"tight bore" question

[millbastard]

Hi everybody. Hopefully someone out there might have some insight. Does a "tight bore" behave like a longer barrel; an 18" seem like a 24"?
To me it would make sense the increased friction of the "tight bore" would yield higher velocities especially with the heavier weights.
Also would Bartlien's "T" rifling handle throat erosion better with higher velocity since the twist can start at a longer rate than normal?

 

[6brshooter]

Tight bore won't make a barrel seem longer. The reason u see .236&.237" bore dimensions on the 6 mm barrels is because that is the most popular caliber for BR. Krieger explained to me that if u plan to shoot Sierra, Berger hornady etc. bullets then go with the tight bore. If u are planning to shoot custom made br bullets, which typically have a ring or bulge, then the .237" is better.

 

[6brshooter]

Case in point, i have a remage with a 24" bull criterion in 243 1-8 twist. 42.0 gr of h4350 and a 106 smk get me 3170. I have a tight bore Krieger on a tikka that is 25.5" 243 1-8 twist. It needs 42.5 gr of h4350 to get a 107 smk to 3125. 1.5" longer half grain more of powder, and tight bore. Still 45 fps slower.

 

[Edds]

There is a thread on here where Frank from Bartlein said generally tighter is slower and looser is faster. The way I understood his comments, you need to consider the total cross section area.

 

[Frank Green]

Tight bore won't make a barrel seem longer. The reason u see .236&.237" bore dimensions on the 6 mm barrels is because that is the most popular caliber for BR. Krieger explained to me that if u plan to shoot Sierra, Berger hornady etc. bullets then go with the tight bore. If u are planning to shoot custom made br bullets, which typically have a ring or bulge, then the .237" is better.

Not necessarily. I use to shoot .236 bore barrels when I use to work at Krieger but I don't anymore. The tighter bore can cause bullet failure as well. I experienced this first hand. You get a batch of bullets with a thinner jacket or a problem with the cores etc...the tighter bore the lands can cut thru the bullets jacket and or create a stress point on the jacket and this can lead to bullet failure. I had this happen with Berger 105 VLD's and a tight bore .236 Krieger barrel I had on one of my guns when I was there. I figured the barrel was at the end of it's life and the bore was getting rougher and this was the cause of the problem. So I pulled the barrel after I had some bullets fail that match at a 1k yards. I put a new barrel on the gun again in .236 bore and again I had some bullets fail to make it to the target at a 1k yards. I went back to Sierra's 107's and no failures. I feel the bullets out of that particular lot themselves were the cause of the failure problem and not the barrels but I don't feel the .236 bore was helping anything.

After that problem with the Berger's I purchased a different lot of Berger's and no problems.

I only run .237 bore barrels now on my guns. I shoot mostly Berger's. Some Amax's and Sierra's (right now what ever I can get my hands on for the most part). There is no difference in accuracy or barrel life between the two bore sizes.

Yes the short range bench guys with bullets with bullets that are running slightly bigger than .243" diameter are running almost exclusively the .237" bore size. Some have found that the .237 bores are more consistent shooters with the fatter bullet. Again these are short range bench shooters. I don't see a difference in the real world again between the different bore sizes when it comes to accuracy and or barrel life.

We are tooled for both .236 and .237 bore barrels. The .237 bore barrels are about 95% of our orders.

Later, Frank
Bartlein Barrels

 

[K_4c]

Thanks for the clarification Frank.

 

[Frank Green]

There is a thread on here where Frank from Bartlein said generally tighter is slower and looser is faster. The way I understood his comments, you need to consider the total cross section area.

Yep!

Keep in mind guys when someone says they are running a tighter bore ask them to be specific. Alot of guys use the term bore generically for the bore of the barrel. Ask them.....

Tight bore you mean the tops of the lands which is actually the bore of the barrel?

or

Do you mean the groove size?

Groove size will have a bigger impact than the bore (tops of the lands) will.

Also a difference of a 100fps from one barrel to the next could just be the individuality of the barrel itself.

Also ask this question. Same chamber reamer used from one barrel to the next? Different reamer with a different throat spec. can cause variances as well that will effect pressure and velocity.

How much wear does the barrel have in them?

Later, Frank
Bartlein Barrels

 

[millbastard]

Thanks guys. Just wondering 'cause I was planning on getting a BOP Recon and it has a "tight bore" 18" barrel in .308.
What about the "T" rifling though or should I save that for another thread?

 

[Frank Green]

Thanks guys. Just wondering 'cause I was planning on getting a BOP Recon and it has a "tight bore" 18" barrel in .308.
What about the "T" rifling though or should I save that for another thread?

The .299 bore .30cal. barrels are the most popular we do. .30cal. is more forgiving than the 6mm caliber. The lands of the barrel do the driving on the bullets. If the tight bore should help anything I would lean towards it helping barrel life. Keep in mind there are a lot of variables that contribute to barrel life.

Do the "T" style gain twist for another thread. Do some searches as it's been talked about before.

Later, Frank
Bartlein Barrels