Gain twist in-depth and reloading

[Alaskashooter]

I’d sure like to hear more about gain twist barrels, most specifically pairing them as far as twist pattern to length of barrel and then as to what bullet weights that is going to like. I’ve heard a few people up here in AK mulling the idea around of doing gain twist but general concessis is: “I don’t know which twist or length to do”

 

[Alaskashooter]

And reloading is obviously popular, a head to head of brass companies would be cool to hear more about. Prime being Norma (atleast in the 6.5) brass is pretty awesome and obviously Lapua brass is great. This last episode you mentioned Peterson brass as well. I know a few of us here in AK are playing with Alpha Munitions brass and getting pretty great results.

 

[Lowlight]

Let Bartlein decide, they do it for you.


I feel now that I am using my 5th GT Barrel, that a 1 to 1 is perfect, so, what that means is, for a 6.5 caliber rifle you would use an 8 to 7 twist for a 24" and under barrel length.

For a longer barrel, I would go 3/4 so an 8.25 twist to 7.5

The goal twist wise is, balance speed (MV) and weight, so the fast you go, the lighter twist, so for a 26" barrel you want to be around 7.5 ending twist with an 8 starting point (there about)

But they are figuring 3/4 gain to 1.0 gain in a twist, start where you can shoot lighter bullets like an 8.25 and end for heavies, 7.5.

Just an FYI, the barrel I pulled off the shelf at MHSA is 8.5-7.7 twist for the Tikka

 

[Alaskashooter]

Thanks!

 

[natdscott]

One key item to ponder, and an inflexibility of the gain twist system in certain circumstances, is that final twist rate is clearly dependant on where you cut the barrel blank.

I know, sorta basic, but it bears saying it for clarity.

In an age where so many shooters are so fickle about barrel length and weight, one needs to plan very carefully what length and twist progression they want to run, because bullets that might be stable at 24" finish length might no longer be adequately stable when you decide to cut it down to 20".

SOME of this can be worked around by extending the shank, and cutting more off the breech end of the barrel at setup rather than cutting off the muzzle, but only to a point (for several reasons).

I like to set up a progresive twist so that the heaviest bullet I'd use will be at least at 1.3 to 1.4 stability factor at the final twist at the muzzle, using NORMAL speeds. Generally, you can gain a little speed from a radius-land and progressive twist barrel, but it is not particularly predictable; as usual, you need to rely on the TWIST to get you stability, not speed.

-Nate

 

[Lowlight]

It's a non-issue

You are not seeing a huge variation and they cut from the chamber side. The fact you have a variation in the twist to begin with, the barrel solves the problem you are stating. You do not lose stability, and in fact, it works better with a greater variety of bullet weights.

Twist and Speed work together, the more speed you have the less twist you need. So if you take a 7 Twist 260 and push it very fast you have a lot more negative effects than if you push it a bit slower. Many subscribe to over spinning the bullet for Transonic stability. But over spinning can damage the bullet, so a GT barrel solves this problem.

You're overlaying standard twist philosophy to a GT and it doesn't work that way. I have a several of them, including 13-5.4 (338), 8.4-7.7 (6mm) and a couple of 6.5s, 8.25 to 7.5, 8.5 to 7.7, and even the short 7 twist (not Gain, 20" ) in my Tikka 260. So I am playing with them all

Most people are looking for speed, so you have to balance twist rate because speed and twist risks damaging the bullet

 

[natdscott]

I'm talking about AFTER the barrel is in use, Frank. Prior planning would prevent ALL of my comments above from having an effect. But you know how that goes.

Shortening an aggressively progressive barrel may NOT be a non-issue, and no, I am not applying constant-twist logic to a T-rifle problem. Guys really like to get an MTU and then turn around and hate the MF for how heavy it is.In an age of an uninformed or unmotivated public, calculation of weights and balance points can largely be ignored; later they decide, for that reason or because it's kewl, to cut 4, 6, 8?" inches off the barrel.

So now, where the barrel WAS at a 7.5" finish, maybe you're at 8.2", and the barrel doesn't work as well and BC figures aren't as high as they were. Frank, I'm not saying it WILL make a difference for the end-user, but I am saying it CAN.

I'm well aware of speed versus twist versus bullet jackets. I come from the place of hand-calculating what I want my barrels to do, with what bullets, at what speeds...being that you pre-date the internet, I'm sure you were there, too. I am not 'playing with them all', but I too own GT steel. I like it fine.

I like people to see all the angles of a system, so I try to bring those out when I see them not addressed.

-Nate

 

[Lowlight]

I have not heard of people cutting GT barrels short, but I am cutting aggressively twisted (Standard Twist) barrels short.

There is a real push for over spinning vs using a GT Barrel, and they are over spinning the barrels on top of trying to maintain a high MV. It's what is actually taking place vs hypotheticals. This has been causing issues with accuracy and deforming the bullets too forcing them to change bullet weights to hunt for a solution.

Case in point, the CAG 260 rifle is spun at a 7 Twist but is 24" long. ( They have shorter too) On top of that, they originally wanted to use a 130gr bullet. This aggressive twist with a high MV forced them to find a different bullet. They had to solve two problems, bullet weight, and jacket thickness because a 130gr grain bullet going 2900+ out of a 7 twist barrel does not work. So they went to a 136gr Scenar. Berger vs Lapua in terms of jacket tech to fix the deformation problems that can happen.

Example number two, the 300NM being spun at an 8 Twist. Most would have stuck to a 10 Twist, maybe dropping down to a 9 Twist for that transonic stability they are looking for, but an 8 twist caused a problem with accuracy. My 300NM is a 1-10 and shoots sub 1/2 MOA at 100 and carries out accuracy to 2500 yards. (Farthest I have shot it) Fast forward to SHOT and a bunch of people pulls me to the side to tell me the guns are not shooting right. Well, of course, a 27" barrel with a high MV using an 8 twist barrel is a recipe for failure.

In the 5.56 world of GT Barrels, they are going 13 to 6 twist, something we have found not to work well in the larger calibers. Beyond solids that is, those bullets can handle the big variation.

Can you mess a twist up cutting it short, sure, but in those cases I recommend a standard twist of a more aggressive type, like my 20" 1-7 twist 260. I managed a handload to give me 2850fps using a 136gr Scenar and it increased my BC by a wide, read noticeable measure.

If you look at the Jim Boatright stuff, Hyper- Stability article, he is recommending solids but looking at a 6 twist rate for them, if you back that off a bit for jacketed bullets, you can get the same results.

But all the data being used is saying they want more spin at Transonic ranges, as spin does not bleed off like MV. So by hyper spinning the bullets, you get increased stability and range.

I recommend staying longer with a GT Barrel and if you want to go short use a fast standard twist. The GT helps balance the extra speed without risking bullet damage.

If you look at this image from Dave Tooley, this is what happens when you go aggressive

Off center and tearing the jackets to spill out the lead

 

[EmanP]

The question is what barrel makers actually offer gain twist barrels or Left hand twists? I know Proof doesn't.

By the way, If someone could get a new GT barrel and only be out $300 with a 10 day wait, we'd all have new barrels on our Tikka's. Stupid slow ass barrels.

 

[Lowlight]

Bartlein,

Mark Chanlynn barrels are left hand just not gain.

Bartlein are the best -computer controlled rifling machines, very precise

 

[natdscott]

I have a CM left, gain, 5R .218/.224.

Only. Only. Bartlein will even listen to such a request.

 

[bobke]

Know this conversation is all directed at bolt rifles, but the prospect of a 22” 6.5 CM with +2 gas and a left or right 8.5-7.7 Bartlein is kind of interesting. Is that a waste of energy or a real possibility? Not heard of anyone going GT in a semi yet. Shoot left handed, so any benefit to LH/GT or stick to RH, regardless of platform?

 

[Lowlight]

It's worth it,

The majority of us should be using a LH GT Barrel, it's the old = new evolution in barrels if you think about. Now with computer controlled CNC Rifling Machines, they can do it just as easy as a standard twist barrel and it has benefits.

The reason they stopped doing them was automation, but now that technology has caught back up, we should be revisiting this at length

 

[bobke]

So...when I’ve a couple of conventional 1:8 Bartleins made up in 6.5 Grendel and Creedmoor, gunsmith requested 1.25” blanks to contour as I spec’d. Would Bartlein stock full diameter blanks, only pre-contoured barrels or would this be custom from the get go with GT to 22” finished length. And to comments above, some people’s definition of barrel length begins from cartridge base forward and others from basically chamber or rifling forward-seems this would require very specific instructions to both parties to avoid cutting the GT short. Make sense?

 

[natdscott]

Not heard of anyone going GT in a semi yet.

You have now.

 

[bobke]

Sounds like a call to Bartlein in order. Thx.

 

[cro789]

I under stand about the left hand twist. So here is my question. I am looking to do a 6.5 creedmoor in a gain twist for a Desert Tech SARS A1 at 23" . Will this length work for the twist of 8.5 t0 7.5 or should I go with a straight 8 twist?

Frank I know you like the 260 a lot. I am looking for less recoil of the creed but is it that much lees than the 260? I have not shot either one only a lot of .308 thats the reason for this question.

 

[Alaskashooter]

I under stand about the left hand twist. So here is my question. I am looking to do a 6.5 creedmoor in a gain twist for a Desert Tech SARS A1 at 23" . Will this length work for the twist of 8.5 t0 7.5 or should I go with a straight 8 twist?

Frank I know you like the 260 a lot. I am looking for less recoil of the creed but is it that much lees than the 260? I have not shot either one only a lot of .308 thats the reason for this question.

Im not frank but your not going to notice a difference between 6.5 creed and 260 rem

 

[j741]

Example number two, the 300NM being spun at an 8 Twist. Most would have stuck to a 10 Twist, maybe dropping down to a 9 Twist for that transonic stability they are looking for, but an 8 twist caused a problem with accuracy. My 300NM is a 1-10 and shoots sub 1/2 MOA at 100 and carries out accuracy to 2500 yards. (Farthest I have shot it) Fast forward to SHOT and a bunch of people pulls me to the side to tell me the guns are not shooting right. Well, of course, a 27" barrel with a high MV using an 8 twist barrel is a recipe for failure.

OK, I'm going to preface this with stating that I'm still a complete newb for barrels/twist/etc.

That said, I've got the idea in my head too have a 300NM. I'd been looking at the Christensen MPR in 300NM but heard some folks having accuracy issues with just the 6.5 version so I'd bcome a bit less sold on it. Then, I see this post from you and think that the MPR is a 26" 8 twist barrel. Almost exactly what you describe as a recipe for failure. So, based on those specs alone, I'd take it your view would be avoiding the MPR.

Also, this article refers to a 26" 8 twist in its praise of the 300NM. That seems to not be the recipe for failure in that instance at lkeast.

I want a rifle for larger game and longer distance (300-600 yd) hunting and occasional long distance target shooter. Looking to use the 230gr hybrid bergers mostly. From what I'm reading here I starting to think maybe my idea of just going with custom build may be better, possibly with a 26" LH GT barrel on it.

 

[AR10ShooterinNC]

In a 223 with a 24 inch barrel, why not a1-14 to 1-7 gain twist?

 

[bjay]

OK, I'm going to preface this with stating that I'm still a complete newb for barrels/twist/etc.

That said, I've got the idea in my head too have a 300NM. I'd been looking at the Christensen MPR in 300NM but heard some folks having accuracy issues with just the 6.5 version so I'd bcome a bit less sold on it. Then, I see this post from you and think that the MPR is a 26" 8 twist barrel. Almost exactly what you describe as a recipe for failure. So, based on those specs alone, I'd take it your view would be avoiding the MPR.

Also, this article refers to a 26" 8 twist in its praise of the 300NM. That seems to not be the recipe for failure in that instance at lkeast.

I want a rifle for larger game and longer distance (300-600 yd) hunting and occasional long distance target shooter. Looking to use the 230gr hybrid bergers mostly. From what I'm reading here I starting to think maybe my idea of just going with custom build may be better, possibly with a 26" LH GT barrel on it.

I understand 8 or even 1.7:8 twist for slower 30 cal like 308.and thats is why blackout300 uses very aggressive twist for 220grainer..thats how it works but for 300 nm's energy? I dunno about 8 twist or faster.when i ordered my gain twist for 230smk or hyb..id to make sure from mark at bartlein that 8.5 wont be too fast..he said he would not recommend faster tha 8.5 for 230s

 

[j741]

I understand 8 or even 1.7:8 twist for slower 30 cal like 308.and thats is why blackout300 uses very aggressive twist for 220grainer..thats how it works but for 300 nm's energy? I dunno about 8 twist or faster.when i ordered my gain twist for 230smk or hyb..id to make sure from mark at bartlein that 8.5 wont be too fast..he said he would not recommend faster tha 8.5 for 230s

Interesting. The Berger calculator didn't indicate any issues with it the 230 hybrid in an 8 twist barrel.

I do have the option of bailing on the MPR and just building up a 300NM on a Deviant action instead. Then I could go with a Bartlein barrel. Although I do like the idea of a CF barrel.

 

[bjay]

Interesting. The Berger calculator didn't indicate any issues with it the 230 hybrid in an 8 twist barrel.

I do have the option of bailing on the MPR and just building up a 300NM on a Deviant action instead. Then I could go with a Bartlein barrel. Although I do like the idea of a CF barrel.

Just received this

 

[oakfig]

 

[Chetly78]

After listening to the podcast, I had the same question as @bobke. Left handed shooter with a 6.5 Creedmoor AR. Not sure I'm good enough of a shooter to tell the difference but its always fun to read and learn things.