asked him what his groups where averaging. He said Frank lets put it this way. The worst group was a .120. He took that gun and a couple of others to a match the next weekend. The gain twist barrel averaged a .159 @ 200 yards. I asked Lou to compare the gain twist barrels to the straight twist barrels. Would he say they where 10% better, 20% better etc....he said that if he compared those to the straight 13.5 twist barrels he won the Cactus with this year he said they we're all equal but felt the gain twist barrels we're more forgiving.

Also some of the others things we have noted are that there was speculation that you would have a gas cutting effect on the bullet and would lose velocity. This is not true. The rifling is always putting a fresh bite on the bullet and keeping it sealed in the bore. Lou had no loss in velocity at all.

Also with a 6.5 WSM I chambered and shot for a customer with 155 gr. VLD's and a Palma .308 shooter no problems with velocity or accuracy.

The other theory that I asked Lou about was did he think that the uniform gain in twist would help dampen the harmonics the barrel? Maybe this is why the barrel seems more forgiving? Lou said he never thought of that.

We are making a gain twist barrel for someone right now that goes from 0 to 13.5 twist. Will it work? Don't know to our knowledge it hasn't been done before. Will be interesting though on the results.

This goes back to what I've said for a long time. The more uniform the bore sizes are thru out the length of the barrel, the straighter the blank and the more uniform the twist the more forgiving the barrel is going to be.

Lou has said it best before. These are exciting times for all shooters. There are things more available to shooters now a days than just a few years ago. Different technology that has helped barrel makers, scopes, gunsmiths etc....

Later, Frank
Bartlein Barrels
 
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Gain twist...

Frank:

Thank you for your explaination. I have a good understanding of how to increase the twist with a CNC control.

I have a fundemental understanding on how a Pratt and Witney Sine bar cut rifling machine works. Understanding that there are gears to control the twist and gears to control the pull of the cutter. I would have to assume the speed is varried in the mechanical cut variable twist barrel.

The word of importance in cutting a varriable twist barrel would be "control".

CNC has changed the entire machining world.

I look forward to seeing what the future brings to the barrel world. I forsee barrels for long range to have varible twist so particular bullet weights will be in their most stable flight at both the muzzle and the target.

Keep us informed.

Nat Lambeth
 
Nat, Thanks!

Abintx, Why such odd numbers. For some barrel makers they are stuck with the gears and leader bar combination's.

We can give the customer virtually what he wants. We have done barrels that go from 14 to 13.5 or say 14.25 to 13.75 etc....Again is one twist better than the other? The twist has to be fast enough to stabilize the bullet and a faster twist does not hurt you like some think it might. If you are shooting good ammo, match bullets etc....I error on the faster side than the slower.

Barrels that go from a 15 to 14.25 might do just fine in warmer temperatures but could give problems if you start the match out and the temp. is 40 degrees.

The straight twist barrel that is on my bench gun is 13.75. I built it before we did any bench barrels for anyone. I have to make one for myself and play with it.

Like I said earlier. We did a 6.5 WSM for a F-Class shooter. I chambered it and put it on his gun. Shooting the 155 gr. VLD's at a 100 yards the gun was shooting 1/4 min. groups and is performing just fine also. The palma shooter that we made a .30cal. barrel that went from a 12 to 11 twist he told us he shot the smallest .30cal. groups he has ever shot at 100 yards. He took the gun the next day and benched it a 1000 yards and had the same results. He ordered 3 more barrels just like it.

We have even done a .338 barrel that went from a 14 twist at the breech to a 7 twist at the muzzle to shoot the lathe turned solid bullets. The guy couldn't wait for the bullets anymore to get here from South Africa or Germany so he shot some 300gr. Sierra MK. Barrel is chambered in .338 Lapua. He said at 300 yards it was an honest 1/2 min. gun but it was not built to shoot those bullets in the first place. I expected him to say that 2 would touch and the other 3 rounds would go flying off into no where but the opposite is what happened. He said it wasn't do anything really weird or bad. He said maybe it didn't shoot as well as a straight 9 or 10 twist barrel but couldn't really complain. The 14 to 7 twist is a 2-1 gain.

We just started shipping barrels to the bench shooters in late summer. Like I said the first guys to ask us for them where the black powder cartridge shooters. Shooting guns like the HI Walls, Ballards etc.....

As more get out there and we get more feedback the more we can share with the shooting community.

Later, Frank
 
Great Post, Frank

Thank you for sharing a wealth of info.

I think you are correct in your assessment as to what is really going on with the gain twist. The bullet never gets "loose" in the barrel, there is always a certain tension being exerted against the lands as the bullet travels down the barrel. Sort of like the "anti-backlash" attachment on many milling machine tables and lathe cross slides.

It would be interesting to see a bullet that has been pushed through a gain twist barrel. Especially in that "0 to 13.5". Since the initial engraving on the bullet would be a straight line, and end up in the helex of the 13.5, you should see some evidence, such as the engravings getting narrower, or wider, at a specific point on the bullet. ..........jackie
 
0 to 13.5 Twist Barrel

Jackie,
That 0 to 13.5 Twist Barrel Frank spoke of is the one I ordered and am anxiously awaiting. The Twist will go from 0 to 1:13.5 in 20" Length but not start for the 1st 6" of the Barrel Blank. That will allow me to use my STD 21.8" bbl length and have the throat at 0. The Twist Rate will have just gained to 1:13.5 at the muzzle. Like you observed the Leading Edge of the Land Marks on the Bullet will be canted like a std 1:13.5 twist bbl. The following edge of the land mark will be straight with the bullet axis. (the two edges of each grroove mark won't be parallel)

I think spreading out the rotation acceleration over the entire millisecond the bullet is in the barrel will result in: A) reduced vibration excitation. That would reduce the vibration displacement. B) Less torqueing in the bags. C: R Robinett tells me the reduced rotational shock will be a good thing for the Jacket to Core Bond. (Reduced chance of Core Slippage)

These are only theories but I thought it would be worth a test. When I get it I will run a complete tuner Test with Velocities, POI, Group sizes, & etc. I will post Targets, Data Sheets, and any conclusions on this forum.
Esten Spears
 
Question about 0-13.5 twist..

If
I I read this corectly you are jumping the bullets straight for about 6" then going to 13.5 at 20 inches. My question is the gain twist gradual or instantanious afterthe first 6 inches. Is the bullet continuing to accellerate (spin faster) as it leaves the bore or is it slowing down at the point when it leaves the bore. In principal it sounds kinda like the smooth bore shotguns and rifled screw in chokes.

Rustystud
 
Sorry for the delay. The Krieger Gain Twist varmint barrels will be 27" in length. Approx. the first 6" will have no gain. It will be at whatever twist the barrel starts at. So an adjustment can be made by cutting the major weight off of the straight section which then will not interfere with the gain. There will always be a straight section with the rest of the barrel being a full gain. I have tested a 29" blank by cutting 6" off of the muzzle and 1" off of the breech and the barrel still shot great. It does not seem to affect accuracy no matter which way you cut.
Any other questions please contact me thru benchrest central and I will respond as quickly as I can.

Lester
 
Thanks Frank!

I love my standard twist Bartline barrels, and I can't wait to try out a gain twist.

s.
 
0 to 1:13.5 Bartlein Barrel

Rustystud,
The Throat will be at 0 twist rate but the twist will start increasing within .5" of forward travel. Remember I said the twist starts increasing 6" from the rear of the barrel BLANK and I'll be cutting off the rearmost 4". Then, on a 6PPC, the throat is another 1.75" forward of the boltface (rear edge of the barrel)
 
Gain Twists

We have been doing gain twist on our .308's for 8 years now and the results speak for themselves with all of the guys winning in Hunter Class and VFS matches as well as Ken Livengood and Herb Llewelyn setting world records with them over the last 2 years. We don't put as much gain in our barrels as kreiger or Bartlein we only put about a 1/8" of a twist gain in ours. Mike Rocks theory is that it keeps the bullet from going to sleep as it is traveling down the barrel keeping the bullet against the driving side of the lands. I think everyone will be pleased with the gain twist barrels no matter who's brand of barrel they are using.

Paul Tolvstad
Rock Creek Barrels
 
a gain twist barrel

abintx said:
What's the theory behind Gain Twist that is purported to promote enhanced accuracy ??? Why such odd numbers 14.2 to 13.4 vice 14.0 to 13.5 ???
Click to expand...

puts less "stress" on the bullet by "accelerating" it to terminal rotation rather than jumping there right away. Cmes from the cast bullet era where the gain was a lot more over a longer barrel
 
Wouldn't the gain twist barrel be a bit more of a bugger to lap after rifling? I would imagine after going back and forth in the bore the land impression on the lap would look somewhat like an 'X'. Just curious!
 
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