Going to 26 inch barrel from 24, slower powder?

[Jake the dog]

I'm currently using H4350 in a 24 inch 6.5CM. I'm getting a new barrel next week, and am wondering if I should be looking at a slightly slower powder to get the most out of the longer barrel. It doesn't seem like a lot of difference, but it's new to me, and I know there is a great deal of experience on here.

 

[Supersubes]

Nope

 

[Steel head]

Nope

X2

 

[Greg Langelius *]

I've been shooting a 260 at 28" since about 2003, and I'm still using H-4350 with 140-143gr bullets. I tested H-4831 way back in a 24" barrel and found better accuracy but less velocity.

These days, velocity is less crucial due to a higher shooting altitude(4350-ish) and the 28" barrel, and I may return to testing with H-4831SC. There are still a number of projects in the queue so this may get done in 2020, may not. Main goal will be getting accuracy out of the 143gr ELD-X.

My key strategy to using the longer barrel was not so much to get greater velocity, but to maintain the same/similar velocity with less heat/pressure, perhaps prolonging throat life.

Considering that the barrel is 15-16y/o and still going pretty danged strong, that may be working. It may also be due to less LR shooting on my part, estimating 1600-1800rd downrange.

Greg

 

[spife7980]

I'm currently using H4350 in a 24 inch 6.5CM. I'm getting a new barrel next week, and am wondering if I should be looking at a slightly slower powder to get the most out of the longer barrel. It doesn't seem like a lot of difference, but it's new to me, and I know there is a great deal of experience on here.

No, burn rate choice is more a funciton of bullet weight and rate of volume change behind the bullet (chamber volume + bore volume growing over time).

Most of the speed is gained in the first few inches, a few inches of longer barrel wont suddenly make a less optimal powder selection more optimal than a better powder selection in the first place. Choose the best powder no matter the barrel length.

3,800 fps at the end of a looooooong ass 48" barrel.

In the first 10" the bullet is going 2,700 which is 70% of its total speed if one were to run a 48" barrel.

At 25" ----which is 15 additional inches (aka a barrel 2.5x as long, aka a 150% increase in barrel length)---- and the bullet is going 3,500 or 92% of the total possible speed... but thats only an additional 30% in the velocity gained with a barrel 150% longer.

 

[Jake the dog]

Thanks to all. I'm really happy to hear this, I just opened an 8 lb jug of 4350.