Question about barrel groove diameter

[40X Guy]

i am looking at a Bartlein 6MM 8 twist 5R barrel, i have my choice of a .236 or a .237. Usually I shoot Sierra's and Lapua Scenars, which one should I be looking at and why? Thanks in advance.

Frank

 

[WayneShaw]

You'll never realize a difference. A good barrel is a good barrel. Number of lands, bore diameter, a good barrel will shoot.

 

[40X Guy]

I can agree with that Wayne, and I have heard or read nothing bad at all about Bartlein barrels. Just talked to my smith and his view is that the .236 barrel is good for short range BR and keeping velocities higher. For LR BR his view is that the less deformation of bullet the better at long range so he's saying go with the .237 groove diameter. I am just trying to weigh all the pros and cons and hear from experience. And this would be for 600-1000 yard shooting.

Frank

 

[BoydAllen]

You probably already know this, but the numbers discussed in earlier posts are not groove diameters. They are land diameters. The standard groove diameter of a 6mm barrel is .243.

 

[40X Guy]

Boyd, thanks for the correction, I got them mixed up.

Frank

 

[fullersson]

Lapua's tend to like a tighter bore because they are skinner. Figure out which bullet you are going to shoot and if that is the Lapua's go with the tighter bore. If you are going to use some other bullet go with the larger bore. A small bore with the bigger bullets will promote bullet failure especially if you are already close to the line. Good luck, Brian.

 

[40X Guy]

Thanks everyone for the replys, I ordered the .237 land diameter as I have been leaning towards Sierra's and A-Max on this next build.

Frank

 

[FroggyOne2]

Lapua's tend to like a tighter bore because they are skinner.

Funny, I had the opposite effect the Lapua bullets in 308, the lapua's greated more pressure in my rifle than the Sierras did. It was a tight bore palma barrel.

 

[fullersson]

"The Lapua 105gr Scenar is a very uniform bullet and ultra-accurate, but the max diameter is 0.24285, compared to 0.2433+ for some other brands. Accordingly the Scenars may prefer a tighter bore. They shot superbly in this editor's PacNor 8-twist and a .236-land Krieger tested by Jackie Schmidt."

http://www.6mmbr.com/6mmbr.html

The above quote came from the above article. The question that was originally posted concerned 6mm bore diameter. I don't know anything about .308 and couldn't expalin why the Lapua's created more pressure than the Sierra's. Good shooting, Brian.

 

[JDMock]

I have had better success with a .236 bore in the Bartlein 8.25 to 7.75 Gain Twist. It is chambered for the 6mm Dasher and I use 105 Berger (Hunting) VLD's. I push these with 8208 XBR powder. In the short range 6 PPC, I use a 14 twist with .237 bore....just the opposite of the above suggestion. Maybe that's my problem :'(. James

 

[Laurie]

Funny, I had the opposite effect the Lapua bullets in 308, the lapua's greated more pressure in my rifle than the Sierras did. It was a tight bore palma barrel. [FroggyOne2]

Apart from there not necessarily being any similarity in this respect between Lapua 6mm and .30 Scenars, many more factors than the bullet dia. to groove dia. match alone influence pressure. Key factors are bearing surface lengths, the .30 155gn Scenar for instance having a 0.472" length compared to 0.230" for the new model Sierra Palma, likewise the 155.5gn Berger. Then there is jacket thickness and hardness, gilding metal composition, lead-antimony core make-up and hardness etc.

Laurie,
York, England