6mm barrel inside Dimension

[BenPerfected]

Most of my barrels have been .237 but I recently bought (2) Brux .236 barrels. Just shot 50 rounds today with a new .236 barrel & it showed more copper on the 1st three patches vs. the .237. This makes sense, but curious about others experience on the accuracy on these two different diameter 6mm barrels.
Ben

 

[gunsandgunsmithing]

Most of my barrels have been .237 but I recently bought (2) Brux .236 barrels. Just shot 50 rounds today with a new .236 barrel & it showed more copper on the 1st three patches vs. the .237. This makes sense, but curious about others experience on the accuracy on these two different diameter 6mm barrels.
Ben

I've done this several times with the same results but,
I just took a .236 off that shot great before laying down, and replaced it with a .237. I can't tell much difference but if anything, I think this .237 might be a tad better in this case. What I'm really saying is that a good barrel is a good barrel, as I can hardly discern a difference, if there even is one. The only difference in loads between the two barrels seems to be in seating depth. The new one seems to like a little shorter oal, which might be a bit counter intuitive given the larger land diameter. Shoot it and see. If it's a good barrel, I doubt you'll be disappointed

 

[BenPerfected]

Thanks for the response Mike. Note that all my barrels are threaded for your tuner. Based on today’s 50 test rounds @ 500 yds, it was hard to compare the group results to a fully tuned barrel. The only tuning done today was making small adjustments with your tuner. Haven’t even started with seating depth. This barrel was brushed & cleaned at about 20 rounds. I also didn’t use any flags testing today because between 7:30 & 9 am I can usually test @ 5 MPH +/- . Much after that, reading the wind at 15+mph even with wind flags is still an opportunity for me.
Something that has worked for me when shooting a barrel that starts to lose it’s edge, is to clean it very aggressively with a bronze brush. I was surprised on how much crud was removed. I am starting to believe the following that says you are not going to hurt a rifle barrel with a bronze brush.
Ben

 

[gunsandgunsmithing]

Thanks for the response Mike. Note that all my barrels are threaded for your tuner. Based on today’s 50 test rounds @ 500 yds, it was hard to compare the group results to a fully tuned barrel. The only tuning done today was making small adjustments with your tuner. Haven’t even started with seating depth. This barrel was brushed & cleaned at about 20 rounds. I also didn’t use any flags testing today because between 7:30 & 9 am I can usually test @ 5 MPH +/- . Much after that, reading the wind at 15+mph even with wind flags is still an opportunity for me.
Something that has worked for me when shooting a barrel that starts to lose it’s edge, is to clean it very aggressively with a bronze brush. I was surprised on how much crud was removed. I am starting to believe the following that says you are not going to hurt a rifle barrel with a bronze brush.
Ben

Thanks Ben!

I'm in that camp...that a CLEAN bronze brush will never hurt a barrel.

 

[ShootDots]

I have a theory BUT it is only a theory. I believe that very short bearing surface bullets, like 62-68gr 6mm pills, primarily used for S/R Benchrest comp., are served better by a "conventional" rifled .236 bore. A long bearing surface projectile, i.e. 103-115gr L-O-N-G range bullet, will be better served by "canted or 5 R rifled" .237 barrels. WHY? In short, "friction" causes LOTS of heat. Bullets with literally twice the bearing surface, going down NOT a 20" barrel but 30+" barrels will create A LOT more heat. This can and does affect the integrity of the bullets and in turn accuracy. I have seen 1-7 twist .22 cal 90gr pills blow up because of "conventional" rifling out of a .223 for F-T/R. There are stories about 6mm and 6.5mm bullets blowing up for the same reason. ADD a 0.001 TIGHTER bore on "long-for-caliber" bullets, only adds to the equation.

 

[WayneShaw]

What I'm really saying is that a good barrel is a good barrel

This.

 

[500Stroker]

Most of my barrels have been .237 but I recently bought (2) Brux .236 barrels. Just shot 50 rounds today with a new .236 barrel & it showed more copper on the 1st three patches vs. the .237. This makes sense, but curious about others experience on the accuracy on these two different diameter 6mm barrels.
Ben

I shoot Brux 6mm .236 barrels.
I do not question their accuracy.

 

[jbhotrod]

I have a theory BUT it is only a theory. I believe that very short bearing surface bullets, like 62-68gr 6mm pills, primarily used for S/R Benchrest comp., are served better by a "conventional" rifled .236 bore. A long bearing surface projectile, i.e. 103-115gr L-O-N-G range bullet, will be better served by "canted or 5 R rifled" .237 barrels. WHY? In short, "friction" causes LOTS of heat. Bullets with literally twice the bearing surface, going down NOT a 20" barrel but 30+" barrels will create A LOT more heat. This can and does affect the integrity of the bullets and in turn accuracy. I have seen 1-7 twist .22 cal 90gr pills blow up because of "conventional" rifling out of a .223 for F-T/R. There are stories about 6mm and 6.5mm bullets blowing up for the same reason. ADD a 0.001 TIGHTER bore on "long-for-caliber" bullets, only adds to the equation.

Interesting. I see where you're going and it would make some sense. However, I think bore cross section is what would contributes most to friction, no? Regardless of 5R, 4, or 6 groove. IIRC thats the gist of how Mr Frank Green explained it anyhow. I could be wrong though, and both larger bore cross section *along with* canted lands contribute to keeping long heavy bullets together at high MV's in the fast twist barrels required...?

I'd also imagine gain twist could help, especially when combined with a bit larger bore cross section & 5R/canted lands... and ESPECIALLY ultimately experimenting & finding the optimal combo!

 

[ShootDots]

Interesting. I see where you're going and it would make some sense. However, I think bore cross section is what would contributes most to friction, no? Regardless of 5R, 4, or 6 groove. IIRC thats the gist of how Mr Frank Green explained it anyhow. I could be wrong though, and both larger bore cross section *along with* canted lands contribute to keeping long heavy bullets together at high MV's in the fast twist barrels required...?

I'd also imagine gain twist could help, especially when combined with a bit larger bore cross section & 5R/canted lands... and ESPECIALLY ultimately experimenting & finding the optimal combo!

I believe that gain twist would help. However, I have zero experience with gain twist barrels. Remember I am just working on a theory based on some recent experiences. I am not a barrel maker, neither am I a ballistician. I am trying to minimize mistakes that I have recently made in regards to my "theory".. I have blown up bullets that were not travelling all that fast, I have seen various bullets with long-for-caliber bearing surfaces blow up and T-Rust me, blow-ups do nothing for scores! LOL!! Besides that, the cost of barrel replacement, spent components etc.. only adds to the cost. I am just trying to figure out how to maximize potential with a minimum of "mistakes"..