Barrel rifling

BoltGunner054

BoltGunner054

Private
Minuteman
Jul 17, 2023
43
25
Pennsylvania
#1
Ordered a barrel and was asked 5 or 6 groove rifling. Going to sound stupid here but what is everyone shooting? Does it make that much of a difference? I’m far from a professional. Initial research claims bullet/jacket deformation with 6 groove. I watched the bartlein video and he says 5. Everything seems conflicting so looking for info from folks who use and know this stuff. Barrel is a 26” heavy varmint 1-8 twist chambered in 6.5 creedmoor. Thanks in advance.
 
#5
moaorbust said:
It doesn’t matter. I used to shoot 4 groove and now 5 groove. I am the weakest link regardless of groove. Your twist matters far more as it needs to match the bullet weight to stabilize the spin. That said, anything Bryan Litz says is gospel.
Click to expand...

I’ve shot dozens of 4-6 grooves and don’t see any difference in barrel performance or life. I find a good barrel is a good barrel.
 
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#6
oldrifleman said:
Frank has said in a couple of threads that 5 groove barrels seem to disturb bullet jackets less.
Click to expand...

We've worked with a couple of barrel MFG's and found the same trend with both 5R and 5-groove traditional rifling.

At the end of the day 4-groove seems to be a traditional carryover from forever ago. Most everything that was made around the time countries adopted smokeless powder was a 4-groove barrel. There are some exceptions in the mid/late 1800's black powder era stuff, but the Krag, Mausers, M1903, Swiss straight pulls (after the 1889 BP rifle), Mosin Nagants, etc.. Pretty much every popular rifle except the Lee Enfield (5G, LH) was 4 groove. There were some war-time simplifications in WWII to make 2-groove barrels but those are exceptions to the rule.

I don't know where 6-groove made it's introduction but now it's often used in SAAMI cartridge introductions-- and as far as I can tell that's purely because the groundwork has already been done and it's an easy cut/paste option.

All of that being said, it's usually not make or break any way. However, when given the choice (unless it costs dramatically more for some obscene reason) I opt for 5 groove-- Ideally 5R. 4G and 6G seem to have a higher propensity to cause bullet failures if you're pushing the limits but tight spots, burrs, and other manufacturing defects can cause the same thing regardless of rifling style. 4G with sharp corners also seems to do a bit better on the whole with short bearing surface match/varmint bullets (think short range BR)... But again for what we're doing I haven't ever seen any compelling evidence that it's meaningfully different between 4G, 5G, 5R, or 6G. Barrel-to-barrel variation still seems to trump rifling type/profile.
 
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#7
Ledzep said:
We've worked with a couple of barrel MFG's and found the same trend with both 5R and 5-groove traditional rifling.

At the end of the day 4-groove seems to be a traditional carryover from forever ago. Most everything that was made around the time countries adopted smokeless powder was a 4-groove barrel. There are some exceptions in the mid/late 1800's black powder era stuff, but the Krag, Mausers, M1903, Swiss straight pulls (after the 1889 BP rifle), Mosin Nagants, etc.. Pretty much every popular rifle except the Lee Enfield (5G, LH) was 4 groove. There were some war-time simplifications in WWII to make 2-groove barrels but those are exceptions to the rule.

I don't know where 6-groove made it's introduction but now it's often used in SAAMI cartridge introductions-- and as far as I can tell that's purely because the groundwork has already been done and it's an easy cut/paste option.

All of that being said, it's usually not make or break any way. However, when given the choice (unless it costs dramatically more for some obscene reason) I opt for 5 groove-- Ideally 5R. 4G and 6G seem to have a higher propensity to cause bullet failures if you're pushing the limits but tight spots, burrs, and other manufacturing defects can cause the same thing regardless of rifling style. 4G with sharp corners also seems to do a bit better on the whole with short bearing surface match/varmint bullets (think short range BR)... But again for what we're doing I haven't ever seen any compelling evidence that it's meaningfully different between 4G, 5G, 5R, or 6G. Barrel-to-barrel variation still seems to trump rifling type/profile.
Click to expand...
Yeah all of this would become more pronounced if you are pushing velocities into the “fun”zone ( ex: 6 cm above 3200🤣).
 
#15
moaorbust said:
It doesn’t matter. I used to shoot 4 groove and now 5 groove. I am the weakest link regardless of groove. Your twist matters far more as it needs to match the bullet weight to stabilize the spin. That said, anything Bryan Litz says is gospel.
Click to expand...
BS it doesn't matter! Years ago... I did always say that the number of grooves didn't mean squat in terms of barrel life or accuracy.

For the most part!

I did always say if shooting short jacket 6mm bullets like bullets 85gr or less you want conventional rifling. 4 groove, 5 groove or 6 groove etc...especially with 6PPC type bench guns. They don't like the 5R rifling. Best you can typically get out of them is upper .2xx's to low .3xx's. The short range bench guys if your shooting in the upper .2xx's your not going to be competitive but the longer 6mm bullets... 5R all the way.

Now fast forward to several years ago and especially Aug. 2022. Testing was done and unknown to me we made all the test barrels. 7 of them had saami spec. 6 groove rifling and 5 had our 5R rifling. High pressure and high velocity.... the 5r rifling helped maintain consistent bc numbers on the bullets. The 6 groove rifling... was putting burrs on the side of the jacket of the bullets. the burr was as big as a 1/32" and effected the bc of the bullet by as much as 5%. The further down range the greater this 5% even though it doesn't sound like much will effect accuracy.

About 7 years ago Hornady and the Army ran into the same thing testing 5R and 4 groove barrels but didn't know why. That testing was done at 1k and 1200 yards.

Seeing the pictures of 320 bullets fired thru the 6 groove and 5R barrels now confirmed what Hornady and Army seen.
 
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#19
I have been going to 5 R the last several yrs. I get a bit higher velocity, and no bullet blow up in mid flight.
Even the 58 gr Vmax shoots good groups in the 6 Dasher at 4100 fps, with 7.5 twist barrel purchased for the 105 to 115 match bullets. The 110 SMK at 3085 is an excellent LR speed load, or drop down to 2975 to 3020 area with Berger 108s for super accuracy.
Two newer 308s are 9 and 8 twist 5 R for long bullets, the 8 twist is on a long action, for 200gr SMK 2860 fps to 230 gr Atips bullets, at 2620 fps, or 225 ELDM at 2675 fps.
The 5 R barrels are my preferred barrel rifling, for most of the shooting I do, if given a choice.
 
#20
Frank Green said:
Not even that fast.... I'll say starting at 3k.

Pressure though is also an issue even if you're not hitting that higher velocity.
Click to expand...
I’m right around 2650-2700 currently. With the new barrel 4” longer I expect to be in the previous said range. Currently I notice no pressure signs at all, everything seems great. So when 5R rifling isn’t an option you would recommend 5 over 6 from the sounds of it. Also is there any possibility you could link some literature to the tests that you had mentioned? It would be really interesting to read them. Thank you for your input. It is appreciated.
 
#21
I would be interested to know if it is the shape of the 5R rifling completely.
If 4 groove or 6 groove was made with the same shape lands, would it also perform the same.

Not even the "same" shape. Just more rounded off edges.

Since "R" is taken, could probably make millions patenting 4T and 6T rifling... T stands for "Tapered" lol
 
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#22
Frank Green said:
the burr was as big as a 1/32" and effected the bc of the bullet by as much as 5%. The further down range the greater this 5% even though it doesn't sound like much will effect accuracy.
Click to expand...
I'm surprised it's not several times that, a burr that size with a boolit spinning maybe 250,000 rpm I'd have thought it would have had more impact.
 
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#23
TheOE800 said:
I think last time this came up @AccuSol-ERN said that even-number groove barrels were easier to chamber, something about the pilot? Odd-number barrels require paying more attention or something.
Click to expand...
That is my observation from my machining setup. That is why I prefer quality 4 groove blanks. Others with different setups may have a different experience. A lot of builders just ream to final headspace and don't even check......at best they might scope it and look for obvious misalignment. It takes time and effort to clean and run an indicator back in to check critical chamber areas. Some builders, knowing the customer might use a borescope nowadays are spec'ing reamers with oversized freebore diameters (most SAAMI and match reamers are +.0005" bullet diameter) to "hide" visual signs of misalignment.......leaving rifling lands through the freebore while 180 degrees opposite is cut clean.

Does this effect accuracy?........maybe maybe not.......Can rifles still meet accuracy guarantee with misalignment?.....maybe maybe not. I know that misaligned chambers/freebores are hell on bullet jackets (especially Hornady) and can lead to mid air puffs.

The best we can do is get as close as possible while knowing there is tolerance stacking (although small) can add up. I am currently at my work bench trying to deal with a problem.......old Hornady 140ELDM mic out at .2641 and new factory ammo mic out at .2646-.2647.......customer experiences sticky close/extraction on live ammo.......SAAMI reamer specs .2645 and mics .2646ish. Going to set it back up in the lathe and run my custom throater .2652 in and make a skim cut without bumping length.

Meanwhile old Hornady ammo and other ammo using non-Hornady bullets work just fine, Bergers, Sierra, and old Hornady mic out between .2640-.2643........Gotta love Hornady's consistency!!!

Ern
 
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#24
BoltGunner054 said:
I’m right around 2650-2700 currently. With the new barrel 4” longer I expect to be in the previous said range. Currently I notice no pressure signs at all, everything seems great. So when 5R rifling isn’t an option you would recommend 5 over 6 from the sounds of it. Also is there any possibility you could link some literature to the tests that you had mentioned? It would be really interesting to read them. Thank you for your input. It is appreciated.
Click to expand...
I'd take a conventional 5 groove over a 4 or 6.

I don't know if Hornady has any data or not... (did they record it). They where doing doppler radar testing that day. Army did the same thing but was testing like 26 different 6.5mm bullets out to 1200 yards. It's been about 7 years so I don't even know who to ask if they saved any of the data. It was relayed over the phone to me.

The testing done two years ago... I've seen the data on the lap top. The test was run by a bullet maker for a gun manufacturer. I know who is in charge of the data at the manuf. and I've put in 3 requests to have it released to me but no response. The same manufacturer right now is testing different groove configurations, as well as different bore and groove sizes. We made them like 25 different test barrels. In a different caliber we made them some 338 barrels with really wide grooves with 4 groove rifling. It was almost at the limit of our existing tooling.
 
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#26
Wannashootit said:
I'm surprised it's not several times that, a burr that size with a boolit spinning maybe 250,000 rpm I'd have thought it would have had more impact.
Click to expand...
Bullets where spinning at 308k and change...

The only thing not factored in... and would need more extensive testing is as the barrel wears the throat is going to get rougher and in turn beat the bullet up even more.

It would be interesting to see what happens to the bullets when the barrels are new... then at 2k rounds and then at 4k rounds. That's a lot of shooting and a lot of $$$$$.
 
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#28
Frank Green said:
I'd take a conventional 5 groove over a 4 or 6.

I don't know if Hornady has any data or not... (did they record it). They where doing doppler radar testing that day. Army did the same thing but was testing like 26 different 6.5mm bullets out to 1200 yards. It's been about 7 years so I don't even know who to ask if they saved any of the data. It was relayed over the phone to me.

The testing done two years ago... I've seen the data on the lap top. The test was run by a bullet maker for a gun manufacturer. I know who is in charge of the data at the manuf. and I've put in 3 requests to have it released to me but no response. The same manufacturer right now is testing different groove configurations, as well as different bore and groove sizes. We made them like 25 different test barrels. In a different caliber we made them some 338 barrels with really wide grooves with 4 groove rifling. It was almost at the limit of our existing tooling.
Click to expand...
Thank you for a very knowledgeable, respectful, and informative response. I have no clue who you are but you seem like you’re a wealth of information so thank you for that.
 
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#32
Wow. Wasn’t aware a genuine thank you to somehow to truly doesn’t owe any info or explanation to anyone would ignite so much laughter. I guess I’m now a comedian. Sorry newer to the forum and literally yes a google search goes to reusable cups and stainless tumblers so that was a dead end.
 
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#33
BoltGunner054 said:
Wow. Wasn’t aware a genuine thank you to somehow to truly doesn’t owe any info or explanation to anyone would ignite so much laughter. I guess I’m now a comedian. Sorry newer to the forum and literally yes a google search goes to reusable cups and stainless tumblers so that was a dead end.
Click to expand...
It's a regular thing here. Don't worry about it.
 
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#34
oldrifleman said:
Frank Runs and I believe owns Bartlein Barrels. You are getting the scoop from THE MAN himself.
Click to expand...
I don’t own Bartlein. Tracy does. Myself, Andy and Tracy started Bartlein together.

Between Bartlein and Krieger when we worked there…. 26- 30 years now making barrels. Pretty much half my life. LOL!
 
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#35
Apologize for spreading false rumors. Yeah that is a fair bit of time making barrels. Sometimes we find the role that fits us and we enjoy. Now that you mention it I have been where I am for 2/3 of my life. Anyway glad to have you around!
 
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#36
oldrifleman said:
Apologize for spreading false rumors. Yeah that is a fair bit of time making barrels. Sometimes we find the role that fits us and we enjoy. Now that you mention it I have been where I am for 2/3 of my life. Anyway glad to have you around!
Click to expand...
No worries and no need to apologize!

I'll say the interesting thing about this stuff is we are always learning.... also the better technology for testing that is being done.... more things pop up.

Obermeyer always claimed the 5R rifling was more accurate but I don't think he had any real scientific data to back that up. Not sure. I really didn't believe in that but I did believe in the 5R rifling helped fight bullet failure.

Now in the last few years there is actual hard data that shows more of what is going on and how it effects the bullet. I think Boots (Obermeyer) was on to it but just couldn't explain it/had the hard data to back it up.
 
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#38
saddlerocker said:
I would be interested to know if it is the shape of the 5R rifling completely.
If 4 groove or 6 groove was made with the same shape lands, would it also perform the same.

Not even the "same" shape. Just more rounded off edges.

Since "R" is taken, could probably make millions patenting 4T and 6T rifling... T stands for "Tapered" lol
Click to expand...

Shilen makes a 4 groove " ratchet rifling" barrel,which has an interesting profile ,check it out.I have four ,that I'm very please with.
22Nosler
6 Creed
6.5 Creed
7 Why Mag

All shoot small,fast without over pressure signs , dont copper foul ( not comp. guns ,so my barrels never get hot) and clean easy
 
#39
Frank Green said:
Obermeyer always claimed the 5R rifling was more accurate but I don't think he had any real scientific data to back that up. Not sure. I really didn't believe in that but I did believe in the 5R rifling helped fight bullet failure.

Now in the last few years there is actual hard data that shows more of what is going on and how it effects the bullet. I think Boots (Obermeyer) was on to it but just couldn't explain it/had the hard data to back it up.
Click to expand...
Hey Frank.
In a previous thread somewhere here, I hinted at some of the correspondence with Boots but couldn't remember the details.
Today I stumbled into my old vendor file for him that was squirreled away in an inactive file cabinet.

Tons of faxes with pages full of his explanations, musings and best guesses. Even quite a few handwritten notes going deeper on things we discussed on the phone earlier. He would include those hand written notes with my barrel orders.

He contributed a lot to Jim Owens efforts in High Power competitions and is mentioned a lot in Jim's original website Jarheadtop.com. I think Jim got that site set up when the internet was brand new. I may be wrong but I think there used to be a forum connected to Jarheadtop.com and Boots was active on that.

Boots would regularly write articles and send them out under the name Boots Reload. Almost like a newsletter. Can't remember to many details but have that written down in this folder.

Looking at the volume of correspondence in this folder, I am astounded at just how passionate he was about barrels, ammo and accuracy. To be that damned busy and still be on fire about the topic so much that he would take time to fill multiple pages delving into minutia about a single side discussion was crazy. I appreciated him engaging me at the time but looking back now, it is humbling that he took so much time with a nobody like me simply because I was interested and wanted to learn.

It was also interesting to look back over the invoices he sent during the 90's and early 2000's.

An amazing fellow.
 
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#40
The above is truly awesome. I applaud all the guys using podcasts (or the internet in general) to document the knowledge and experience that will no doubt be lost otherwise.

To Frank's point, it is satisfying to read old books about theory and correlation that are now able to be proven and validated through advanced data collection.

I am the forever student......haha.

Frank - when are you writing a book? I would be fine with just a collection of theory/data/correspondence.....

Cheers

Ern
 
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#41
AccuSol-ERN said:
The above is truly awesome. I applaud all the guys using podcasts (or the internet in general) to document the knowledge and experience that will no doubt be lost otherwise.
Click to expand...
If I can find time and get my old scanner to work, I will try to scan some of this into PDFs.
If I get around to that, I will post here or start a new thread dedicated to Boots.

AccuSol-ERN said:
I am the forever student......haha.
Click to expand...
Likewise. I want to always keep an open mind, question what I'm doing and always invite Red Teaming.

AccuSol-ERN said:
Frank - when are you writing a book? I would be fine with just a collection of theory/data/correspondence.....
Click to expand...
I would buy one for sure. I would buy two if he included noods! LOL.
 
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#42
I'd be interested to hear @bohem has to say about this. I have a couple of his Osprey barrels (6 groove I believe but correct me if I'm wrong) and they shoot great.
 
#44
Maggot said:
I'd be interested to hear @bohem has to say about this. I have a couple of his Osprey barrels (6 groove I believe but correct me if I'm wrong) and they shoot great.
Click to expand...

We use a 6 groove with a trapezoidal cross section and a somewhat looser land:groove ratio than I usually saw in the various 5R's that we've cut over the years. I don't think, but I can't prove, that the MV and MV speed consistency we see in them comes from the 6 groove. I think it really has to do with the somewhat looser land:groove ratio we use and the honing of the bore provides exceptional consistency in circularity and cylindricity of the hole prior to rifling that the overall performance is much improved.

The 6 groove setup didn't show any accuracy performance difference with the 5R's that I was testing against with regular bullets. However I was seeing some benefits in pressure profiles, overall speed, and fouling of the bore with the jacketed bullets and monolithics when I was shooting them. I stayed with the 6 groove on the theory that if was potentially better with solids and showed no degredation with cup/core bullets so therefore it was overall a smart move. Additionally my mono designs use a bore rider design with a driving band to seal the bore and engage the rifling, the result being that it's similar in configuration to the short bearing surface light bullets than they are to something in similar overall length like a long range projectile.

I've never heard of the testing that @Frank Green is talking about but it sounds incredibly interesting, I would love to see the data if it is ever released to the public.

Even with knowledge that data exists to show that one groove pattern is better than the others I still suspect that the differences are probably far enough into the weeds that most of us, myself definitely included, should worry more about getting to the range than what groove pattern our custom rifle has in the bore. Especially now that I have two younger kids, a business, and a family I know I'm the weak link in the system these days.

@Frank Green thank you for taking the time to tell us about some of the testing, sounds like it was pretty cool to be involved with it.
 
Last edited:
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#45
Terry Cross said:
Hey Frank.
In a previous thread somewhere here, I hinted at some of the correspondence with Boots but couldn't remember the details.
Today I stumbled into my old vendor file for him that was squirreled away in an inactive file cabinet.

Tons of faxes with pages full of his explanations, musings and best guesses. Even quite a few handwritten notes going deeper on things we discussed on the phone earlier. He would include those hand written notes with my barrel orders.

He contributed a lot to Jim Owens efforts in High Power competitions and is mentioned a lot in Jim's original website Jarheadtop.com. I think Jim got that site set up when the internet was brand new. I may be wrong but I think there used to be a forum connected to Jarheadtop.com and Boots was active on that.

Boots would regularly write articles and send them out under the name Boots Reload. Almost like a newsletter. Can't remember to many details but have that written down in this folder.

Looking at the volume of correspondence in this folder, I am astounded at just how passionate he was about barrels, ammo and accuracy. To be that damned busy and still be on fire about the topic so much that he would take time to fill multiple pages delving into minutia about a single side discussion was crazy. I appreciated him engaging me at the time but looking back now, it is humbling that he took so much time with a nobody like me simply because I was interested and wanted to learn.

It was also interesting to look back over the invoices he sent during the 90's and early 2000's.

An amazing fellow.
Click to expand...
Boots was cool to talk to! If you got him started... don't hang up the phone!

Him and Jim were very tight! Jim ran RCLRC range back in the 80's and 90's. Boots made his barrels and did the install work etc... for Jim most of the time. A few guys convinced Jim to start teaching classes for hi power shooting to help new shooters coming into the sport. I'm happy to say I was in on the 2nd class he did and took a few more after that. You always learned/came away with some new knowledge. I'd say Jim was right in the regards it probably cut 3-5 years off of a new shooters learning curve. During the course of the classes Jim also got a gun builder or two (custom smiths) and go over builds etc... and then in another class usually Boots or John Krieger came in and talked about barrels.

Boots was as good of a barrel maker as he was a gunsmith (that's how it started for them... his family owned a gun store in Racine....and then he went to gunsmithing school and then shortly after that he got some equipment and started making barrels) as well as he was an excellent hi power shooter. Pulling his targets was pretty cool to say the least. Talk about a guy who could just pound the center of the target with iron sights let alone a scope. One of the matches I was at and if I recall correctly he won it as well... he laughed after the match and someone asked what was so funny? He said he just realized he grabbed the wrong ammo....he brought his culls/practice ammo to the match instead of his match ammo! Like I said... the guy could shoot also!

Later, Frank
 
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#46
There's a lot of posts in here that I might go back and read.
Talks to whomever is cutting the chamber and ask them what reamer they're using. if the lands don't sync up with the flutes on the reamer it can bounce and induce vibration. If he's running a 5 flute reamer, then a 5 groove would be ideal. If he's running an even number of flutes, then any even number of grooves will work, because the 180 degree flute will always be stabilized in cut also.
 
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#47
bohem said:
I've never heard of the testing that @Frank Green is talking about but it sounds incredibly interesting, I would love to see the data if it is ever released to the public.

Even with knowledge that data exists to show that one groove pattern is better than the others I still suspect that the differences are probably far enough into the weeds that most of us, myself definitely included, should worry more about getting to the range than what groove pattern our custom rifle has in the bore. Especially now that I have two younger kids, a business, and a family I know I'm the weak link in the system these days.

@Frank Green thank you for taking the time to tell us about some of the testing, sounds like it was pretty cool to be involved with it.
Click to expand...
Your welcome!

So here is the only picture I was given after several requests and it's a redacted photo... what I mean is... it's set up so the more you zoom in..... the blurrier it gets.

This is one of the bullets fired out of the conventional 6 groove rifling. What I'm trying to point to in the photo is a burr on this particular bullet. The shiny part is the burr and the cameras flash is reflecting off the burr.

1731679975083.png
 
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#48
bohem said:
should worry more about getting to the range
Click to expand...
^^^^ this says volumes if you guys are not paying attention.....

You gotta good gun that shoots very well... Get range time and shoot matches/practice with it. Once you finally realize you have a great gun... then when you make the wind calls and put the dope on your gun and that bullet goes where it's suppose to.... you become a better shooter and your learning more than you might realize... not to mention your confidence goes up as well.
 
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#49
Frank Green said:
Your welcome!

So here is the only picture I was given after several requests and it's a redacted photo... what I mean is... it's set up so the more you zoom in..... the blurrier it gets.

This is one of the bullets fired out of the conventional 6 groove rifling. What I'm trying to point to in the photo is a burr on this particular bullet. The shiny part is the burr and the cameras flash is reflecting off the burr.

View attachment 8546665
Click to expand...
Thanks! That's really interesting, it looks like there might be something there at 180 degrees opposite as well. I am going to have to slug some barrels and see if I can create a burr like that in a static test.
 
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#50
Tokay444 said:
There's a lot of posts in here that I might go back and read.
Talks to whomever is cutting the chamber and ask them what reamer they're using. if the lands don't sync up with the flutes on the reamer it can bounce and induce vibration. If he's running a 5 flute reamer, then a 5 groove would be ideal. If he's running an even number of flutes, then any even number of grooves will work, because the 180 degree flute will always be stabilized in cut also.
Click to expand...
Don't get too hung up on this. Most builders (myself included) may have preferences that work slightly better with our particular setups.....but by no means are we putting out substandard work otherwise. As pointed out here, there are many more influential variables that can be (and should be) chased instead.

Ern
 
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