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5R vs 4 Groove

N

nick338

Commander- of what I have no idea
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Feb 21, 2013
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Need to bring this up and hopefully not start a shit storm but I need to make the decision for a new build and I'm getting conflicting information. Have been told by several builders including one that will only use a 4 groove barrel for builds that the 4 groove makes for a more accurate rifle. 2 of them have stated that it's much easier to cut a chamber without "chatter" vs a 5R barrel which in turn provides better accuracy in the end.

That would be great if I had not heard specifically from Bartlein that in testing at ELR the bullets shot from the 4 groove vs the 5R exhibit "hop" when hitting transonic". I'm not sure how much this has an effect on accuracy if at all but I guess I don't want to take a chance shooting out to a mile when there are so many other factors involved.

So I'm hoping to hear from some guys here that can relate to either one of these claims so I can decide which is the better way to pursue this build.

Thanks
 
There’s some correlation that 4 grove barrels are more prone to seeing bullets have issues blowing up
I have two 4 grove barrels right now that I have had bullets from a certain popular bullet manufacturer blow up.
The bullets in the yellow boxes aren’t blowing up in those barrels though.
I have 2 new 4 grove barrels right now ready to go, I’ll just avoid the other bullets that have given me issues and happily shoot them.
 
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Steel head said:
There’s some correlation that 4 grove barrels are more prone to seeing bullets have issues blowing up
I have two 4 grove barrels right now that I have had bullets from a certain popular bullet manufacturer blow up.
The bullets in the yellow boxes aren’t blowing up in those barrels though.
I have 2 new 4 grove barrels right now ready to go, I’ll just avoid the other bullets that have given me issues and happily shoot them.
Click to expand...
Agreed. I’d stick to 5R
 
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Steel head said:
What is hop?
Click to expand...
Its kind of like bouncing
Will Ferrell Jump GIF - Find & Share on GIPHY
 
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Steel head said:
There’s some correlation that 4 grove barrels are more prone to seeing bullets have issues blowing up
I have two 4 grove barrels right now that I have had bullets from a certain popular bullet manufacturer blow up.
The bullets in the yellow boxes aren’t blowing up in those barrels though.
I have 2 new 4 grove barrels right now ready to go, I’ll just avoid the other bullets that have given me issues and happily shoot them.
Click to expand...

That's interesting as I have seen this exact issue with my 4 groove vs my bartlein 5r barrels.

I have found all of my bartleins to be the easiest to load for period. Way less fussy with bullet type and seating depth.

But I agree with @padom if your Smith can't chamber a 5r I would be getting someone else to chamber the battel.
 
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RTPERTHUIS said:
Bartlein 5R and Brux 4 groove - both will shoot 1,000 with the same accuracy. No issues with bullets "hopping" here.
Click to expand...

I specifically stated transonic so if your bullets are not transonic at 1k the point is irrevelant.
 
Steel head said:
What is hop?
Click to expand...

Maybe a rep from Bartlein can chime in here since that was where the info originated from but my guess is they believe the 4 groove rifling engraves the jacket differently than the 5R does and causes some disturbance in flight at transonic speeds that they are not seeing with 5R barrels.
 
Steel head said:
There’s some correlation that 4 grove barrels are more prone to seeing bullets have issues blowing up
I have two 4 grove barrels right now that I have had bullets from a certain popular bullet manufacturer blow up.
The bullets in the yellow boxes aren’t blowing up in those barrels though.
I have 2 new 4 grove barrels right now ready to go, I’ll just avoid the other bullets that have given me issues and happily shoot them.
Click to expand...

I don't believe the issue people are having with bullets blowing up in flight is a rifling issue, but more a Hornady issue. I can confirm several 5R barrels that have had ELD bullets blow up in flight.
 
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nick338 said:
I don't believe the issue people are having with bullets blowing up in flight is a rifling issue, but more a Hornady issue. I can confirm several 5R barrels that have had ELD bullets blow up in flight.
Click to expand...
My 6.5 PRC 5R does 147s
 
nick338 said:
I don't believe the issue people are having with bullets blowing up in flight is a rifling issue, but more a Hornady issue. I can confirm several 5R barrels that have had ELD bullets blow up in flight.
Click to expand...
My 4 grove 260 and 7mm blew up 147 and 180 and even some 190’s all at reasonable speeds.
I do think it is more a Hornandy issue than a rifling issue as well but some respectable People have said 5r are easier on bullets.
As for trans sonic I’ve found if your twist is decent it’s not generally a big deal.
 
I 2nd the 147 ELD blowing up in 5r
 
If a smith is saying it cant be done or wont shoot because you dont use his spec then decide if you trust the smith.

Sounds like someone has a stock of them to sell

To say you cant cut a straight chamber on a 5r is retarded.
2 groove 3 groove 4 groove 5 groove
Buttoned vs cut
Frozen vs not
And all the other stuff ....
A good smith will cut a good chamber.
Most of today's barrels from good makers are problem free and very accurate to the point you cant tell the difference.
 
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nick338 said:
Maybe a rep from Bartlein can chime in here since that was where the info originated from but my guess is they believe the 4 groove rifling engraves the jacket differently than the 5R does and causes some disturbance in flight at transonic speeds that they are not seeing with 5R barrels.
Click to expand...

You can ask several reputable smiths like Dave Tooley, George Gardner at GAP, Moon at Crescent Customs, Mark Gordon at SAC etc....

The whole chambering and chatter thing I don’t see it. We ourselves chamber in excess of a 1000 barrels a year and probably 60% of those are 5R style rifling and we don’t see any issues vs a 4 groove or 6 groove barrel.

I’ve maintained for several years now that the 5R style rifling does help fight bullet failure. Bullets can fail because the bullet can be a problem but with in saying that I will say barrels get damaged from improper cleaning and or not being cleaned enough as well as the barrel just flat out has too many rounds on it and the throat is so rough that it beats the bullet up and that causes a problem with the bullets blowing up and not a bullet issue per say. Other things can cause it.

Also guys running tight bore/tight groove barrels doesn’t help anything either. The tight bore type barrels will squeeze the bullet jacket more. If the lands are engraving deeper into a thin style match jacket type bullet....this is another reason for bullet failure. I don’t like tight bore barrels for this reason. For one they don’t shoot any more accurately than a standard bore/groove barrel and especially if shooting match type bullets.

Also you need to mention twist rates and velocities....My magic line in the sand is 300,000 rpm on the bullet. You approach or exceed this number and you can expect bullet failure. We all like speed and flat shooting bullets but you guys have to keep in mind that there are things that happen when we/you start pushing it more and more. No way around it.

How can the 5R style rifling help? The odd number of lands and grooves...the lands don’t directly oppose one another. So this will distort and upset the bullet jacket less and that helps fight the bullet failure.

Also Hornady showed ballistics test data last Sept. at the GAP Grind where they now have data to support that the 5R style rifling helps the bullets accuracy/flight especially when you hit the transonic range. The 4 groove and 6 groove barrels all showed the bullet fly funny when it hit the transonic range. (A shout out to Jayden at Hornady that did the presentation on ballistics at the GAP Grind. He shared a lot of information and explained it so guys could understand it. I sat in on the presentation not know what he was all going to talk about. It was nice to sit on the other side of the table for a change and listen and ask questions! Thanks Jayden!)

I’ve shot everything from 2 groove, (made 3 groove), 4 groove, conventional 5 groove, 5R, 6 groove, 8 groove in calibers from 22RF up thru .338 caliber and in the grand scheme of things really don’t see a accuracy difference in the real world.

Take what you hear with a grain of salt. You don’t always know the whole picture when a guy is having a problem and or what is really causing the problem.

Later, Frank
Bartlein Barrels
 
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Frank Green said:
You can ask several reputable smiths like Dave Tooley, George Gardner at GAP, Moon at Crescent Customs, Mark Gordon at SAC etc....

The whole chambering and chatter thing I don’t see it. We ourselves chamber in excess of a 1000 barrels a year and probably 60% of those are 5R style rifling and we don’t see any issues vs a 4 groove or 6 groove barrel.

I’ve maintained for several years now that the 5R style rifling does help fight bullet failure. Bullets can fail because the bullet can be a problem but with in saying that I will say barrels get damaged from improper cleaning and or not being cleaned enough as well as the barrel just flat out has too many rounds on it and the throat is so rough that it beats the bullet up and that causes a problem with the bullets blowing up and not a bullet issue per say. Other things can cause it.

Also guys running tight bore/tight groove barrels doesn’t help anything either. The tight bore type barrels will squeeze the bullet jacket more. If the lands are engraving deeper into a thin style match jacket type bullet....this is another reason for bullet failure. I don’t like tight bore barrels for this reason. For one they don’t shoot any more accurately than a standard bore/groove barrel and especially if shooting match type bullets.

Also you need to mention twist rates and velocities....My magic line in the sand is 300,000 rpm on the bullet. You approach or exceed this number and you can expect bullet failure. We all like speed and flat shooting bullets but you guys have to keep in mind that there are things that happen when we/you start pushing it more and more. No way around it.

How can the 5R style rifling help? The odd number of lands and grooves...the lands don’t directly oppose one another. So this will distort and upset the bullet jacket less and that helps fight the bullet failure.

Also Hornady showed ballistics test data last Sept. at the GAP Grind where they now have data to support that the 5R style rifling helps the bullets accuracy/flight especially when you hit the transonic range. The 4 groove and 6 groove barrels all showed the bullet fly funny when it hit the transonic range. (A shout out to Jayden at Hornady that did the presentation on ballistics at the GAP Grind. He shared a lot of information and explained it so guys could understand it. I sat in on the presentation not know what he was all going to talk about. It was nice to sit on the other side of the table for a change and listen and ask questions! Thanks Jayden!)

I’ve shot everything from 2 groove, (made 3 groove), 4 groove, conventional 5 groove, 5R, 6 groove, 8 groove in calibers from 22RF up thru .338 caliber and in the grand scheme of things really don’t see a accuracy difference in the real world.

Take what you hear with a grain of salt. You don’t always know the whole picture when a guy is having a problem and or what is really causing the problem.

Later, Frank
Bartlein Barrels
Click to expand...

Thanks for the taking the time to clarify especially on the chamber and transonic test.
 
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Welcome nick338!

Also forgot some stuff.....

How the chamber reamer is ground, speeds and feeds, type of cutting fluid a gunsmith uses can cause chatter issues as well. Also you can throw in a different lot of steel or a different type of steel.

I’ve had guys tell me the reamer is chattering? Really? What speed you running the lathe at? Oh...80rpm. Your to slow. Up the rpm of the lathe. Guess what....chatter stops.

Also think of this guys....not just Hornady but places like Federal Cartridge, Sierra Bullets, some of the different arsenals....where they have tested side by side say 4 groove and 5R rifled barrels in 308win, 300wm, 6.5CM, 6CM, 260 Rem, 223 Rem and I can name some more....with the exception of the recent testing Hornady did late last year that I mentioned and the transonic data that they seen....when these places tell me they don’t see an accuracy difference for the most part and they are shooting not a 100 or 500 but tens of thousands of rounds/bullets down the barrels in controlled conditions and have good data to back it up. That tells me more and can show us things than what one or two of us might see in shooting one barrel for a summer in some matches.

A few years ago the gov’t tested some where around 26 different 6.5mm bullets and shot them thru 5R rifling, 4 groove and 6 groove barrels and had no chambering issues with any of them. They didn’t just test one or two barrels. They tested a bunch.

Like I said you have to sit back and “when you hear certain things...take it with a grain of salt.”

Again the Hornady data is the most recent that I’ve seen and what it shows is interesting and they are not pimping this type or that type of rifling or this or that barrel maker. They are just looking at data and trying to solve issues like bullet failure etc...to make they’re bullets better/products better for everyone. I know the Sierra guys do the same things as well as others.
 
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Too much in the brain to get out at one time....One minor exception to the rule of accuracy and the number of grooves. If your building a 6PPC bench gun (which I know 99.9% of the guys on here are not) you don't want 5R rifling. You want conventional rifling. 4 groove, 5 groove, 6 groove etc...why? Those short jacket 6mm bullets (most bench guys are shooting 65-68gr bullets). That short jacket bullet doesn't have a lot of bearing surface for the lands to do the driving and it's worse with a boat tail bullet in 6mm. The hard edge of the lands on conventional rifling bites and drives the bullet better. With 5R rifling I tell guys you can expect accuracy in the high .2xx's to flat .3xx's. That's all you will get out of it. With conventional rifling you can get in the .1xx's and even .0xx's. My 5 groove 1-13.75 twist gun for the last 5 x 5 shot groups agg'd a .177". One group was a .098".

Now stay with 6mm and go to the long heavy bullets like 85gr and heavier they don't care.

Thinking about reamer chatter.....as an example we just had to chamber over 20+ test barrels in 6.5mm. The tools supplied by the customer. All 6 groove and 1-8 twist. The reamer(s) all chattered pretty good till you had about 4-5 barrels on it. Then the reamer settled down and cut really nice and smooth. Why? The way it is/was ground and could be in conjunction with how long/tall the flutes are as well. In this case I'll say the way they are ground.
 
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Frank Green said:
Too much in the brain to get out at one time....One minor exception to the rule of accuracy and the number of grooves. If your building a 6PPC bench gun (which I know 99.9% of the guys on here are not) you don't want 5R rifling. You want conventional rifling. 4 groove, 5 groove, 6 groove etc...why? Those short jacket 6mm bullets (most bench guys are shooting 65-68gr bullets). That short jacket bullet doesn't have a lot of bearing surface for the lands to do the driving and it's worse with a boat tail bullet in 6mm. The hard edge of the lands on conventional rifling bites and drives the bullet better. With 5R rifling I tell guys you can expect accuracy in the high .2xx's to flat .3xx's. That's all you will get out of it. With conventional rifling you can get in the .1xx's and even .0xx's. My 5 groove 1-13.75 twist gun for the last 5 x 5 shot groups agg'd a .177". One group was a .098".

Now stay with 6mm and go to the long heavy bullets like 85gr and heavier they don't care.

Thinking about reamer chatter.....as an example we just had to chamber over 20+ test barrels in 6.5mm. The tools supplied by the customer. All 6 groove and 1-8 twist. The reamer(s) all chattered pretty good till you had about 4-5 barrels on it. Then the reamer settled down and cut really nice and smooth. Why? The way it is/was ground and could be in conjunction with how long/tall the flutes are as well. In this case I'll say the way they are ground.
Click to expand...

Says a lot when someone in the thick of it finds the time to answer questions and educate. Thank you
 
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A&8's said:
Customer service = job security.
Click to expand...

Nice thought but I don't necessarily look at it that way.

I look at it this way....there is so much misinformation out there and BS I just try and bring facts to the table in a way everyone can understand it.

Sometimes I see a post on a thread and I'll chime in. Sometimes someone will see something or ask a question and ask me to make a post about it. I help when I can.

If you ask me a question and I have an answer and will tell you it's a fact. If my answer is based on my opinion I'll tell you what it's based on but throw in the variables because at times there can be so many variables there might not be a clear cut answer/definition as to what is going on.

If I don't know....I'll tell ya...I don't know!

Good example...when I started hi power shooting back in the late 80's a old timer (guess I'm dating myself now) walked up to me and said, "I see you have a c.m. barrel on your gun." I said yes it is. He then says, "you want s.s. it will last a 1000 rounds longer in 308win." I figured the guy knew what he was talking about. Been around a long time etc... but guess what. No real truth to it. Yes the c.m. vs. s.s. do wear differently but we've made ammunition test barrels in both materials did all the chamber work etc... for a ammunition maker and the last ones I can remember where 300wm. Guess what? No difference in barrel life. Did some in 7mm Rem. Mag as well. Again no difference.

I'm outta here for a bit....got to get some work done.
 
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Frank Green said:
Nice thought but I don't necessarily look at it that way.

I look at it this way....there is so much misinformation out there and BS I just try and bring facts to the table in a way everyone can understand it.

Sometimes I see a post on a thread and I'll chime in. Sometimes someone will see something or ask a question and ask me to make a post about it. I help when I can.

If you ask me a question and I have an answer and will tell you it's a fact. If my answer is based on my opinion I'll tell you what it's based on but throw in the variables because at times there can be so many variables there might not be a clear cut answer/definition as to what is going on.

If I don't know....I'll tell ya...I don't know!

Good example...when I started hi power shooting back in the late 80's a old timer (guess I'm dating myself now) walked up to me and said, "I see you have a c.m. barrel on your gun." I said yes it is. He then says, "you want s.s. it will last a 1000 rounds longer in 308win." I figured the guy knew what he was talking about. Been around a long time etc... but guess what. No real truth to it. Yes the c.m. vs. s.s. do wear differently but we've made ammunition test barrels in both materials did all the chamber work etc... for a ammunition maker and the last ones I can remember where 300wm. Guess what? No difference in barrel life. Did some in 7mm Rem. Mag as well. Again no difference.

I'm outta here for a bit....got to get some work done.
Click to expand...

You beat me to it. I found your responses completely unrelated to customer service and more just trying to pass on factual information to clear up any confusion.

If I buy one of your barrels and it won't shoot we can talk about customer service, until then hopefully you are willing to continue to keep some of us educated.
 
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Frank Green said:
Nice thought but I don't necessarily look at it that way.

I look at it this way....there is so much misinformation out there and BS I just try and bring facts to the table in a way everyone can understand it.

Sometimes I see a post on a thread and I'll chime in. Sometimes someone will see something or ask a question and ask me to make a post about it. I help when I can.

If you ask me a question and I have an answer and will tell you it's a fact. If my answer is based on my opinion I'll tell you what it's based on but throw in the variables because at times there can be so many variables there might not be a clear cut answer/definition as to what is going on.

If I don't know....I'll tell ya...I don't know!

Good example...when I started hi power shooting back in the late 80's a old timer (guess I'm dating myself now) walked up to me and said, "I see you have a c.m. barrel on your gun." I said yes it is. He then says, "you want s.s. it will last a 1000 rounds longer in 308win." I figured the guy knew what he was talking about. Been around a long time etc... but guess what. No real truth to it. Yes the c.m. vs. s.s. do wear differently but we've made ammunition test barrels in both materials did all the chamber work etc... for a ammunition maker and the last ones I can remember where 300wm. Guess what? No difference in barrel life. Did some in 7mm Rem. Mag as well. Again no difference.

I'm outta here for a bit....got to get some work done.
Click to expand...

AMEN. My same thought process and what I try to accomplish here at SH on a daily basis.
 
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Frank Green said:
Nice thought but I don't necessarily look at it that way.
Click to expand...
nick338 said:
You beat me to it. I found your responses completely unrelated to customer service and more just trying to pass on factual information to clear up any confusion.
Click to expand...


No disrespect intended @Frank Green . I do consider it customer service, since someone specifically stated, "... Maybe a rep from Bartlein can chime in here since that was where the info originated from..." IMO, customer service isn't just when a person has a problem, per say, with a product. Customer service is, just like when I called Bartlien yesterday to place an order. I spoke with Marty (I think that was his name) for a good long while after I placed my order about how things where going here, being an LEO (he asked). This had nothing at all to do with barrels or even shooting, for that matter. However, I considered it customer service, because he actually gave a shit about me, the customer.
 
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MikeRTacOps said:
Have been told by several builders including one that will only use a 4 groove barrel for builds that the 4 groove makes for a more accurate rifle

This is True 100% but what would I know ?

Mike R.
Click to expand...

Several things. If we have been told that there is no difference between 4 groove and 5R in most cases , would you like to share any data to support your reasoning on this? You seem very confident and I would like to hear why the 4 groove is more accurate.

And if there are minor differences, would they outweigh the claim that bullets shot from a 5R barrel handle the transonic speeds better than ones shot from a 4 groove.
 
MikeRTacOps said:
Have been told by several builders including one that will only use a 4 groove barrel for builds that the 4 groove makes for a more accurate rifle

This is True 100% but what would I know ?

Mike R.
Click to expand...

Mike,

Your reputation and your rifles speak for themselves. Care to elaborate or give us some info behind your statement? I am not 100% in the know of all the calibers you offer but I do know you are very well known for building LE/SWAT rifles in .308 to shoot 168gr bullets that are extremely accurate. Is this where you have found 4 groove shines? Or have you tested this across many calibers?

Just trying to get some substance to your statement for discussion.
 
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I believe Mike builds tactical/LE rifles. Guns that shoot in the .090- sub .250 w factory ammo. ELR is a different game.

I would like to hear from Dan Warner or Litz on this subject. I take anything to do w Hornady w a grain of salt.
 
Jon Beanland built my rifles and he says he prefers 4-groove because yes... 5R can cause chatter when reaming in some situations. Beanland's reputation speaks for itself and both of my rifles shoot great. I have no complaints. Doesn't matter which one I use. In the end, it comes down to what my smith prefers and is more comfortable working with.
 
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BCX said:
I believe Mike builds tactical/LE rifles. Guns that shoot in the .090- sub .250 w factory ammo. ELR is a different game.

I would like to hear from Dan Warner or Litz on this subject. I take anything to do w Hornady w a grain of salt.
Click to expand...

I talk to Al/Dan Warner quite a bit etc...give Dan a call and pick his brain!

A few/several years ago GAP got a order for like 200-250 guns for the FBI/HRT. We made all the barrels. All of the guns where 308win. Right before shot show George shipped the first 40 rifles. George test fired everyone of them. The 40 guns averaged a .190” if I recall correctly. George put the targets on a board and had them on display at Shot Show that year. All of those guns had 5R rifling. So where is the accuracy difference?
 
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We are using a spiral fluted reamer that PT&G made for use and it limits the chatter you would get from a straight reamer because it stays in contact with the riflings at all times a straight reamer falls on and off lands anyway the my 2 cents worth , but everyone has their own opinion .
 
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Its not rocket science 4 grove will support the front of a live pilot reamer more securely than 5 groove. Even less support of the lands are canted
(or what ever u want to call it) Spiral fluted reamer is the way to go. Carbide is even better. Chatter is only part of the problem. But I wont get into that
Be thankful that your Gunsmith is aware of this, It means he is on his game and looking at his work.
 
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Leonard Barnes said:
We are using a spiral fluted reamer that PT&G made for use and it limits the chatter you would get from a straight reamer because it stays in contact with the riflings at all times a straight reamer falls on and off lands anyway the my 2 cents worth , but everyone has their own opinion .
Click to expand...

So you are saying that when a reamer "chatters" under a load, it is because of its engagement in and out of the lands it is cutting away?

./
 
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Terry Cross said:
So you are saying that when a reamer "chatters" under a load, it is because of its engagement in and out of the lands it is cutting away?

./
Click to expand...

I believe that is what he is saying. It has been explained to me several times in the last few days that the flutes on a conventional reamer make contact evenly with a 4 groove barrel but is not able to do so on a 5R because there is no opposing land as the flute pushes off on one side causing the reamer to cant slightly while cutting. This is what is often referred to as "chatter" and can lead to chamber that is not completely concerntric. Not really sure if it has actual affect on accuracy but that is how it was explained.
 
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lloydx2 said:
Its not rocket science 4 grove will support the front of a live pilot reamer more securely than 5 groove. Even less support of the lands are canted
(or what ever u want to call it)
Click to expand...

Please elaborate....


The tops of each land is simply the remnants of the original drilled/reamed/lapped hole that was used to guide the carbide tooth that cuts the grooves.

So.....the top of each land is one of the most perfect and consistent features in a rifled bore. The tops of the lands in any bore profile (except maybe some of the odd button rifled profiles like the "ratchet rifling") would be exceptionally concentric to any other features, exceptionally uniform in surface qualities and be an exceptionally true round profile. Accordingly the top of each land is not a "point" of contact but an entire area of contact.

The top surface of a single groove in a 3 groove bore will be wider than the same top surface of a single groove in a 4 groove bore, but cumulatively the total surface support stays roughly the same. Remember also that each surface has the exact radius that the reamer guide is supposed to be matched to so the total available top groove surface is potentially in play.

Regardless of how many grooves a barrel has, the reamer support would be roughly equal across the board assuming you have a everything else properly set up.

Caveat: I do not manufacture barrel blanks. Just cut chambers in them. If I had $10 Million in the best barrel making machines in the shop, it would likely be 10 years before I could even get close to the art that our top makers are consistently kicking them out with. Hats off to the real experts at Krieger, Bartlein and a few others for their incredible products and expertise.


./
 
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nick338 said:
I believe that is what he is saying. It has been explained to me several times in the last few days that the flutes on a conventional reamer make contact evenly with a 4 groove barrel but is not able to do so on a 5R because there is no opposing land as the flute pushes off on one side causing the reamer to cant slightly while cutting. This is what is often referred to as "chatter" and can lead to chamber that is not completely concerntric. Not really sure if it has actual affect on accuracy but that is how it was explained.
Click to expand...

So wouldn't 3 groove barrels exhibit the same chatter for no other reason than they have no opposing land to each?

I am tracking with their argument but do not agree in practice. (I'm prolly way wrong).
Hear me out and I am all ears to counter any of my thinking.

Cutting away the actual lands is an incredibly small load on the reamer when cutting a chamber.
You can see it/feel it/measure it when using just a throater to adjust lead. If you are running a manual machine with high RPM, good coolant and sharp tooling, the feedback from cutting is almost non-existent. You are doing an interrupted cut that is only taking 0.003-0.004" of an existing feature away. When taken in the context of what the rest of the reamer is having to engage and cut at the same time, this is an exceptionally small share of the load.

I would argue that the majority of "load" on a reamer is from pushing the shoulder datum feature forward. The consistent and clean engagement between that part of the reamer and the uncut barrel material likely drives any other harmonic issues that may be seen as chatter.

With most chambering reamers having 6 flutes and the tops of each barrel's lands having a substantial width, in practice there seems to be a consistent and balanced engagement regardless of the number of bore grooves.

Just my 2 cents.


./
 
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Terry Cross said:
So wouldn't 3 groove barrels exhibit the same chatter for no other reason than they have no opposing land to each?

I am tracking with their argument but do not agree in practice. (I'm prolly way wrong).
Hear me out and I am all ears to counter any of my thinking.

Cutting away the actual lands is an incredibly small load on the reamer when cutting a chamber.
You can see it/feel it/measure it when using just a throater to adjust lead. If you are running a manual machine with high RPM, good coolant and sharp tooling, the feedback from cutting is almost non-existent. You are doing an interrupted cut that is only taking 0.003-0.004" of an existing feature away. When taken in the context of what the rest of the reamer is having to engage and cut at the same time, this is an exceptionally small share of the load.

I would argue that the majority of "load" on a reamer is from pushing the shoulder datum feature forward. The consistent and clean engagement between that part of the reamer and the uncut barrel material likely drives any other harmonic issues that may be seen as chatter.

With most chambering reamers having 6 flutes and the tops of each barrel's lands having a substantial width, in practice there seems to be a consistent and balanced engagement regardless of the number of bore grooves.

Just my 2 cents.


./
Click to expand...

Terry that's a good way to look at it and you bring up some good points and I'll throw this in as well....

We've done 7 groove 50cal barrels vs. the standard spec. of 8 groove. Again no difference in chambering/chatter because of the number of grooves.

And when we've done those 7 groove 50cal barrels...it's not just one or two. The order is usually like 200-400 of them.

Again we do 8 groove 50cal test barrels on and off thru out the year and mostly ammunition test barrels. Again don't see a difference in chambering because of the number of grooves.

For reference we have made and chambered barrels in 2 groove (don't ask for one LOL!), 4 groove, 5 groove, 5R, 6 groove, 7 groove, 8 groove, 10 groove, 12 groove and in calibers ranging from 22RF up thru 20mm.

Yes we've made 3 groove barrels as well but never chambered any of those here personally.

Also as Terry has mentioned usually you have basically the same amount of land/surface area supporting the pilot of the reamer. So what does the number of grooves have to do with it? In cases where there is no industry standard for like a 7 groove or 3 groove barrel or even a 10 groove per say we will pick a caliber that is a standard and make the land to groove ratio the same. Why? Nothing to do with chambering but the overall total of the bore surface area we have to maintain usually a specific ratio as the total surface area of the bore can have an effect on pressures and velocities.
 
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Terry Cross said:
So wouldn't 3 groove barrels exhibit the same chatter for no other reason than they have no opposing land to each?

I am tracking with their argument but do not agree in practice. (I'm prolly way wrong).
Hear me out and I am all ears to counter any of my thinking.

Cutting away the actual lands is an incredibly small load on the reamer when cutting a chamber.
You can see it/feel it/measure it when using just a throater to adjust lead. If you are running a manual machine with high RPM, good coolant and sharp tooling, the feedback from cutting is almost non-existent. You are doing an interrupted cut that is only taking 0.003-0.004" of an existing feature away. When taken in the context of what the rest of the reamer is having to engage and cut at the same time, this is an exceptionally small share of the load.

I would argue that the majority of "load" on a reamer is from pushing the shoulder datum feature forward. The consistent and clean engagement between that part of the reamer and the uncut barrel material likely drives any other harmonic issues that may be seen as chatter.

With most chambering reamers having 6 flutes and the tops of each barrel's lands having a substantial width, in practice there seems to be a consistent and balanced engagement regardless of the number of bore grooves.

Just my 2 cents.


./
Click to expand...

Based on their reasoning the answer is yes to any odd number of grooves, but I don't chamber barrels or measure them for concentricity so I can't support it with facts either way. At this point until someone can prove there is an actual difference in chamber measurements and that it affects accuracy, the theory of the 5R barrel engraving the bullet less aggressively and allowing better transonic performance carries more weight for me.
 
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lloydx2 said:
Its not rocket science 4 grove will support the front of a live pilot reamer more securely than 5 groove. Even less support of the lands are canted
(or what ever u want to call it) Spiral fluted reamer is the way to go. Carbide is even better. Chatter is only part of the problem. But I wont get into that
Be thankful that your Gunsmith is aware of this, It means he is on his game and looking at his work.
Click to expand...
Would you care to enlighten us all as to how either a 4 or a 5 flute barrel supports the live pilot any better than the other? I have whipped up a sketch (below) to roughly illustrate how a live pilot fits into the bore. How exactly does what you are saying work? Feel free to draw on the sketch to show forces that would allow the pilot (in either case) to move away from dead center.

I am always willing to learn and since it’s not rocket science, maybe I’ll even understand it. Thanks.

02FFE153-2C77-4363-8708-26168FA3E68D.png


P.S. I’ve exaggerated the lands for illustrative purposes and obviously the barrel thickness is not to scale.
 
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lash said:
Would you care to enlighten us all as to how either a 4 or a 5 flute barrel supports the live pilot any better than the other? I have whipped up a sketch (below) to roughly illustrate how a live pilot fits into the bore. How exactly does what you are saying work? Feel free to draw on the sketch to show forces that would allow the pilot (in either case) to move away from dead center.

I am always willing to learn and since it’s not rocket science, maybe I’ll even understand it. Thanks.

View attachment 7354207

P.S. I’ve exaggerated the lands for illustrative purposes and obviously the barrel thickness is not to scale.
Click to expand...
Nice diagrams, how about putting the reamer flutes, the clearance between the lands and the pilot, and the clearance between the pilot and reamer in them.
 
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Edds said:
Nice diagrams, how about putting the reamer flutes, the clearance between the lands and the pilot, and the clearance between the pilot and reamer in them.
Click to expand...
I’m sure that you would be better at that than I would. As I said, these are sketches. And how exactly would that change the answer to my question?

It’s a very straightforward question.
 
padom said:
Mike,

Your reputation and your rifles speak for themselves. Care to elaborate or give us some info behind your statement? I am not 100% in the know of all the calibers you offer but I do know you are very well known for building LE/SWAT rifles in .308 to shoot 168gr bullets that are extremely accurate. Is this where you have found 4 groove shines? Or have you tested this across many calibers?

Just trying to get some substance to your statement for discussion.
Click to expand...


I had a lengthy, in-depth conversation with @MikeRTacOps today

He confirmed his statement above, in his professional opinion and experience pertains to his bread and butter 308 LE guns shooting SMK bullets that he is very well known for. They shoot the tightest (one hole) with 4 groove barrels. His statement was not a blanket statement across all calibers. He has tested 5R barrels with the SMK factory ammo in his 308 TacOps rifles and they shot great he said, but not quite as tight as the 4 grooves.

Mike can comment further if he wishes but that was the recap of our conversation
 
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padom said:
I had a lengthy, in-depth conversation with @MikeRTacOps today

He confirmed his statement above, in his professional opinion and experience pertains to his bread and butter 308 LE guns shooting SMK bullets that he is very well known for. They shoot the tightest (one hole) with 4 groove barrels. His statement was not a blanket statement across all calibers. He has tested 5R barrels with the SMK factory ammo in his 308 TacOps rifles and they shot great he said, but not quite as tight as the 4 grooves.

Mike can comment further if he wishes but that was the recap of our conversation
Click to expand...

In a previous post it was mentioned that Mikes guns shoot .090” to .250” groups with box ammo.

So I’ll ask the question again from one of my previous post.

...A few/several years ago GAP got a order for like 200-250 guns for the FBI/HRT. We made all the barrels. All of the guns where 308win. Right before shot show George shipped the first 40 rifles. George test fired everyone of them. The 40 guns averaged a .190” if I recall correctly. George put the targets on a board and had them on display at Shot Show that year. All of those guns had 5R rifling. So where is the accuracy difference?

So .090” to .250” (lets take an average of Mikes range and call it .170”) and 40 guns built by GAP average a .190”. Again where is the difference? Your talking .020”.

If you all really knew what ammo/bullets where tested for an accuracy spec the .020” difference is negligible. I can tell you the ammo/bullets will be the limiting factor in accuracy. Even an above average shooter out in the environment will not see or hold a .020”. I know of match bullets that the accuracy spec. Is .333”moa. Some lots will shoot .250moa. Not all but some! There is a big difference between .333” and .250”.

I don’t care who builds the guns or what style of rifling....if you put that amount of guns together and I don’t care if it’s 40 at a time, 40 in a year or a 1000 in a year etc..your getting results in that area is awesome. I’ll tip my hat to Mike, George, Tooley, Warner, Whidden, Moon and right on down the line.

Mark at work just put two and we only made two 6mm CFW barrels for his benchrest guns and tested the barrels Tuesday of this week. Smallest group was .070”. Largest group was a .198 (4 of those rounds measured a .101”). So lets say either of Marks two guns will shoot a flat .100”! What happens outside in match conditions etc...I’ll tell you shooting 300 rounds in a match he would be lucky to agg a .150”. (Don’t be mad at me Mark).

When a guy tells Mark his gun will shoot .250” moa all day long....Mark says bring it to the Nationals or Supershoot you will cream everyone there! Funny nobody ever takes Mark up on his challenge?

Mark currently holds two or three world records in short range bench!
 
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