5R vs 4 Groove

[AccuSol-ERN]

Not to get sideways but I think most of you are looking at it incorrectly. The "chatter" that people are talking about doesn't really have anything to do with live pilot fitment (except in absurd mis-sizing examples), it has everything to do with an interrupted cut and not having reamer support 180 degrees opposite of the shearing edge of the reamer flute.

This is absolutely real......I check and verify this on every barrel. I can say with 100% certainty that "chatter" is less or non-existent on 4 groove and even better 6 groove barrels. In truth, you would probably eliminate this issue with a 5 flute reamer. I know a few other builders who use 5 flute throaters for this very reason.......especially since you don't have the support of the rest of the reamer being under load. Throaters are prone to "chatter" especially as they get a little wear.

You can avoid this issue (even on 5Rs) with pre-boring, sharp reamers, and I prefer super stiff carbide reamers (to avoid tooling flex).

The reason why results have been so hit and miss is because if you are using new/sharp reamers.......you can sit there and scrape away at the "chatter" and it removes material (not the case with slightly worn reamers). This also applies to shops that use CNCs to ream chambers.......you can dwell at full plunge and beat the "chatter" into submission with RPM and rigidity.

As Frank mentioned tool geometry plays a role in this as well......but I typically see this as a variable that I can't really control.....so I prefer the methods I mentioned above because it can be applied to ALL barrel configs and ALL reamer configs......kinda Best Practices in chambering.

Also, there have been many shops that have had issues with this that either don't check for it......or it has been blamed on "out of spec reamers".

I don't know if this issue effects accuracy or not.....I have personally seen (big name) rifles that shoot great but the customer says it has "zero" freebore....because the freebore diameter has so much "chatter" it is not full dimension.....so their Hornady COAL setup can't push a bullet up to the lands.

I prefer 4 (or 6) grooves for this reason......do 5Rs have merit?......probably......I refer you to Frank Green as the SME on that.

I hope this helps.

Ern

 

[Shooter71]

In my experience what we’re calling chatter is more like a five-count oscillation or harmonic, approximately a tenth high or so, that an indicator will pick up.

 

[AccuSol-ERN]

Shooter71......that's it......except at times it is MUCH worse than a tenth high or so......if you don't know about it and account for it.

Especially on reamers that are spec'd with freebore diameters of .0002" or even less over bullet diameter.

Does this "chatter" HURT accuracy? I don't know.........Does this "chatter" HELP accuracy? I don't see how it can.

Ern

 

[lash]

Not to get sideways but I think most of you are looking at it incorrectly. The "chatter" that people are talking about doesn't really have anything to do with live pilot fitment (except in absurd mis-sizing examples), it has everything to do with an interrupted cut and not having reamer support 180 degrees opposite of the shearing edge of the reamer flute.

This is absolutely real......I check and verify this on every barrel. I can say with 100% certainty that "chatter" is less or non-existent on 4 groove and even better 6 groove barrels. In truth, you would probably eliminate this issue with a 5 flute reamer. I know a few other builders who use 5 flute throaters for this very reason.......especially since you don't have the support of the rest of the reamer being under load. Throaters are prone to "chatter" especially as they get a little wear.

You can avoid this issue (even on 5Rs) with pre-boring, sharp reamers, and I prefer super stiff carbide reamers (to avoid tooling flex).

The reason why results have been so hit and miss is because if you are using new/sharp reamers.......you can sit there and scrape away at the "chatter" and it removes material (not the case with slightly worn reamers). This also applies to shops that use CNCs to ream chambers.......you can dwell at full plunge and beat the "chatter" into submission with RPM and rigidity.

As Frank mentioned tool geometry plays a role in this as well......but I typically see this as a variable that I can't really control.....so I prefer the methods I mentioned above because it can be applied to ALL barrel configs and ALL reamer configs......kinda Best Practices in chambering.

Also, there have been many shops that have had issues with this that either don't check for it......or it has been blamed on "out of spec reamers".

I don't know if this issue effects accuracy or not.....I have personally seen (big name) rifles that shoot great but the customer says it has "zero" freebore....because the freebore diameter has so much "chatter" it is not full dimension.....so their Hornady COAL setup can't push a bullet up to the lands.

I prefer 4 (or 6) grooves for this reason......do 5Rs have merit?......probably......I refer you to Frank Green as the SME on that.

I hope this helps.

Ern

I’ll buy this explanation for a dollar. It makes sense and fits with what I know from machining production parts on CNCs. I cannot judge whether or not one is better than the other, having neither the gunsmithing experience nor the experience with both types of barrels to do so. I just wasn't buying the pilot thing.

Since I personally do not shoot benchrest, it’s all really academic to me and I’ll continue to buy what works for me

 

[Steel head]

Perfect reference sketch you "whipped" up. You whipped it excellently. In fact you whipped it good.
View attachment 7354240

Seriously. Good visual. Thanks.

./

 

[1moaoff]

I point that I think needs to be made.
We are not on accurate shooter site.
For most of our purposes you cant tell the difference.

Mike R has an impeccable reputation and experience level. He may have more finite information on his specific build types over years.

Can there be a finite gain in certain scenarios? I would guess the answer is yes. Are some builders capable of that level of knowledge and do they have historical information to base their observations on? I would think so.

Would a 3 4 or 5 grove be more likely to have chatter? I dont think so but my knowledge is not as great as many here.

We have a ton of new guys and I hate to see them obsess over something most of them are unlikely to ever know the difference.

It really is an impressive amount of knowledge here.

 

[Frank Green]

To go back to reamers and chatter/that high frequency squeal.....again we had to do a job for 20+ test barrels and all 6 groove and 6.5mm. Customer supplied the tools...they where not ground correctly (also sprial flute) wouldn't even cut. Got new ones sent to us. They cut but for the first 4-5 barrels had the high frequency squeal. After a few barrels the reamers would settle down and cut like a dream. It was how the reamers where ground. Had nothing to do with the number or style of grooves!

 

[AccuSol-ERN]

Yeah the high pitch squeal chatter (most of the time with new reamers) is not the "chatter" that is referred to here.

What is referred to in this thread is honestly not the vibratory chatter we are used to......it is interrupted cut and tool flex/movement/whatever.

Ern

 

[AccuSol-ERN]

So in the end I think there is no REAL answer to which is better 4 or 5R...….to the original question. They each have their pros and cons.....

So long as the builder doing your work understands (and knows how to remedy) the pros and cons of both...…..you will NEVER to able to shoot the difference.

Run which ever gives you a warm and fuzzy......you will probably see more of a difference on target between high/low confidence in your rifle.

Ern

 

[Frank Green]

So in the end I think there is no REAL answer to which is better 4 or 5R...….to the original question. They each have their pros and cons.....

So long as the builder doing your work understands (and knows how to remedy) the pros and cons of both...…..you will NEVER to able to shoot the difference.

Run which ever gives you a warm and fuzzy......you will probably see more of a difference on target between high/low confidence in your rifle.

Ern

I'll say it again here and this is what I tell everyone...."for the most part the style or number of grooves has no real bearing on accuracy and or barrel life. The more uniform the bore and groove sizes are over the length of the barrel, the more uniform the twist, the straighter the blank and the more stress free it is...the more forgiving the barrel is going to be!"

What I said I stand behind on the 5R and I know Boots pushed it for years as well. I do feel it does help fight bullet failure. It does nothing for velocity or pressure as some have said etc....

Also when bullets fail it can be due to other reasons and not just the barrel or the bullet.

Too much velocity, too much twist, too many rounds on the barrel, amount of rounds in between cleaning, damage to the barrel from improper cleaning, damage to the barrel for gunsmithing etc...

I'm outta here for the weekend! You guys have a Happy Fathers Day!

Later, Frank

 

[AccuSol-ERN]

Happy Father's day to you too Frank (and others).

It is such a privilege to bounce ideas/experience off some of the best subject matter experts in the industry.

Ern

 

[Frank Green]

Here some pictures for your viewing pleasure....first one is of Mark's new CFW barrels in 6PPC. We made him only two and he test fired them last week Tuesday. No load tuning etc...put 15 rounds thru each gun. Three 5 shot groups. One group is missing as he used a different target just to check that the guns where still on paper.

The last picture is of his target that holds the current world record for 10 shots in the unlimited class at 100 yards. Like the target says....that's a .104" for 10 shots. Not pictured is his other current world record group is a .081" for the light gun class. Those barrels are 5 groove.

Guess what barrels are on his cfw that we just made him?

Later, Frank

 

[Frank Green]

Nobody wanted to guess on the number of grooves on Marks CFW barrels hey?

We made those 4 groove.

Why? That's the tooling that was in the rifling machine at the time. That's the only reason.

No difference in accuracy.

 

[AccuSol-ERN]

Well......that's because 4 grooves are better.....everyone knows that.....ha.

Ern