6.5 GAP Barrel Length?

[MagnumManiac]

Hi all,
Have ordered my 6.5 Bartlein blank 5R 1:8" twist 31" finished length.
Looking to see what you guys/gals recommend on length?
This is primarily a comp gun, but may also use it for some hunting.
So, should I stay at 31" or something shorter?

Cheers.

 

[Kimber7man]

I wouldn't know. I just sent my 24" 6.5Gap4S back to GAP to chop it to 20"...

 

[Mikecr]

I would go at least 28" to keep muzzle pressure reasonable.

 

[bill123]

I would go at least 28" to keep muzzle pressure reasonable.

Can u explain that?

 

[MagnumManiac]

Thanks. Was thinking 30", then I can set back and rechamber when needed.
I'm not going my usual route with 3 different barrels in differing lengths, just the one.
I think the throat will last a little longer than my 264WM barrels do. Hoping to be less than .018" per 300 rounds or so.
I really want to try one or two of the Vhit powders in this, any recommendations?

Cheers.

 

[DJ Fergus]

Hi all,
Have ordered my 6.5 Bartlein blank 5R 1:8" twist 31" finished length.
Looking to see what you guys/gals recommend on length?
This is primarily a comp gun, but may also use it for some hunting.
So, should I stay at 31" or something shorter?

Cheers.

My 6.5 gap has a 27" but only because i got a deal on the barrel. Otherwise I would have went 28". I like long barrels. For what you are going to use it for, I see nothing wrong with a 30" barrel.

 

[Mikecr]

Can u explain that?

Muzzle pressure is the big ole fireball of powder burning OUTSIDE the bore, slapping the back of releasing bullets, challenging stabilities..
MY muzzle pressure limit is ~8Kpsi as seen through QuickLoad. It's 8Kpsi wasted.
Beyond that, it's time to go to a smaller capacity cartridge/faster powder, for the same results and potentially saving barrel life.

This is about early choices. For example: I want to drive 26cal 140gr bullets to mid node velocities of 2950-3000. I could choose the overbore 6.5x284, or 260AI. I would choose the 260AI, with 26-28" barrel. It can meet the goal with WAY less powder, and WAY lower muzzle pressure than a 6.5x284. When you consider real accuracy, which is what you can manage in the long run, the choice here is easy.

GAP builds accurate guns. Any choice there should be good enough.
George went even more overbore to take advantage of cool H1000 powder, for comfortable upper node AND good enough barrel life(as good as 6.5x284). Through barrel length you could choose lower node ~2800fps, all the way to upper node ~3150fps.
Lower nodes are generally more accurate, but you're giving up a huge velocity potential (nothing is free).
Personally, I like mid-nodes, 28" barrel makes it a breeze.

 

[DJ Fergus]

Muzzle pressure is the big ole fireball of powder burning OUTSIDE the bore, slapping the back of releasing bullets, challenging stabilities..
MY muzzle pressure limit is ~8Kpsi as seen through QuickLoad. It's 8Kpsi wasted.
Beyond that, it's time to go to a smaller capacity cartridge/faster powder, for the same results and potentially saving barrel life.

This is about early choices. For example: I want to drive 26cal 140gr bullets to mid node velocities of 2950-3000. I could choose the overbore 6.5x284, or 260AI. I would choose the 260AI, with 26-28" barrel. It can meet the goal with WAY less powder, and WAY lower muzzle pressure than a 6.5x284. When you consider real accuracy, which is what you can manage in the long run, the choice here is easy.

GAP builds accurate guns. Any choice there should be good enough.
George went even more overbore to take advantage of cool H1000 powder, for comfortable upper node AND good enough barrel life(as good as 6.5x284). Through barrel length you could choose lower node ~2800fps, all the way to upper node ~3150fps.
Lower nodes are generally more accurate, but you're giving up a huge velocity potential (nothing is free).
Personally, I like mid-nodes, 28" barrel makes it a breeze.

I never really understood why some folks want a super overbore cartridge and run it in a 24" or less barrel. I guess it's because they don't understand either, LOL.

 

[MagnumManiac]

Thanks for the info. My shortest comp barrel is 28", but I do mess about with barrels that are 26" for informal craps & giggles...just like the 7STW in the works at the moment. The barrel was the donor rifle barrel in 7RM on a Sendero II, thought it would be fun and a learning curve as I have NEVER been a 7 guy.

Cheers.

 

[Mikecr]

I'm sure that if short barrels were always better, then by now ALL guns would be short.

There is another issue with barrels too short -> pressure problems.
A secondary ignition at the muzzle can actually cause higher than the primary pressure peak near the chamber.
This can lead to pressuring out earlier in load development.
Note sample trace #3 & #5 here: https://www.shootingsoftware.com/pressure.htm

I wouldn't want to smack boat tails with that, while having any less than a stellar crown.

 

[jrock]

I did 28" on my hunting rifle and its plenty long. I am getting about 3150 to 3200 fps easy. I think 26" would have been adequate for a hunting rifle.

 

[grouse]

There is a member on snipers hide that is getting 2825 with 147 grain out of a 16" barrel

 

[Mikecr]

And Jrock gets another 400fps with a pound heavier gun. If velocity really was all that mattered -Jrock wins bigly.
If you dug into it, looked across a gamut of ballistic attributes, you'd see he wins in a lot of other ways too.

 

[jrock]

That's with 140 grain Bergers. Its down to 3050 with the Berger 156 both using H1000. My chorony could be lying, got to love that 1% error. I haven't conducted any LR drop data on either to verify. Still doing load development.