Decreasing Velocity - 6 cm

[estes640]

I’ve got a 6cm that has around 60rds on it. Today I took it out to the range and had an experience where the velocity slowly dropped from 2999 to 2888 with the same ammo, not lot change. I was running it suppressed. Any ideas why the velocity would slow down ofver the course of a range session?

 

[Evlshnngns]

What chronograph?

 

[estes640]

What chronograph?

garmin Xero

 

[estes640]

Should add some more context. Shooting factory hornady 108 eld match ammo

Just looking for some ideas to chase down. Major copper fouling, etc?

 

[ShtrRdy]

Was it cold out to where your ammo started out warm and cooled off as you were shooting?

 

[estes640]

Was it cold out to where your ammo started out warm and cooled off as you were shooting?

Nope. Was thinking that originally as well, but all ammo was shot within an hour and from what I remember the temp didn’t change much. Maybe shade vs sunny? I fell like I’m grasping at straws

 

[Walt Krafft]

I heard that it takes 2,3 sometimes 400 rounds for the 6 Creedmore velocities to settle down in a barrel. No one seemed to know why.

 

[bobby1028]

110fps, should have shown some poi shift to match the chrono...any change in impacts ?

 

[Bill Norris]

I’ve got a 6cm that has around 60rds on it. Today I took it out to the range and had an experience where the velocity slowly dropped from 2999 to 2888 with the same ammo, not lot change. I was running it suppressed. Any ideas why the velocity would slow down ofver the course of a range session?

If the barrel was picking up copper which is likely with new barrels that could be the answer.

 

[Fast14riot]

Did you start with a clean bore?