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

The more of a gain twist yes it is a little harder to lap but not difficult. We've done .338 barrels that went from a 14 to a 7 twist. The lap finish was awesome.

Also we have had some requests from some shooters because we are getting such nice finishes out of the rifler to begin with they didn't want they're particular barrel finished lapped anyways.

With the cnc rifler we don't have a problem with the cutting oil getting hot/heated up from running a hydraulic Pratt rifler that it thins out the cutting oil or worry about a hydraulic leak that contaminates the cutting oil.

We just finished some 20mm barrel (.788 x .817 bore and groove size) blanks that where 45" to 53" long for a couple of different customers. The finish out of reaming was as perfect as could be had. How nice the reamer is made helps also but the finish out of rifling was also very nice. For these barrels we did no prelapping or finish lapping.

Our cutting oil stays room temperature all day long.

The first barrel we made and I tested them all was not finished or prelapped. I wanted to see how the barrel would shoot and foul. I put over 50 rounds in it at one sitting. No break in period etc...just one round after another. My last 5 round group at a 100 yards measured a .191 and backed it up with .250 group at 200 yards. Yes the barrel had fouling in it but the accuracy never went sour. When I went back to the range the next couple of times and started pushing 150 rounds it was cleaning easier and easier.

Later, Frank
Bartlein Barrels
 
Do the bullets come out with a bowtie groove where the rifling engages.

On the breech end, is the rifling parallel but still all the way back to the freebore. IE, you can still have the bullet engaged into the rifling, only the rifling is straight.
 
Haze10, Are you asking is the rifling straight i.e. no twist at all? I think I know what you are asking but not quite sure.

Start loading like you normally do. If you start by having the bullets touch the lands then start there and adjust your bullet seating depth like normal.

In the above examples if we are cutting a .75 gain twist in the barrel the gain on a 24" blank is .03125 per inch and uniform over the whole length of the blank.

I hope this answers your question.

Later, Frank
Bartlein Barrels
 
Interesting

The more I think about this, the more sense it all makes. After all, the only thing, (as far as twist goes), that matters is how fast the bullet is spinning the instant it leaves the barrel, when external ballistics take over.

I would be interested to see exactly how a bullet looks after experiencing a Gain Twist. The initial engravings will always be present, any variation to the "pitch" of the lead will change the width, shape,or something.

Maybe someone with a gain twist could push a lead slug through the barrel, and compare the engravings to an identicle barrel, except for the gain in the twist.

But if the bullets all go into the group, what they look like when they leave the muzzle matters little.

You have to hand it to the people who do Cut Rifled Barrels, especially the guys at Bartlien. Their cnc tool controle proccess allows them to be creative in this sort of thing. Apparently Krieger has come up with a alternative using their mechanicle Rifling Machines.

This is neat stuff..........jackie
 
jackie schmidt said:
The more I think about this, the more sense it all makes. After all, the only thing, (as far as twist goes), that matters is how fast the bullet is spinning the instant it leaves the barrel, when external ballistics take over.

I would be interested to see exactly how a bullet looks after experiencing a Gain Twist. The initial engravings will always be present, any variation to the "pitch" of the lead will change the width, shape,or something.

Maybe someone with a gain twist could push a lead slug through the barrel, and compare the engravings to an identicle barrel, except for the gain in the twist.

But if the bullets all go into the group, what they look like when they leave the muzzle matters little.

You have to hand it to the people who do Cut Rifled Barrels, especially the guys at Bartlien. Their cnc tool controle proccess allows them to be creative in this sort of thing. Apparently Krieger has come up with a alternative using their mechanicle Rifling Machines.

This is neat stuff..........jackie
Click to expand...

Just to simplify things for observation purposes, imagine a 1-12 twist barrel will have a 30 degree rotation per inch pitch, and if this were to gain twist to 1-10 inches giving a 36 degree rotation per inch pitch, or 6 degree change. Calculate this over a 24 inch length barrel, that would be a 3 degree change gain twist over 24 inches.

All these figures are a slight bit faster than our present BR twist rates, but still in the same ballpark.

Imagine a 2-3 degree variation in engraving twist on our present BR bullets............my guess is that the human eye would have a very difficult time in perceiving the difference, and if it could it would probably show up as a slightly wider land width engraving................Don
 
My $0.02 is y'all will have to come up with a better explanation than the "less stress on the bullet" one. We already spin 6mm bullets out of an 8-twist barrel, and the slight difference in grouping compared to, say, a 14-twist, is explained by the other parameters.

Not to say that these slight gain-twist barrels won't show an improvement on the target, but I'd need a much larger sample size to keep from thinking that they are this winter's "density altitude" phenomena.
 
Let me elaborate:
1) Remember the Oswald magic bullet, or any bullet fired from conventional rifling into something soft that doesn't deform the bullet. When you look at the bullet, the rifling is impressed into the bullet. The width and angular twist of the barrel matches the bullet perfectly. Once the bullet engages the rifling, one revolution or ten, the rifling groove in the bullet doesn't change because it is perfectly symetrical for its entire length down the barrel.

With the gain twist, the angular twist angle is changing. So the bullet, passing down the barrel, would have the rifling deform a groove into the bullet, but since the angle of the rifling is increasing, the front portion of the bullet would be pushing into the increasing angle rifle groove, and the read portion of the bullet would be pushing away from the rifling groove. If the pristine bullet was recovered after firing, the rifling grooves on the bullet, front and rear, would be wider than the actual groove of rifling of the barrel. The only point at which the rifle barrel groove would be the exact width of the groove on the bullet, is at the bullets geometric center. The impressed groove on the bullet would look like a bowtie. At least this is what I read about being the issue with bullets in gain twist having poor sealing. No idea if any of this is true.

2) You mentioned that the rifling was straight for the first 6 inches, or that you could request it to be straight and then increase at the muzzle to your final twist rate, say 1:8. My question is to define this more. After the barrel is chamber cut, and the smooth side wall of the freebore is cut in, are you saying that the rifling, althought with no twist whatsoever, starts at the end of the freebore, and then is dead straight for 6 inches before the twist begins. For a reloader, you can still seat the bullets to engage the rifling. I'm just thinking this would cut a straight rifle groove in the bullet, and the bullet leaving will be cut with a 1:8 twist. So that bowtie effect will be quite evident. Thats if I understood you correctly.
 
Bartlein 0 to 13.5 Twist 6PPC Barrel

Haze,
I may have confused you with the 6" zero twist rate section. The 6" is just the amount to be cut off the barrel blank plus the distance from the end of the finished barrel to the throat. (about 1.75" on a 6PPC)
Just think of it this way; The bullet will be jamed into straight lands (no twist rate) As the bullet travels forward about 20" to the muzzle the twist rate immediately starts a linear increase in twist rate from zero to 1 turn in 13.5" over its 20" travel down the barrel. The total twist will be about 250 degrees with most of it occurring near the muzzle end.

Several have talked about butterfly shaped engraving on the bullet. That is what I will probably get if I push a slug through it. A fired bullet will be different however because of the very high rotational loading thats doing the rotational accaleration on the bullet. ie. the engraving side squish will occur on one side. The bullet engraving is probably not that important but it could be a slight advantage. Most experts agree that you wouldn't want the muzzle at a loose spot in the barrel. I think the constant rotational acceleration coupled with the engraving side squish would prevent the bullet from getting loose in the barrel even if the diameter opened up several tenths.

Someone said they thought the core to jacket slippage advantage was meaningless. I have no experience in this area but in my conversation with Bullitmaker Randy Robinette; He thought it could be a significant advantage. Also Harold Vaughn talks about it in his book.

Looking forward to testing it.
Esten Spears
 
A few things to add.

One to Jackie! Thanks for the compliment!

Fred J. We have made some .22RF in gain twist. The first one went on a guys BR50 gun (don't know what class he shot it in) and the first match he took it to he won his class with it. Also just found out from a shooter in Australia last week that got a few of our RF barrels (not gain twist but straight 16 twist for him) and him and his wife came in 1st and 3rd places and also set a new Australian record in the process for they're state championships.

Haze10, To answer your question about the bullet getting a gas cutting effect and not sealing in the bore and losing velocity is not true. Lou Murdica gave me his loads and data and he lost no velocity at all over a straight twist barrel. The rifling is always putting a fresh bite on the bullet as it goes down the bore. There for it is keeping the seal so to speak. This was a concern by another really good bench shooter who was here at our shop earlier this year. We didn't have any data at that time. Nobody has gained any velocity but they haven't loss any either. Also a really good customer and shooting buddy who we made a .30cal. Palma barrel for reported the same thing to me. We also made a 6.5 barrel that I chambered up for a F-Class shooter in 6.5WSM and he is shooting 155gr. VLD bullets thru it. At the range the gun shot great and over my 35P chronograph was getting great velocities with out any load development at all.

Charles E, Yes I do agree that more need to get out there and data collected. So far though looking at the 6pcs. we've made Tony, the barrels that we made for Wayne C., Gary Ocock, Lou Murdica and some others there have been no real negatives from anyone. Again I tell guys though that what twist combination for a given caliber and bullet 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.

We are not making any claims that is this the answer to all accuracy problems etc....or it is going to make every barrel a magic barrel. But if it really does help maybe if you buy 10 barrels from a given barrel maker and in the past you would maybe get 6 that where consider hummers out of the 10 but now that increases to 8 or 9 out of 10 wouldn't that be a bonus to all. So far it doesn't seem to be hurting anyone at all. If the consistency of how accurate a barrel can be is made better than you will see a consistency in the aggs. dropping.

Also the answer is yes. The engraving on the bullet will get wider as it gets toward the muzzle. How much is determined by how much of a gain it has in the barrel. On real radical gain rifling it shows on the finish lap real easy. Also so it would show on the bullet. In a .75 gain twist it is approx. a 1.26 degrees gain. So Don you where in the right area of thinking.

Later, Frank
 
Six out of 10 being hummers -------
Frank, that's pretty optimistic I don't care whose name is on the barrel.
 
Hey Pat! I understand what you are saying. I was just trying to give an idea that if it helps the consistency in getting a better barrel blank then everyone wins. I was just picking numbers and they necessarily didn't represent what the average number is etc....

Later, Frank
 
Gene, I hate to play the devils advocate but I have a story here.. Year before last I built a 6X47 Lapua, this was on a SPF Predator... The only barrel I had on hand was a 10 twist Krieger. The reamer I used to cut the chamber allowed me to use my benchrest bullets which are boattails, btw.. This rifle is getting 3,700fps with those 68 grain boattails and will group under 1/4'' very often.. In fact, I believe I'd bet on it...
 
Gene, I have to agree with Pat.........

............I believe core stripping is a non-issue in short range BR.

When is the last time that anyone witnessed a 6ppc bullet not make it to the target when all the conditions and components are right?

There is a huge difference between a 6mm Remington/68gr. bullet travelling at 4,000fps/300,000 rpm and a 6ppc/68gr. travelling at 3,300fps/220,000 rpm.

Ive seen several bullets not reach the target, most likely to core stripping or simple excessive rpms where the jackets simply could not withstand the extreme centrifical forces. These were always in barrel burners like 6mm/06, .22 chetahs, etc., usually shooting fast twist barrels..........Don
 
Any bad Krieger Gains

The answer is no, i have now chambered a total of 7, i have shot one aggs with all of them, 1 rail and one bag gun have been as close to a hummer as i have ever had. VV-133 has shot the best in most of them however i have not worked with some of the other powders that i usually do.

Lester Bruno
 
Progress report NEW GAIN TWIST KRIEGER RAIL BBL

Chambered a 23" 1.450 gain for my rail, cut 1" off of a 24" blank to simulate a shorter barrel and give me as much of a full gain as possible. I used a new reamer from Kiff for my new bullet die purchased from George Ulrich that I will call the BRUNO UNO bullet. No I am not selling any bullets as of yet. Shot T powder to start in our recent match in Phoenix, switched to 8208, and worked on seating depth at the same time and things went from good to worse, I shot some groups in practice the day before .100, .107, .155 and in the match shot a .120 however I did not feel I was getting consistancy. Last weekend I decided to try VV-N133 so I went up the scale as usual and stoped at 55.5 on my Bruno powder measure ( do not try this load without caution might be too hot for some rifles) 2007 lot. The last 5 groups measured .237 .164 .215. .201 .115 which equals .186 aggregate. Some might think this is not so great but please consider the wind was averaging about 15 to 20 miles an hour and I was shooting in Phoenix. All in all I felt very comfortable with the agg and figured if I was shooting a match I would have been in the top 5 percent at days end. I am going to try to shoot the barrel again this weekend and if i do i will try to post the results. My first shipment should arrive sometime in January, i am taking orders for the second shipment of which i should recieve the end of February or the beginning of March. I must apologize for not answering many of your questions but with the primer, powder, brass, and bullet glut going on as well as building rifles, I am having trouble getting to the computer.

Sincerely

Lester Bruno

Bruno Shooters Supply
 
Gene - radical gain rates

Gene Beggs said:
When Frank Green mentioned his barrels would be available with a twist rate begining with zero and increasing to whatever one specifies at the muzzle, the light came on! "Voila! The answer to core stripping problems!" :D
Click to expand...

Gene, the thing I would be concerned about with such a radical gain would be the bullet engraving process. It's been discussed that with a varying twist, the engraving pattern would be similar to "bow tie", which makes sense as the angle of the lands varies depending on the twist rate at that point.

I notice the bbls being shot with success now have a slight gain, about .75 rev to them and this engraving difference doesn't seem to be issue. I would think going from 0 to 14 or so could be quite a different story. If you try this and find something contrary I'd love to hear about it.

Take care.... Scott
 
Apology

My apologies to Lester Bruno for thoughtlessly bringing up the subject of core stripping on this thread. It was completely off topic.

Sorry Lester, I activated my mouth before putting my brain in gear, :eek:, but I believe the subject of core stripping is so important and is so often overlooked, I thought it wise to start a separate thread on the subject. Pat B., Don and Woody, we will continue our discussion in a separate thread.

Lester, sorry for interrupting. :)

Gene Beggs
 
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