Barrel speeding up.

[Milo 2.0]

What's your guys take on a new barrel getting a velocity jump after x number of rounds through it.
1.Does it loose pressure at that time?
2. Does it just (relax) slightly, with pressures holding the same?
3. Or does a pressure spike occur at the same time?

Working with a new Brux 6.5 yesterday, speed jumped at around 40 rds down the tube, historically for me it's usually been 70+. I more interested in pressure theories or facts here.

 

[butchlambert]

What's your guys take on a new barrel getting a velocity jump after x number of rounds through it.
1.Does it loose pressure at that time?
2. Does it just (relax) slightly, with pressures holding the same?
3. Or does a pressure spike occur at the same time?

Working with a new Brux 6.5 yesterday, speed jumped at around 40 rds down the tube, historically for me it's usually been 70+. I more interested in pressure theories or facts here.

Milo, I would question your chrono or a condition change.

 

[Alex Wheeler]

Milo,
Most seem to speed up in the first 100 rounds. I don't know why. Obviously something is causing pressure to go up. It has to be something with the surface finish of the bore.

 

[ShootDots]

I have had new barrels speed up from as low as 20 or so F.P.S. to one, a 6mmBR accelerated about 120f.p.s.>>>which is NOT normal. I have found most speed up about 40 or so f.p.s.

 

[Milo 2.0]

What's your guys take on a new barrel getting a velocity jump after x number of rounds through it.
1.Does it loose pressure at that time?
2. Does it just (relax) slightly, with pressures holding the same?
3. Or does a pressure spike occur at the same time?

Working with a new Brux 6.5 yesterday, speed jumped at around 40 rds down the tube, historically for me it's usually been 70+. I more interested in pressure theories or facts here.

Milo, I would question your chrono or a condition change.

I know for a fact it was neither of those.
It was noticed downrange, and if anything atmosphere wise, it should have dropped off. It was a good jump, 90fps by dope.
Barrel was cleaned, I'll shoot the first few through chrono again, but usually a jump is there to stay?

 

[Alex Wheeler]

What's your guys take on a new barrel getting a velocity jump after x number of rounds through it.
1.Does it loose pressure at that time?
2. Does it just (relax) slightly, with pressures holding the same?
3. Or does a pressure spike occur at the same time?

Working with a new Brux 6.5 yesterday, speed jumped at around 40 rds down the tube, historically for me it's usually been 70+. I more interested in pressure theories or facts here.

Milo, I would question your chrono or a condition change.

I know for a fact it was neither of those.
It was noticed downrange, and if anything atmosphere wise, it should have dropped off. It was a good jump, 90fps by dope.
Barrel was cleaned, I'll shoot the first few through chrono again, but usually a jump is there to stay?

Yes

 

[RDavies]

It is normal for barrels to speed up at the 100-150 round mark, some take a little longer. I would say most of mine have sped up by around 40 fps or so, some more than this. I expect to bump my loads back a little if I get a load sorted before 100 rounds. I am not sure if pressures increased as I only used chronographs, not pressure trace equipment, but I would suspect that if there is a slightly better gas seal causing the velocity increase, there would likely be some sort of pressure increase.