Alternative Twist Barrels (Progessive, LH)

[AIAW]

So I just ordered a Remington MSR (MK21) earlier today. Looking forward to getting this beast out and about. Tangent Theta 5-25x H59 won't be in until February sometime though. Going to pop a S&B 5-25x MSR on it in the mean time.

This is going to be one bad-ass rig. Comes as a 338LM in this case. 300NM is going to be the first custom tube to be spun up for it I believe. Perhaps a 338NM also. I've already got more 300WM and 338LM rifles than I can handle lotting brass for.

I know there are older threads on this topic - I've seen them. Still, curious in this day and time if anyone out there is running a modern left-hand twist precision rifle barrel? I remember Frank doing a video about a progressive left-hand twist barrel, which I'll post also. A progressive twist 300NM would definitely be something to experiment with I think, probably considerably versus LH rifling (or do both too).




Talking with a very reputable barrel maker here earlier today, there are benefits of course but how tenaciously do you have to train yourself to make those windage calls at distance so backwards from what you're accustom to? I know it would be quite a reorientation experience for me personally having shot RH twist for so long. According to some random data, .1 L for Coriolis/Eötvös and .5 L for spin drift (0 MPH wind influence) at 1760 yards (285g A-MAX @ 2810 fps - 1-9.35" twist). Not really a good case example for using LH twist to correct for Coriolis/Eötvös, but .1 MILs at a mile is still 6.4 inches of drift.

.5 MILs @ 1 Mile = 31.7 inches

31.7 inches - 6.4 inches = 25.3 inches. A solid windage improvement none the less, not huge by any means.

I've been curious about the recoil impulse as well, as that would definitely be a bit different as Frank explains in his video.

Don't want to turn this into an ELR external ballistics discussion as it shouldn't be. More so of a benefit (however slight that might be) versus seasoned training topic. I'm not particularly looking for input or data for myself, mainly curious as to the number of people doing this with modern rifles and reasoning.

 

[Precisiondada]

Interesting subject matter, curious as well. Granted, I’m no professional and probably in desperate need of additional training. I am however, in the market for another barrel. Frank’s video certainly makes it seem that right-handed shooters should be using a left-twist barrel.

 

[Lowlight]

I have maybe 4 being run right now, and I have found a host of benefits from it.

Left-Hand Twist:

This is most beneficial for positional shooting. You don't feel it as much in the prone as you do in other positions, but you can feel the difference in recoil, the pulse is more in line with your body and staying on target is easier.

For magnums, the benefit is the reduction of drifts when you shoot extended ranges. That benefit is real but harder to quantify because I believe the books are wrong. I don't see the drifts even shooting at 2k being an issue, I never dial on them, I don't even calculate the drift at all, and I simply dope the wind and my success has been greater than those who "calculate" them. Even at the World Record / ELR events, I have attended I have seen some of the biggest proponents miss by a wide margin on their first shots and listening to them and seeing their adjustments, they are WAY overdoing it.

The 1.5% of the drop is about the closest I have found to work for the drifts, and being going Lefthanded you simply remove it from the equation.

Gain Twist:

So I am running a couple of different GT Barrels from Bartlien and most of the ones I have shot, and I have seen being used are about a 3/4 Gain. That seems to be a sweet spot but upon reflection, I think 1-1 is doable. To translate that, it means I use 8.25 to a 7.5 Twist for a 6.5, I have an 8.4 to 7.75 6mm, etc. But I believe you can do 8.0 to 7.0 and still be okay, vs say an 8.0 to 7.25 which is what Bartlien Recommends.

The unseen benefit I have found is with ammo. The gun doesn't care, it likes them both. The most recent 6.5 LH GT barrel that MHSA spun up for me is hammer accurate and put both my Prime 130s and my McCourt 136gr load in the same exact spot at 100 yards. You cannot tell the difference if I load 10 rounds and alternate between the handloads and the Factory Prime, the group is the same, one hole. They start to deviate around 500 - 600 yards out where the BC of the 136gr load takes over. I can literally bring two bullets and the rifles are zeroed for both.

The idea that I see people mention, where the GT Barrel adds more impressions on the bullet is flat out WRONG. You are not laying across the bullet anymore, in fact, it is better for the bullet because you are not overspinning it from the start. Hornady has shown no issue with Pressure. (Hornady has been testing GT Barrels since I started crowing about them, they won't tell me the results, but they smile) Guys want to over spin the bullets for "TRANSONIC STABILITY" but at the same time, they want to push the bullet as fast as possible. This does not work, dont' believe me, why do you think the 300NM is suddenly not working out for the Army. The rest of the free world knows how to push a heavy 30 Cal, apparently, the Army missed the memo or spoke to the wrong guy. His 20" 300NM over spun is not the same as their 26" 300NM pushed 200fps faster. That moves the lead underneath, throws the bullet out of balance and causes accuracy issues as well as inconsistencies in BC and performance. (Sound Familiar)

A little more gentle on the bullet, still giving you that extra spin, with deforming the lead underneath throwing the balance off.

Bartlien has this down to a science because they use CNC, Computer-based rifling. The Pratt Machines, you know the old school barrel making stuff, only bores the initial holes for them. They have a custom, computer-controlled machines that Tracey Built to do this. They can go 4 decimals places in any direction, at any rate of start and finish, and it works. They do this for Service Rifle because those guys shoot more than one weight of the bullet. They go like 14 to 6 twist for the light bullets up close and the heavies at 1k. The winners have known this, the general public not so much.

I also believe a GT Bartlein has placed in Benchrest too, but don't quote me.

Times are changing, we are learning a lot, and when you don't try to be someone you're not and throw away the idea of making money off this stuff first you find out what works vs trying to sell an agenda. If this did not work I would have bought my last barrel, I can call Bartlein up and get it for nothing if I really wanted too. I bought it from MHSA and paid them to spin it up. This shit works because I ran it like you do. I shot it in the real world, I shot it in Competition. I saw guys at the SH Match with their LH GT Barrels on their AIs and they agreed. I took it beyond a mile and compare as much as possible inside. It's viable, nobody who has followed my lead, and there are a bunch of you, has stepped up to say, I blew it and I was wrong. Everyone sees, or feels a benefit, might not be earth shattering, but a benefit none the less.

I like em,

 

[Precisiondada]

Frank, are you summarizing that all other variables being equal, a right handed shooter would be better served using a left-hand twist barrel?

 

[AIAW]

Damn that is some good info, all of it! Thanks Frank. See, you just can't read this stuff in a book. It takes experience to come to these conclusions - real world proof.

I'm honestly baffled that this hasn't caught on in the precision rifle community. Hell, doesn't even have to be a "precision" rifle. You just rarely ever hear of someone, at minimum, considering LH twist rifling, much less gain-twist.

I understand the complexities involved obviously as to why factory barrels aren't included. I am not one to deal in absolutes when it comes to another man's money, but almost any prospective custom barrel owner should consider one or both of these rifling techniques I would say.

Yeah you had a video a while back with Bartlein that shows their process. Very nice operation they are running there.



I'm definitely going to get a few LH GT barrels spun up for my AI's and this new MSR. Results to follow in the future of course.

 

[samb300]

@AIAW I think you're missing a decimal place in all your windage math.

1 mil at 100 yards = 3.6"

1 mile = 1760 yards

1 mil at 1 mile = 3.6" x 17.6 = 63.4"

So 0.1 mil at 1 mile is 6.4", and 0.5 mil at 1 mile is 31.7". Not exactly the wild difference you're talking about in the OP.

 

[AIAW]

Thanks. Yeah, that's what I get for copying and pasting stuff from notepad. Just a typo, I'll fix that in the original post.

 

[AIAW]

So... like, no one else is planning on implementing any of the above? I'm truly surprised actually. It's even got the HMFIC's seal of approval!

The community will look at a whole range of unique calibers to tweak every bit of deviation out of a platform for their style of shooting but when it comes to essentially the most critical component of the whole system it's just "stick with what's always been around"? To each his own of course.

 

[leftyk82]

I don't have anything to contribute now but I will soon.

I've got a Bartlein LH Gain Twist .308 being spun up by Chad at LRI. Twist of 10 to 9; finishing at 20".

 

[MarkLeupold]

So... like, no one else is planning on implementing any of the above? I'm truly surprised actually. It's even got the HMFIC's seal of approval!

The community will look at a whole range of unique calibers to tweak every bit of deviation out of a platform for their style of shooting but when it comes to essentially the most critical component of the whole system it's just "stick with what's always been around"? To each his own of course.

I've been interested in a LHGT barrel ever since Frank started talking about them. The benefits are there and they are tangible. I'll burn out the barrel I've got and I'll send in for a custom Bartlein well in advance so I'm not down a rifle waiting on the lead time.

 

[ThePretzel]

The guy who placed 2nd overall in the PRS tactical class used a LH twist barrel in his .308 for some of the same reasons that Frank mentioned above. He specifically liked how it kept the muzzle on target better compared to RH twist barrels, which is huge for the positional shooting in PRS.

I would like to order one to try, but when buying a barrel recently I didn't plan far enough in advance to be able to order a custom barrel like that from Bartlein without waiting quite some time where I don't have a functional rifle.

 

[AIAW]

Exactly. If you were a RH shooter you'd automatically pick LH rifling when ordering a custom barrel.

I just don't think the information has gotten out like it should.

 

[Lowlight]

Yes, the benefits for the shooter comes from the LH twist, but also for reducing the drifts in the northern hemisphere

So it's dual use, you have the recoil pulse working for you, and in the case of 1k or beyond you have the cancellation of the drifts against each other.

It's a case of, how we have always done it and for others, it's a machine thing. John Browning's fault as I understand it, mass production meant treating everything like a screw.

Mark Chanlyn here in CO does LH twist and has quietly for a very long time. Just not progressive.

They are out there, just not mentioned much and the cost to switch stuff for people is a bit of a roadblock, which is silly because, they spend money on less beneficial stuff.

 

[GrandpaDeadLegs]

Oh interesting - would a left handed Argentine then have the same argument for using RH ?

 

[Lowlight]

Yes, if you are in Argentina you want a RH Gain Twist to cancel out the drifts, but you lose the benefit of the change in recoil pulse if you are Righthanded.

Most stuff ignores left-handed shooters, there are not enough of them to matter, so most of what we do is based on Righthanded people.

 

[GrandpaDeadLegs]

So... like, no one else is planning on implementing any of the above? I'm truly surprised actually. It's even got the HMFIC's seal of approval!

The community will look at a whole range of unique calibers to tweak every bit of deviation out of a platform for their style of shooting but when it comes to essentially the most critical component of the whole system it's just "stick with what's always been around"? To each his own of course.

The details of the barrel making process are pretty high up on the pyramid! A fella at home has some control over ammunition at least, can form brass easily, etc... and get that into his mind.

It's easy to stop at "that's a barrel made by a quality company" and be happy someone was willing to make your funky wildcat chamber.

Most people out there are happy with "it's a barrel." And nit pick scopes to death

I will be happy to try LH twist on my next rifle - no one in the bear pit has ever accused me of being conservative

 

[LeftyJason]

Yes, if you are in Argentina you want a RH Gain Twist to cancel out the drifts, but you lose the benefit of the change in recoil pulse if you are Righthanded.

Most stuff ignores left-handed shooters, there are not enough of them to matter, so most of what we do is based on Righthanded people.

How about a left handed shooter in North America? Rh twist?

 

[Lowlight]

How about a left handed shooter in North America? Rh twist?

Depends

If you shoot prs yes, if you shoot ELR no

Context, it's all about understanding the pro and cons for each situation.

Positional shooting you want to manage recoil, who cares about drift you are inside 1k.

ELR shooting - recoil don't matter the drifts do

Pick the right tools.

 

[TripleBull]

So... like, no one else is planning on implementing any of the above?

Shortly after buying an AX MC last summer, I had Mile High order me a LHGT in 6.5. Hopefully it will be delivered soon. It will be chambered for 6.5 PRC and is fast twist as I'll be shooting solids. I need to get off my butt and have Mile High order me a 30 cal LHGT as I want one chambered for 300 PRC.

 

[LastShot300]

The idea that I see people mention, where the GT Barrel adds more impressions on the bullet is flat out WRONG. You are not laying across the bullet anymore, in fact, it is better for the bullet because you are not overspinning it from the start. Hornady has shown no issue with Pressure. (Hornady has been testing GT Barrels since I started crowing about them, they won't tell me the results, but they smile) Guys want to over spin the bullets for "TRANSONIC STABILITY" but at the same time, they want to push the bullet as fast as possible. This does not work, dont' believe me, why do you think the 300NM is suddenly not working out for the Army. The rest of the free world knows how to push a heavy 30 Cal, apparently, the Army missed the memo or spoke to the wrong guy. His 20" 300NM over spun is not the same as their 26" 300NM pushed 200fps faster. That moves the lead underneath, throws the bullet out of balance and causes accuracy issues as well as inconsistencies in BC and performance. (Sound Familiar)

I like em,

Great explanation of how things are really working out in the real world, but made me wonder, how come the .300NM is bashed out of accuracy and the PRC is not? This is all about the projectiles, not the cartridges themselves. I know TH walked down the Army to go short-barreled but that's just a bad advice not science. My question is how in hell can Hornady make it better? Internal ballistics is the same for everyone.

 

[AIAW]

Shortly after buying an AX MC last summer, I had Mile High order me a LHGT in 6.5. Hopefully it will be delivered soon. It will be chambered for 6.5 PRC and is fast twist as I'll be shooting solids. I need to get off my butt and have Mile High order me a 30 cal LHGT as I want one chambered for 300 PRC.

Cool. Fire up a thread when you get it (or even in this one). Interested in the charge differences people will report with the gain-twist vs standard twist, particularly 300 PRC.

 

[AIAW]

Great explanation of how things are really working out in the real world, but made me wonder, how come the .300NM is bashed out of accuracy and the PRC is not? This is all about the projectiles, not the cartridges themselves. I know TH walked down the Army to go short-barreled but that's just a bad advice not science. My question is how in hell can Hornady make it better? Internal ballistics is the same for everyone.

That's a good question. No need to elaborate how that works. Probably involves strippers, cigars and deals during a Louis XIII drinking spree.

I bitch about the .260 REM vs 6.5 CM marketing wank all the time.

 

[LastShot300]

That's a good question. No need to elaborate how that works. Probably involves strippers, cigars and deals during a Louis XIII drinking spree.

I bitch about the .260 REM vs 6.5 CM marketing wank all the time.

 

[Crews]

If I'm understanding correctly, there might be some benefit to the guy who only shoots factory ammo too right? Payoff is a little more consistency across a variety of projectiles.... does that also translate over to a potentially less velocity variation?

 

[Derek200]

I know infinity (SVI) uses gain twist in pistol barrels. Would left hand twist benefit the pistol sports as far as recoil management goes? Not sure I totally get what your saying the impact is to recoil from left hand twist...

 

[MarinePMI]

LH twist in pistols is more for managing recoil impulse and as a means to prevent stovepiping the brass in the ejection port. IIRC, that is why the .44 Automag had a LH twist. The torque during recoil with a rh Twist barrel would stove pipe the brass every time. But, when using a LH twist barrel, the brass would clear the ejection port every time.

Physics. Sometimes it's your friend. Other times it has you pulling your hair out...

 

[Derek200]

But how does it impact the recoil impulse?

 

[MarinePMI]

It affects the recoil impulse in that the torque (twist) of the pistol is changed from right to left. The pistol/barrel what's to move in response to something being forced to turn, in the barrel. "For every action, there is an equal and opposite reaction." So, when the bullet wants to spin (because of the rifling) to the right, the barrel wants to resist it, forcing an opposite torque (twist) of the pistol in the opposite direction (to the right), bringing the ejection port down and left (which causes the stove pipe). With a LH twist, the torque is moving the ejection port left and up, allowing the brass to clear the port more easily (I may be getting the directions backwards though, I'm still only on my second cup of coffee this morning). Now that I think about it, I'm pretty sure I have the directions backwards...but I think it still conveys the gist of what I'm talking about.

Clear as mud?

 

[Derek200]

Yup

 

[Precisiondada]

Ordered a left-twist Bartlein from Altus (formerly Core) based on this thread. Looking forward to putting it through it’s paces