RIFLING questions

[M-61]

Any experimenting with depth of rifling on BR rifles? I've owned a few Marlin's with their 'micro-goove' rifling and for what they were (long ways from BR) their accuracy was just fine. Wonder what the depth effects?
Any experimenting with gain twist? Seems most everything from 20mm and up is a gain twist. You can get as strange as Holland and Hollands Paradox but my question is what sets any standard for the depth of the rifling?
How shallow can you get and how does it do? Is it less friction? Is it easier to clean?

 

[Alex Wheeler]

I have with bore size and groove depth as well as gain twists. Bore size doesnt make a big difference. Groove size does. Gain twist is a hard thing to quantify, but personally I will always put some gain in if its an option. I do believe it helps.

 

[jackieschmidt]

Gain twist barrels have a pretty good following since Bartlien figured out the process with their CNC cut rifling process of generating what ever gain needed.

The old method of cut rifling using the old Sine Bar machines required actually tweaking the guide that produced the twist rate in the tool. Barlien‘s method, (in my opinion), is superior. in producing consistent results.

As far as rifling goes, In Short Range BENCHREST, I have seen and tried just about every configuration imaginable through the 30 years I have been involved. Maybe in some Disciplines it makes a difference, but I have found that a regular .237 bore 4 groove barrel is hard to beat, with the emphasis in keeping the groove diameter exact.

One problem with barrels is a good shooter in what ever Discipline he is participating in will acquire a really exceptional barrel in a particular land and groove configuration, shoot some phenomenal scores, and suddenly everybody wants one.

The truth is the barrel would have been exceptional regardless of the land and groove configuration.

 

[357Mag]

Any experimenting with depth of rifling on BR rifles? I've owned a few Marlin's with their 'micro-goove' rifling and for what they were (long ways from BR) their accuracy was just fine. Wonder what the depth effects?
Any experimenting with gain twist? Seems most everything from 20mm and up is a gain twist. You can get as strange as Holland and Hollands Paradox but my question is what sets any standard for the depth of the rifling?
How shallow can you get and how does it do? Is it less friction? Is it easier to clean?

M-61 -

Howdy !

Here's one of my " experimenting with depth of rifling on BR rifles "....

I've have / had Marlin lever guns w/ " micro-groove " rifling. Some of those Marlins came w/ " Ballard " style
rifling, which features ( what I believe are ) deeper " grooves ".

My M-336 XLR .35 Remington came w/ 12-groove " Ballard " rifling. The rifle is very accurate, when I do my part. Misreading the windflag for the last 2 shots ( of the pictured 5-shot 100yd group ) is not " doing
my part ".

IMHO - Deeper grooves can work just fine, when the bullet obturates to fit the rifling / bore.
In this " experiment ", my XLR out-shot my older -60's era " micro-groove " M-336 .35 Remington.


With regards,
357Mag

 

[Forum Boss]

My PacNor 3-groove barrel has wide grooves and lands, and the grooves appear shallow relative to the height of the lands. In other words there isn't that much diametrical difference between lands and grooves, at least as seen by the eye through the borescope. This configuration has delivered significantly more velocity with a 6BR cartridge than is typical. With the same charge weight and bullet, the 3-groove runs about about 20-25 fps faster than my 6-groove cut-rifled barrel that is 1" longer. Every barrel is different of course. But I discussed this with John Krieger and he believed that a 3-groove might well be faster than other configurations.

 

[rwj]

You may find some interesting findings here… https://discover.dtic.mil/results/?q=Rifling#gsc.tab=0&gsc.q=Rifling&gsc.page=1

 

[PigButtons]

If i might ask a question here, it seems like the right place without starting a new thread.

Is there some formula for determining the twist rate from the intended bullet? Something like, bearing length divided by half the diameter, times some constant , gives twist rate in inches.

 

[gunsandgunsmithing]

If i might ask a question here, it seems like the right place without starting a new thread.

Is there some formula for determining the twist rate from the intended bullet? Something like, bearing length divided by half the diameter, times some constant , gives twist rate in inches.

Berger has a twist rate calculator on their site. Maybe this is what you're referring to. Bearing surface has little or maybe nothing to do with twist rate except for its role in overall bullet length, imho.

Twist Rate Stability Calculator

Our newly updated Twist Rate Stability Calculator not only tells you what your SG is, but it also lets you know if you are reaching your optimized BC.

bergerbullets.com

 

[M-61]

I also have a three groove in 30BR. Also 2 five groove. I don’t have a chrono but both are extremely accurate. My thought was for what ever reason the 3 groove would be better. Actually there is little difference at least any that I could determine.
I was told by a former member my thought process was wrong. Anything wrong in the 3 groove represents 1/3 of all the rifling. Whereas in a 5 or more it represented a smaller percentage . Now what he meant by ‘wrong’ I don’t know.
Does anyone ask a rifler what depth they would like there rifling to be?
Is button rifling one pass of the button and that’s it?
To me the shallowest rifling that will impart spin on the projectile should be good. Is there an accepted depth that has been proven to be the best?
I know nothing about this at all and I’ve never known a Rifler to ask. I’ve just accepted they know. Wondering about ease of cleaning, friction, accuracy, longevity.
The barrels I have on my br rifles are fine and these questions are to try and further my knowledge.
Tanks for all the replies.
Really would liked to have asked Gerald Bull who always was always thinking outside the box!

 

[Charwell]

If i might ask a question here, it seems like the right place without starting a new thread.

Is there some formula for determining the twist rate from the intended bullet? Something like, bearing length divided by half the diameter, times some constant , gives twist rate in inches.

the greenhill rifling formula

 

[jackieschmidt]

One of the best authorities on twist and bullet configuration is Randy Robinett of BIB bullets.

 

[CharlieNC]

You may find some interesting findings here… https://discover.dtic.mil/results/?q=Rifling#gsc.tab=0&gsc.q=Rifling&gsc.page=1

WOW there are a tremendous number of reports here! It will take quite a while just to survey the content. I knew the DOD had all of this somewhere!

 

[rwj]

WOW there are a tremendous number of reports here! It will take quite a while just to survey the content. I knew the DOD had all of this somewhere!

Yes, but what you see there is only the information that has been declassified…

 

[PigButtons]

the greenhill rifling formula

This is exactly what I was looking for. Great help, thanks.

 

[PigButtons]

I also have a three groove in 30BR. Also 2 five groove. I don’t have a chrono but both are extremely accurate. My thought was for what ever reason the 3 groove would be better. Actually there is little difference at least any that I could determine.
I was told by a former member my thought process was wrong. Anything wrong in the 3 groove represents 1/3 of all the rifling. Whereas in a 5 or more it represented a smaller percentage . Now what he meant by ‘wrong’ I don’t know.
Does anyone ask a rifler what depth they would like there rifling to be?
Is button rifling one pass of the button and that’s it?
To me the shallowest rifling that will impart spin on the projectile should be good. Is there an accepted depth that has been proven to be the best?
I know nothing about this at all and I’ve never known a Rifler to ask. I’ve just accepted they know. Wondering about ease of cleaning, friction, accuracy, longevity.
The barrels I have on my br rifles are fine and these questions are to try and further my knowledge.
Tanks for all the replies.
Really would liked to have asked Gerald Bull who always was always thinking outside the box!

Maybe a slight thread drift, but just something to think about. FX air rifle company came up with a novel barrel design called the SMOOTH TWIST. It was smooth bore for the first four-fifths of the barrel, then had a progressive twist. They shot great and had just one drawback, they had to be cleaned about every 20 shots to maintain accuracy. They have a different one now the details of which I am not familiar.

 

[Fuj]

Maybe a slight thread drift, but just something to think about. FX air rifle company came up with a novel barrel design called the SMOOTH TWIST. It was smooth bore for the first four-fifths of the barrel, then had a progressive twist. They shot great and had just one drawback, they had to be cleaned about every 20 shots to maintain accuracy. They have a different one now the details of which I am not familiar.

An extreme bore rider ??

 

[PigButtons]

An extreme bore rider ??

I had to look that up. But yes, that would be a fitting description.

 

[wkdickinson]

the greenhill rifling formula

Why is the Miller twist rule better than the Greenhill rifling formula?

The Miller twist rule is better than the Greenhill rifling formula because it is desinged to accurately measure modern long-range bullets.

bergerbullets.com

 

[divingin]

My PacNor 3-groove barrel has wide grooves and lands, and the grooves appear shallow relative to the height of the lands. In other words there isn't that much diametrical difference between lands and grooves, at least as seen by the eye through the borescope. This configuration has delivered significantly more velocity with a 6BR cartridge than is typical. With the same charge weight and bullet, the 3-groove runs about about 20-25 fps faster than my 6-groove cut-rifled barrel that is 1" longer. Every barrel is different of course. But I discussed this with John Krieger and he believed that a 3-groove might well be faster than other configurations.

Does this also imply the need to load down a bit to hit the same node as a more "standard" rifling pattern? Or is it lost in the noise?

 

[Forum Boss]

Does this also imply the need to load down a bit to hit the same node as a more "standard" rifling pattern? Or is it lost in the noise?

Actually it meant I could shoot at a FASTER velocity which had better ballistics. But this rifle basically shot 105s into a group as small as I could hold at every velocity from 2880 up to 2920. The 2920 speed shot great but was tough on the brass, so I settled on about 2910.

Nodes are real, but I've had 3 barrels that just drilled everything (over a 30 fps span) into very small groups as long as I had the bullets about .006-.008 in the lands. YMMV. I've seen the same thing with a friend's 30 BR.