Optimal 6mm BR barrel length

[chino69]

Optimal 6mm BR barrel length ??????????

What would be the best barrel length for a 6mm BR? I've got two Kreiger #18 light varmint barrel blanks. One is a 7 1/2" twist and the other is a 8" twist. They are both 30" long but that is before chambering and crowning. My plans for the 7 1/2" is to have it throated to shoot the 105s, 107s and the 8" to shoot from 75 grn. to 95 grn. bullets. Any suggestions and/or experience would be greatly appreciated.

Lou Baccino

 

[Hornetfan]

I am running a 24 +plus Tennon so depending on how you measure. 24-25inches. Broughton 5c 8twist HV. I have zero complaints.

 

[Dennis Sorensen]

For me it is going to be 25 inches as the present 26 inches is too hard getting into the hard case.

 

[Greg Culpepper]

Lou,

To start, almost 30" is about right if the front of your stock is long enough to support it. You don't need that much but after about 3,000 rounds you can cut three inches off the chamber end and start over. Don't be afraid to shoot 105-07's in an 8 twist. Lots of folks do it in an 8.5". Most 7.5" barrels are selected in anticipation of 115 gn. bullets.

Greg

 

[chino69]

optimal barrel length

Thank you for all the replies.

Greg, you mentioned that 30" is fine if your stock is long enough to support it. These barrels will be mated to a trued Rem. 40X in a HS Precision tactical stock. I wasn't planning on bedding the chamber areas of the barrel, in front of the recoil lug, as I have a Hart 14" that measures larger than the Kreigers. My game plan was to be able to switch the 3 barrels at will. Was this what you were referring to when you said a 30" bbl. would be fine if the stock was long enough? I like the idea of having a 30" barrel that can be re-chambered. I have several excellent shooting barrels that have a second lease on life using this method.

Dennis, do you bed the area in front of the recoil lug on a 25" barrel or is the action, recoil lug, tenon mating surface of sufficient rigidity to prevent barrel droop? Will barrel droop occur regardless and is it a concern? I've seen barrels bedded with and without the chamber area and know there are two schools of thought on this.

Lou Baccino

 

[Greg Culpepper]

Lou,

I don't think you're going to get the balance you want with your stock and a 30" barrel. It takes a long range BR type stock to get the rest out under that long barrel. Sounds like you might be shooting off a bi-pod more often with that tactical type stock. I might try 27" to start and anticipate a cut to 24" when the time is right. Besides, 30" would look goofy on a tactical stock and it is very important to look good, tactically speaking! As far as a bedding pad under the back end of the barrel, don't bother.

Like you, I switch barrels around and no two barrels, let alone three are the exact same diameter. My gunsmith likes an inch of bedding under the barrel in front of a Rem action. I've tried it and it works fine and I've trimmed it back and it still works fine. I did get a tactical rifle to settle down and shoot good for home bedding craftsman by simply removing a wad of bedding around the mag well and 3" up the barrel channel. Its a lot more convenient to just not do it on a switch barrel rifle (but then aren't they all switch barrel rifles?).

Hope this helps,

Greg

 

[Dennis Sorensen]

Thank you for all the replies.

Greg, you mentioned that 30" is fine if your stock is long enough to support it. These barrels will be mated to a trued Rem. 40X in a HS Precision tactical stock. I wasn't planning on bedding the chamber areas of the barrel, in front of the recoil lug, as I have a Hart 14" that measures larger than the Kreigers. My game plan was to be able to switch the 3 barrels at will. Was this what you were referring to when you said a 30" bbl. would be fine if the stock was long enough? I like the idea of having a 30" barrel that can be re-chambered. I have several excellent shooting barrels that have a second lease on life using this method.

Dennis, do you bed the area in front of the recoil lug on a 25" barrel or is the action, recoil lug, tenon mating surface of sufficient rigidity to prevent barrel droop? Will barrel droop occur regardless and is it a concern? I've seen barrels bedded with and without the chamber area and know there are two schools of thought on this.

Lou Baccino

If you are not switching barrels you can bed up to 3 or 4 inches of the barrel if it is straight, not tapered in that area. On tapered barrels I often do an inch... 30 inch barrels have also been hung out there with no bedding and worked okay ...

 

[chino69]

30" looks goofy

Lou,

I don't think you're going to get the balance you want with your stock and a 30" barrel. It takes a long range BR type stock to get the rest out under that long barrel. Sounds like you might be shooting off a bi-pod more often with that tactical type stock. I might try 27" to start and anticipate a cut to 24" when the time is right. Besides, 30" would look goofy on a tactical stock and it is very important to look good, tactically speaking! As far as a bedding pad under the back end of the barrel, don't bother.

Greg,
Now I understand what you meant when you said you need a stock that would accomodate a long barrel. You're right; that 30" tube hanging in a tactical stock looks goofy as hell. I think I'll have at least one of the barrels trimmed to 27" for starters. The other 30" barrel will go into a longer stock. Thank you for your reply.

Lou Baccino

 

[.25shooter]

6BR barrel length

I find barrels longer than about 26 inches diffycult to use. They dont fit well into normal hard cases or even in the back seat of a smaller cars. Besides the gain in velocity is not very much either as Jacky Shmidt has prooven and written about at the 6BR site. So basically I do not understand why so many want all those 30 inch barrels. If some 50-100 fps would be a make or break I would just improve the 6BR case and get them that way. But what do I know, and each his own.

 

[gt40]

For me it is going to be 25 inches as the present 26 inches is too hard getting into the hard case.

Mine has a 26" barrel and fits in this case. About $39 at Dick's Sporting Goods.

gt40

 

[Tony Shankle]

26.75" 6mm barrel in a Tactical Stock.....

 

[Travelor]

Barrel length vs caliber

I got into this discussion with Mr. Larry Racine when he built a 6mmBR for me. He correctly pointed out that barrel lengths vs caliber is a ratio - ie look at the number of "calibers" to the barrel length instead of the actual length. I believe and so does Mr. Racine that the US Navy calculates their barrel lengths in calibers/length rather than actual lengths when calculating a desired barrel length.

Example: A .308 is 1"/.308" or 3.24575 calibers to the inch. A 6mm barrel is 1"/.243" or 4.11523 calibers to the inch. A 30" 308 barrel is 97.3725 calibers long. A 6mm barrel that is the same number of calibers long is 23.66" long.

Mr. Racine reasoned that why would you want a 30" 6mm barrel when that would be equal in calibers to the inch to a 308 barrel being 38" long?

Riddle me this - why are we looking for 6mm barrels longer than 26"-28"?

Just thought I would throw this out for thought.

 

[chino69]

optimal barrel length

I got into this discussion with Mr. Larry Racine when he built a 6mmBR for me. He correctly pointed out that barrel lengths vs caliber is a ratio - ie look at the number of "calibers" to the barrel length instead of the actual length. I believe and so does Mr. Racine that the US Navy calculates their barrel lengths in calibers/length rather than actual lengths when calculating a desired barrel length.

Example: A .308 is 1"/.308" or 3.24575 calibers to the inch. A 6mm barrel is 1"/.243" or 4.11523 calibers to the inch. A 30" 308 barrel is 97.3725 calibers long. A 6mm barrel that is the same number of calibers long is 23.66" long.

Mr. Racine reasoned that why would you want a 30" 6mm barrel when that would be equal in calibers to the inch to a 308 barrel being 38" long?

Riddle me this - why are we looking for 6mm barrels longer than 26"-28"?

Just thought I would throw this out for thought.

Interesting post, thank you for the information. I've never seen this formula before.

Lou Baccino

 

[chino69]

Great looking rig

26.75" 6mm barrel in a Tactical Stock.....

Thanx for the photo.
I just bought one of these stocks along with a HS Precision Tactical stock. What did you paint your Bell & Carlson with? In my opinion, that is one hell of a stock for the money. All the features it has are considered extras or accessories on other stocks.

Lou Baccino

 

[Tony Shankle]

Not painted, it is called Green Spiderweb and is one of their options. It is a heavy stock but comes with all the things I like. The A-5's just suit me.

Plus, I have gotten on this kick of no bedding and the full length aluminum insert in this stock works great for getting my smith to mate it to my reciever.

 

[Greg Culpepper]

Travelor,

I like your ratio analysis, bore v. length. Another way to evaluate barrel length is expansion ratio which will produce different recommendations for the same bore with different case capacities. The concept of optimal includes many possible and frequently competing issues which will change from shooter to shooter and intended use. You wouldn't expect a 7.62x39 ideal barrel length to be the same as one for a 30/378 but they are both 30's (nearly). Neither would you want the same barrel length for a 308 Palma rifle and a 308 woods rifle. Using the old Culpepper wet finger in the wind analog computer establishes the perfect 6mm BR barrel length for 600 yd BR as 26.83". But 30" and 24" work good also. You can cut and re-chamber a 30" a couple of times but you can't make one longer. A few years ago I would not have been eager to put a new chamber and crown on a shot out barrel but I've done it and I'm past those concerns, even for competition.

Greg

 

[Tony Shankle]

I got into this discussion with Mr. Larry Racine when he built a 6mmBR for me. He correctly pointed out that barrel lengths vs caliber is a ratio - ie look at the number of "calibers" to the barrel length instead of the actual length. I believe and so does Mr. Racine that the US Navy calculates their barrel lengths in calibers/length rather than actual lengths when calculating a desired barrel length.

Example: A .308 is 1"/.308" or 3.24575 calibers to the inch. A 6mm barrel is 1"/.243" or 4.11523 calibers to the inch. A 30" 308 barrel is 97.3725 calibers long. A 6mm barrel that is the same number of calibers long is 23.66" long.

Mr. Racine reasoned that why would you want a 30" 6mm barrel when that would be equal in calibers to the inch to a 308 barrel being 38" long?

Riddle me this - why are we looking for 6mm barrels longer than 26"-28"?

Just thought I would throw this out for thought.

Interesting and I am sure the Yodas on this site know better than me but my reasoning is quite different. All of my builds are always long range overbores and I noticed long ago that I get better/more consistant SD's & ES's by picking powders that both give me my target speed while filling my cases as close to 100% or more. Many times while testing powders I have reached that point where it just spits powder out of the muzzle and I don't get any extra velocity...a velocity stall if you will. For the cartridges that I shoot, 26.5to 27.5" seems to be the range that works for me. I have to balance my want/need for a short barrel (not benchrest by the way) with getting a case full of powder and reaching my target velocity. Believe me, I wish they could be 20" and still work for me! Finding this combo is much easier for my big 30's but offers more of a challenge for my 6's.

In short, I don't think a magic formula exist and especially not one that would work for the little BR's through the mid size cases all the way up to the big mags. Now if that formula compensates for load density/case size I would be all ears!

 

[Tony Shankle]

OOOPS! Sorry Greg, I was typing while you made that post or i wouldn't have repeated you (of sorts).

My bad.

 

[Barnard]

Lou,

I don't think you're going to get the balance you want with your stock and a 30" barrel. It takes a long range BR type stock to get the rest out under that long barrel. Sounds like you might be shooting off a bi-pod more often with that tactical type stock. I might try 27" to start and anticipate a cut to 24" when the time is right. Besides, 30" would look goofy on a tactical stock and it is very important to look good, tactically speaking! As far as a bedding pad under the back end of the barrel, don't bother.

Greg,
Now I understand what you meant when you said you need a stock that would accomodate a long barrel. You're right; that 30" tube hanging in a tactical stock looks goofy as hell. I think I'll have at least one of the barrels trimmed to 27" for starters. The other 30" barrel will go into a longer stock. Thank you for your reply.

Lou Baccino

This is my 6 BR
it runs a 1/8 30 inch barrel
tactical stock..GOOFY ???NAHHHH
also took this Hare at 438mtrs

 

[Bill Ohio]

This is my 6 BR
it runs a 1/8 30 inch barrel
tactical stock..GOOFY ???NAHHHH

That setup would look a lot more tactical and less goofy if your prey were Taliban instead of a poor bunny.