Barrel Specs 101 -- importance of various specs, with bullet type and weight

[BlueWater]

Am looking for a "Barrel Specs 101" type summary of the details of barrel selection, when re-barreling for, say, the 6BR caliber. If there's a great technical summary, someplace, I'm all for it. (Haven't found one, yet.)

Assumptions:
6BR caliber
Heavier, longer, VLD-type bullets preferred (100-115gr 6mm)
Distances in the 300-1000yd range


Twist rate -- I appreciate that the twist-rate needs to be fast enough to stabilize. But, is there an "optimal" range of twist-rate that'll work for certain bullet weights? Can a twist-rate go too fast, for 6BR? (ie, Some bullet makers might suggest 1:7.75" twist for a 6mm bullet of a given weight, but a barrel maker might only do 1:8" twist and 1:7" twist.) Don't understand what the limits are, here, with twist-rate.

Groove count -- With the 6BR, is there a typical or preferred groove count (ie, 4, 5R, 6) that people choose for the heavier, VLD-type bullets? The barrel makers seem to offer two or three different groove counts for the caliber. Uncertain which would make sense, depending.

Bore diameter -- (ie, .237" or .236".) Is the bore diameter going to matter that much, for a given maker, model, weight of bullet selected? For example, a Berger 108gr Hybrid Target (VLD) versus a Sierra 107gr MK versus a Bart's 103gr Hammer (VLD), etc. Do certain bullets seemingly "prefer" this or that bore diameter?

Freebore -- How important is freebore choice, if the heavier (100-115gr), longer, VLD-type bullets are going to be used? Is there a preferred freebore, where this type of 6BR bullet seems to perform better?

Barrel contour/diameter -- Plenty of choices. Uncertain to what degree, if any, barrel diameter and profile selection makes with respect to bullet performance, in the heavier-VLD, longer-distance arena. (I'm assuming, say, a lighter-weight profile 28" barrel will behave a bit differently than a heavy-Palma or straight-contour 28" barrel of similar make, but I don't know.)

Insights? A "Barrels 101" write-up somewhere?

 

[JMayo]

IMO
It's according to what game you're playing.
Go to matches talk to the top shooters or the guy that builds their rifles.
I chose 600 yrd. Got the info about a good GSmith and started the conversation.
.... Mostly I said " I don't know what do you suggest ....."
I've improved every year, the rifle is top notch.

I met short range guys at the 600yd. Ask questions, called the GSmith again I let him lead ... I've done well, the rifle is top notch.

Now I own several rifles all unique to the game played with them.

Now bullet, powder, scale, brass, primer, press, seater ..... THAT'S A BIG HOLE TO DIVE INTO

 

[BlueWater]

Go to matches talk to the top shooters or the guy that builds their rifles ...

Sure. But, here we are. So I'm asking it here.

Not doing competition, myself. While I appreciate there are many who do, I would think that many with such experience are here as forum members and can provide a bit of appropriate guidance on the key barrel features, as to how they might impact what's being shot through them. I simply don't appreciate, yet, whether these (or other) factors are vital ... and how they are, beyond twist-rate (which is the only thing I've specified previously).

 

[wkdickinson]

IMO I think you are looking for something that doesn't and/or can't exist. The twist rate is pretty "cookbook", go to Berger Bullet's "Twist Rate Stability Calculator" and in a few minutes you will know what twist rate you need for the range of bullets you want to shoot. The barrel contour is really more a function of the gun's purpose as JMayo suggested. You say you aren't going to compete, so you have to define what you are building the rifle to do and weight will likely define the contour. Your other 3 criteria are so controversial you well never anything that gives your the "right" answer. If you spend much time researching those subjects on this forum, you will find about as many different opinions as there are members.

 

[BlueWater]

Said what my intentions are: decent accuracy from 300-1000yds. Not competition level exacting perfection, no. But on aspects or features of a re-barreling as to what I'd want to specify to the maker to do ... that's what I'm wanting to know more about.

I appreciate basic twist-rate. Just not with what's typical in practice with 6BR. I understand the basic bullet makers indicate a certain twist is recommended, and that the Berger site has the stability calculator, etc. Uncertain what individuals are typically choosing for twist, in practice with 6BR. The makers will generally state what a minimum is. But in practice it might well be that people who shoot 6BR are going a bit faster, for certain bullets. Hence the question here.

Profile, per se, might not be so important to some. But the profile+diameter should alter the amount of heating a barrel will be subjected to, and how fast, as well as to a degree change how whippy versus stable a barrel's harmonics might be. Don't know if those differences from, say, a light hunting profile versus a 1.5" diameter straight barrel will be vital, with 6BR. Hence the question on profile/diameter. If in practice most people doing 300-1000yd non-competitive accurate target shooting are selecting for 6BR, say, a heavy Palma profile of a given length and diameter, then that'd be useful to know. (The equipment lists published about various competitions generally speak of brands of things, not specifics like this.)

Freebore might be controversial with some, but I'd like to appreciate the freebore question and why people tend to choose it a certain way. Most write-ups I've found speak of it passingly, but not much else.

Don't intend to spend oodles of time "researching" these. Thought getting some feedback on practical choices people are making, for re-barreling 6BR, would be worthwhile.

In the end, perhaps people just call the barrel makers and ask for X twist of Y length, and call it good. Which is fine, too, if that's people's actual experiences with a 6BR setup for non-competitive target use. I suspect, though, that with the several discussions that occur monthly regarding detailed specs on barrels and chambers that it's more than that.

Perhaps I should have asked more simply: when re-barreling for 6BR, what specs do people typically worry about and select, when directing the barrel maker to make it a certain way.

 

[jelenko]

You still need to say at least what 'decent accuracy' means for you.
There's a different answers for 1.5 MOA hunting rifle, 0.5 MOA PD hunting, .3 MOA F class competition rifle, 0.15 MOA benchrest or .75 MOA cross the course rifle.

 

[Walt Krafft]

3,4,5,6 groove will all shoot. Both .236 and .237 bore will shoot. The twist is determined by the heaviest bullet you want to shoot. If one was that much better than the others, we would all be using it.

 

[BlueWater]

You still need to say at least what 'decent accuracy' means for you.
There's a different answers for 1.5 MOA hunting rifle, 0.5 MOA PD hunting, .3 MOA F class competition rifle, 0.15 MOA benchrest or .75 MOA cross the course rifle.

We're speaking of 6BR. It's benchrest. It's for long-range target shooting out to 1000yds. Intention is for frequent 300-500 with occasional 500-1000yd shoots. So, short of competitive accuracy but fairly accurate would be the goal. I'm fairly unfamiliar, as yet, with 6BR as a caliber. Little experience shooting it.

Accuracy I've achieve previously on different platforms: between 1/4 and 1/3 MOA with .243 at 300yds. So I'm capable of it. Assuming the rifle's up to snuff.

In 6BA I'm fully expecting that, if I go that caliber. Would love to achieve 1/3 MOA at 1000yds eventually as well, but that might be a stretch. 1/2 MOA is probably more likely as a goal. I'd be pretty steamed, after a year of tuning and focus to only end up with 10" group sizes at 1000yds, but that's me.

So. A fairly exacting barrel maker, tight processes and tolerances, fitted properly, bedded properly. Not to competition grade, perhaps, but still vastly beyond the average off-the-shelf hunting rifle.

Again, looking to understand what people who care about the barrel technical specifics look at, when doing a re-barrel in 6BA. I'm all for just specifying twist-rate to a maker, but it's clear that people on this forum deal with far more than just that when doing a re-barrel and chambering. Looking for a summary on these aspects and why people specify them for a given barrel.

 

[Stan Taylor]

Well here goes from me 90% of the 6br barrels that I install are an 8 twist and most of those people ARE shooting 105 grain class bullet.
I am quite sure someone will contradict what I just said.
If you go with a straight taper barrel of about .950 muzzle no longer than 28 inches you can achieve anything you want.

 

[BlueWater]

Well here goes from me 90% of the 6br barrels that I install are an 8 twist and most of those people ARE shooting 105 grain class bullet.
I am quite sure someone will contradict what I just said.
If you go with a straight taper barrel of about .950 muzzle no longer than 28 inches you can achieve anything you want.

Have you done a 6BR re-barrel or specified a barrel from a maker where you were particular with any other technical aspects of that barrel's prep? Or, just twist-rate and contour, and left the rest up to "normal BR" choice by the maker and chamberer?

 

[snert]

Stan is from Douglas barrels and is an old hand.

 

[HTSmith]

I would sure listen to Stan since he's in the barrel making business. My $.02 is below:
Twist rate -- I appreciate that the twist-rate needs to be fast enough to stabilize. But, is there an "optimal" range of twist-rate that'll work for certain bullet weights? Can a twist-rate go too fast, for 6BR? (ie, Some bullet makers might suggest 1:7.75" twist for a 6mm bullet of a given weight, but a barrel maker might only do 1:8" twist and 1:7" twist.) Don't understand what the limits are, here, with twist-rate. 8 is the go to. I have one 7.5 because that is what the gunsmith had on hand. It does fine too. I don't shoot anything heavier than a 108 Gr. Berger.

Groove count -- With the 6BR, is there a typical or preferred groove count (ie, 4, 5R, 6) that people choose for the heavier, VLD-type bullets? The barrel makers seem to offer two or three different groove counts for the caliber. Uncertain which would make sense, depending. I don't think it really matters. I've got 4, 5R, and 6.

Bore diameter -- (ie, .237" or .236".) Is the bore diameter going to matter that much, for a given maker, model, weight of bullet selected? For example, a Berger 108gr Hybrid Target (VLD) versus a Sierra 107gr MK versus a Bart's 103gr Hammer (VLD), etc. Do certain bullets seemingly "prefer" this or that bore diameter? Don't really think that matters much either. I've got both. Seems like the 237's will take a little more powder but that could be my imagination.

Freebore -- How important is freebore choice, if the heavier (100-115gr), longer, VLD-type bullets are going to be used? Is there a preferred freebore, where this type of 6BR bullet seems to perform better? Personally (some will disagree), I don't think the 6BR has the boiler room for the real heavy bullets. It's happiest at 108 Gr and under. It also has a long neck that is very forgiving. I've got from .060" to .105" freebore. The .060" is a wee bit short. I finally bought a reamer with a .105" freebore and it works very well with 103 to 108 gr bullets.

Barrel contour/diameter -- Plenty of choices. Uncertain to what degree, if any, barrel diameter and profile selection makes with respect to bullet performance, in the heavier-VLD, longer-distance arena. (I'm assuming, say, a lighter-weight profile 28" barrel will behave a bit differently than a heavy-Palma or straight-contour 28" barrel of similar make, but I don't know.) I prefer the HV contour for pure target rifles. I do have a Remington Varmint weight barrel on a rig that I take out for varmints and deer. It shoots way better than me and is semi portable. Here's where a good 'Smith can help, because you don't want a real muzzle heavy gun.

These are just my own somewhat educated opinions. Like I said, when someone like Stan spoke I would listen. Have fun with it.

 

[JFrank]

Well here goes from me 90% of the 6br barrels that I install are an 8 twist and most of those people ARE shooting 105 grain class bullet.
I am quite sure someone will contradict what I just said.
If you go with a straight taper barrel of about .950 muzzle no longer than 28 inches you can achieve anything you want.

Have you done a 6BR re-barrel or specified a barrel from a maker where you were particular with any other technical aspects of that barrel's prep? Or, just twist-rate and contour, and left the rest up to "normal BR" choice by the maker and chamberer?

Stanley may know a thing or two about barrels.

 

[BlueWater]

View attachment 1275114Stanley may know a thing or two about barrels.

Am not aware of the various "names" in the industry. Wasn't clear on Stan's post that he's a barrel maker, though most here seem to know it.


Still interested in everybody's experiences when they're specifying details on barrels they get made.

 

[BlueWater]

Not sure what more you would need

Not sure, either. Hence the questions for people's experiences on finished barrels.

 

[Stan Taylor]

Not sure, either. Hence the questions for people's experiences on finished barrels.

In my year's of reading this forum I don't comprehend what is so important in your needs.
Here is a match report from a couple weeks ago the gentleman name Rick Smith his second year shooting one gun in a 1000 yd State match finishes 5th place in the 2gun group and 3rd. In 2gun overall.
4Light gun 5 shot groups, 4 HG 10 shot groups had 3/4 moa for 8 target shooting against 6Bra,and 6 Dasher,300wsm with an 8 twist barrel I installed for him and it was a 6 groove .237 bore.

 

[Liven The Dream]

I have a 6 Norma Dasher built by Randy Gregory in Wisconsin.
This is a F/Open Rifle , Barrel He Supplied SS Krieger ( Obermeyer 5R) 1-7.5 #17 Contour Finish at 30" .
Have only shot it out to 600 Yards on F/Class Target . I use Varget , CCI450 and Berger 105HB.
Have 103 Vaper Tails not shot in a Match.

Last Match at 600 1 string 200-16 them 199-10 and 198-12
I shot the 9 in the 199 ?

Best of Luck

I had a Guy tell me 1-7.5 would not work ?

 

[BlueWater]

In my year's of reading this forum I don't comprehend what is so important in your needs.

I've seen numerous discussion threads, on this and other similar "long-range shooting" type forums, where a number of features beyond mere twist-rate and profile gets discussed. Some don't care, and let the barrel maker choose nearly everything. Some get down to a gnat's eyebrow on specs, all the way to the least question related to chambering.

Me, I'm simply looking for a "Barrel 101" summary of what people are bothering with, when getting a new barrel spec'ed and installed. I don't know whether some of the details are pointless and superfluous. I'm trying to separate the wheat from the chaff, so to speak, with a "Barrel 101" from people's experiences.

If it turns out all one truly needs to communicate is twist-rate and, profile and length, great! Then people can say that. I'm just coming from the perspective that all those discussion threads kicking around other details and aspects of barrels come from somewhere, that perhaps in people's experience some of those matter. (Don't know, myself, as I've only done a re-barrel, years ago, where I just worried about twist.)

 

[swd]

You aren't going to to shoot the difference between a 7.5" and 8". Slightly more stability is always better then slightly not enough but in your case either will more than enough to get the job done unless you decide to try one of the heavier bullets which really don't suite the straight 6BR.

.236"-.237" flip a coin. I have both and both win matches. I get the same speeds from both. Zero difference in accuracy.

# of grooves, again records have been set with all of them. Pick one of the top tier barrel makers and go with whatever they specialize. They have dome their R&D to make their preferred number of groves work. Ford, Chevy, Dodge. You just have to pick one.

Contour, no effect on accuracy as far as the barrel is concerned but weight is moderately important for how the rifle balances which has a bit to do on how the gun handles on the bags.

Yes! It's all ver confusing until you have some miles on all of it. Really the biggest effect of all of it on accuracy would be not having enough twist, which at 8" or slightly faster you enough. You'll get way more out of LOTS of shooting and learning to keep it in tune than in thinking there is a Holy Grail of the perfect combination of barrel specs.

 

[jelenko]

It's cool to ask experts about things you're not knowledgeable about yourself.

But, I think it's time to move on. There's lots of good info here - especially between Stan's, HasBeen's and HTSmith's input.

I think this is the message:

For sure: Use 103 to 108 grain bullets; freebore .105; twist 1:8 or 1:7.5 [it don't matter which one]; fat, heavy profile;​

Doesn't matter: Groove count - whatever the smith has on hand in a quality barrel; bore diameter - buy one of each and see for yourself.​