rifling direction...

milktree

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How much does rifling direction *really* matter?

I bought a barrel blank from green mountain rifle barrels for an AR-9 project, profiled it, and wasn't really happy with its performance.

Then I realized that there is a "muzzle" end and a "breech" end to the blank, and I *probably* got it backwards. (It's been a while, so this is from foggy memory)

My understanding was that you draw the button from the breech to the muzzle, because the *entrance* hole *at the breech, has more distortion than the exit hole. Therefore, if you put the chamber at the "bad" end, you erase all the distortion. But if you cut off a sufficient amount from the "bad" end, it doesn't really matter which way the barrel goes.

e.g.: if you start with a 17.5" barrel, and cut 1" off the "bad" end, it doesn't matter which way you use the barrel.


However, when talking to a rep at Green Mountain today, she said the actual direction the button was pulled through the barrel always matters, no matter how much you cut off.

Which is to say, the only way I'm going to get the best performance out of this barrel is to go back in time and swap ends.

Is that actually true? Does which way the button was pulled matter if you erase the entry end?
 
Are you asking if it's ok of the projectile spins counter clockwise coming out of the barrel compared to clockwise on every other barrel?
 
How much does rifling direction *really* matter?

I bought a barrel blank from green mountain rifle barrels for an AR-9 project, profiled it, and wasn't really happy with its performance.

Then I realized that there is a "muzzle" end and a "breech" end to the blank, and I *probably* got it backwards. (It's been a while, so this is from foggy memory)

My understanding was that you draw the button from the breech to the muzzle, because the *entrance* hole *at the breech, has more distortion than the exit hole. Therefore, if you put the chamber at the "bad" end, you erase all the distortion. But if you cut off a sufficient amount from the "bad" end, it doesn't really matter which way the barrel goes.

e.g.: if you start with a 17.5" barrel, and cut 1" off the "bad" end, it doesn't matter which way you use the barrel.


However, when talking to a rep at Green Mountain today, she said the actual direction the button was pulled through the barrel always matters, no matter how much you cut off.

Which is to say, the only way I'm going to get the best performance out of this barrel is to go back in time and swap ends.

Is that actually true? Does which way the button was pulled matter if you erase the entry end?
Rifling can be left or right spin, doesn't matter to performance.
 
How much does rifling direction *really* matter?

I bought a barrel blank from green mountain rifle barrels for an AR-9 project, profiled it, and wasn't really happy with its performance.

Then I realized that there is a "muzzle" end and a "breech" end to the blank, and I *probably* got it backwards. (It's been a while, so this is from foggy memory)

My understanding was that you draw the button from the breech to the muzzle, because the *entrance* hole *at the breech, has more distortion than the exit hole. Therefore, if you put the chamber at the "bad" end, you erase all the distortion. But if you cut off a sufficient amount from the "bad" end, it doesn't really matter which way the barrel goes.

e.g.: if you start with a 17.5" barrel, and cut 1" off the "bad" end, it doesn't matter which way you use the barrel.


However, when talking to a rep at Green Mountain today, she said the actual direction the button was pulled through the barrel always matters, no matter how much you cut off.

Which is to say, the only way I'm going to get the best performance out of this barrel is to go back in time and swap ends.

Is that actually true? Does which way the button was pulled matter if you erase the entry end?

Did some poking around and haven't found a good reference. It's an interesting question. Presuming the question regards button pull/push direction relative to the breach-end. I did find a similar discussion on this here:

 
Some people have claimed twist direction matters because of the Coriolis Force, but I've never seen any plausible tests that confirm it.

But as someone said, if you rifle for RH twist, it's still RH no matter which direction the barrel points.
 
Did some poking around and haven't found a good reference. It's an interesting question. Presuming the question regards button pull/push direction relative to the breach-end. I did find a similar discussion on this here:


Well, that's extra confusing then. Green Mountain said the *muzzle* end was marked, but everyone on that page says the *chamber* end is marked.

1) Green Mountain rep told me the wrong thing
2) Green Mountain does it differently.
 
Are you asking if it's ok of the projectile spins counter clockwise coming out of the barrel compared to clockwise on every other barrel?

No. Left vs. right hand twist is irrelevant. The question is about which end of the blank should you cut the chamber in, and does it matter if you get it wrong if you cut off XXX from the muzzle.

Probably not since flipping a barrel won't change the rifling direction.

Just like any other threads or helix!

Rifling can be left or right spin, doesn't matter to performance.

The Internet agrees with you!

It especially doesn't matter on the context of 9mm. :)
 
Well, that's extra confusing then. Green Mountain said the *muzzle* end was marked, but everyone on that page says the *chamber* end is marked.

1) Green Mountain rep told me the wrong thing
2) Green Mountain does it differently.

I think I've primarily seen the chamber ends marked on finished barrels. I don't recall markings on the muzzle end before. Muzzle end seems odd since any finish profile and threading for a brake would limit the marking area. Though, if a blank that has been button rifled is truly bidirectional, it wouldn't matter of course.

I do have to wonder though, even if there is a directional pattern / grain / etc caused by pulling the button, what would the consequence really be? Would it be sufficient to cause some sort of accuracy issue? Or is it mostly a fouling thing?
 
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No. Left vs. right hand twist is irrelevant. The question is about which end of the blank should you cut the chamber in, and does it matter if you get it wrong if you cut off XXX from the muzzle.



Just like any other threads or helix!



The Internet agrees with you!

It especially doesn't matter on the context of 9mm. :)
The only reason I know it doesn’t matter is that some European rifle manufacturers use left hand rifling. Why they do it different I have no idea. I suppose it could be tradition, maybe it’s based on tooling, not sure.
 
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I think I've primarily seen the chamber ends marked on finished barrels. I don't recall markings on the muzzle end before. Muzzle end seems odd since any finish profile and threading for a brake would limit the marking area. Though, if a blank that has been button rifled is truly bidirectional, it wouldn't matter of course.

I do have to wonder though, even if there is a directional pattern / grain / etc caused by pulling the button, what would the consequence really be? Would it be sufficient to cause some sort of accuracy issue? Or is it mostly a fouling thing?

In my case, the blank is literally a blank. It's 1.25" in diameter, 17.5" long. No profiling at all: straight cylinder:


I'm not sure that grain direction is important for my application (9mm AR based PCC), but I can imagine it makes a difference to bench rest shooters.

My concern is if the process of pulling the button through can distort one end enough to make accuracy go to hell. I'm seeing 6" groups at 50 yards. That seems... pretty terrible. Yea, it's only a 9mm, so I shouldn't expect sub MOA, but my .38 lever gun does a lot better, and my 9mm CX-4 does a lot better, so I know it's possible.

If I can simply ("simply", har) cut off the distorted bit from the muzzle and re-crown, that's the easiest answer.
 
My concern is if the process of pulling the button through can distort one end enough to make accuracy go to hell. I'm seeing 6" groups at 50 yards.

Ok, I see. And, yeah, don't know. Not to confuse this more but could there have been a heat-treat problem (or for that matter no heat treat)?
 
Twist does impart some counter-torque. In a rifle, this will affect POI to some small degree because it affects the recoil, but it probably varies more between RH/LH shooters than between RH/LH twist.
 
In my case, the blank is literally a blank. It's 1.25" in diameter, 17.5" long. No profiling at all: straight cylinder:


I'm not sure that grain direction is important for my application (9mm AR based PCC), but I can imagine it makes a difference to bench rest shooters.

My concern is if the process of pulling the button through can distort one end enough to make accuracy go to hell. I'm seeing 6" groups at 50 yards. That seems... pretty terrible. Yea, it's only a 9mm, so I shouldn't expect sub MOA, but my .38 lever gun does a lot better, and my 9mm CX-4 does a lot better, so I know it's possible.

If I can simply ("simply", har) cut off the distorted bit from the muzzle and re-crown, that's the easiest answer.

From: Rifling Machine and Methods, Clifford LaBounty 2011.

1654130634550.png

Don't know if this applies since you've noted your barrel as a bull barrel with no profiling ... but interesting never-the-less.

This reference does note some various aspects, such as lapping, where they point out the specific direction, e.g. rod insertion from the chamber end. But haven't found something specific related to entry distortion as of yet.
 
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Maybe the barrel just sucks. Does Green Mountain guarantee any kind of accuracy?

I've had the barrel long enough that there's no way I could, in good conscience, blame them. I think I bought it in '16, (or at least back ordered it in '16), didn't get around to getting it in a lathe until '20, and now it's '22 (lame)

Also, when I bought it, it looked like this:

IMG_0458.JPG

And now it looks (pretty much) like this:

IMG_0583.JPG

So, they'd be totally reasonable to say, "dude, you erased half the steel, how can you say it's our fault?"


And and... it's only $42, and there are lots of great reviews. Green Mountain has a pretty good reputation I think.
 
From: Rifling Machine and Methods, Clifford LaBounty 2011.

View attachment 622321

Don't know if this applies since you've noted your barrel as a bull barrel with no profiling ... but interesting never-the-less.

This reference does note some various aspects, such as lapping, where they point out the specific direction, e.g. rod insertion from the chamber end. But haven't found something specific related to entry distortion as of yet.

Huh.. that is interesting. It makes total sense (now that someone else has put it in print. :)

I think it's not directly applicable to my problem though. It doesn't specifically say on the product page that they stress relieve that particular blank, but there's a general "how we do it" page:


that says,

Green Mountain Rifle Barrel said:
... we subject each barrel to a stress relieving procedure to ensure uniform steel cell structure and barrel straightness.

That does bring up another question: Do I need to do a stress relieving process now that I've profiled the barrel?

I *think* that's not necessary, but I can't tell you specifically why I think that.
 
The Coriolis stuff has potential
(especially since everyone on NES thinks their rifle is a railway gun).

But this thread won't really deliver
until someone talks about button-rifling's effects
upon the steel's "pores".

Rifling can be left or right spin, doesn't matter to performance.
Even if you are in the southern hemisphere?
Word.
 
I've had the barrel long enough that there's no way I could, in good conscience, blame them. I think I bought it in '16, (or at least back ordered it in '16), didn't get around to getting it in a lathe until '20, and now it's '22 (lame)

Also, when I bought it, it looked like this:

View attachment 622384

And now it looks (pretty much) like this:

View attachment 622387

So, they'd be totally reasonable to say, "dude, you erased half the steel, how can you say it's our fault?"


And and... it's only $42, and there are lots of great reviews. Green Mountain has a pretty good reputation I think.

Well that's probably not worth the hassle even if they do.


I know a machinist who works on guns for one of the top highpower rifle shooters in the U.S. ,and he uses Green Mountain barrels on his personal custom rifles. He once told me he uses Green Mountain barrels because he's always used Green Mountain barrels. This conversation came when I asked him who made the best barrels.
 
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