Veloxity jump 100ft back and forth

[Sandybar]

All right I need some help. I have a 6mm creedmoore bartlein barrel defiant action. Super tight group shooting gun. It has about 400 round down the pipe. I have a garmin chrono now so I see all my velocity all the time. It's doing something weird cold bore out to around 10 rounds or so it's stable around 3110 fps very low extreme spread. Then it jumps to 3230 from maybe 3 or 4 shots then it's come back down to 3110 node then jumps back up 100 fps then back down again and it's super random. Barrel is not hot and no pressure signs at all.
I'm reloading with hornady 108 eld and 41 grain of h4350. Loaded to Sami spec cole
The rifle is a tack driver and 100 yards even when velocity jumps. So no point of impact shift. Super super problem us at distance at 1600 yards the bullets arw going all over the place because of 100 fps jumps up and down

 

[SOLGardener]

What kind of scale are you using? Is it maybe a scale issue? And how full is the case? Maybe inconsisten primers? And are the case small primer or large? Lapua did small primer in 6.5 creed cases and it was something to do with the flash from large primers.

Bullet weight very consistent? Cases all full length resized? Once fired? Just consider every variable and eliminate all that you can.

If it were me, I'd start with basics of the reloading process and make sure everything was as consistent as can be. If still same results, I'd start trying different primer, different brass, different powder.

 

[BHPSteel]

Being no real expert on this, I did find that a velocity issue I saw in some reloads. I tried first to sort by headstamp, and the problem still hung around, despite hand-metering powder, really stringent case length and bullet consistency.

In the end, it was much improved by me uniforming the flash holes before priming. I suspect that by playing around I might get even better results if I also annealed the brass so I get a more consistent neck tension, but I'm not kitted out for that yet.

Obviously, if you're using quality, new brass you shouldn't need to uniform the flash holes, but it's all I really have at the moment.

 

[Remmy]

If I were to guess I would say you’re on the edge of your node with powder charge even though it’s shooting good.
Might want to go up or down.3 grains of powder and see if it levels out.
If not call Frank at Bartlein and pick his brain
You should be close because I shoot 41.7 grs 4350 with a 140 pill out of a Bartlein barrel and a Brux barrel 6.5 Creedmore

 

[Remmy]

And if you want tight groups at 1600 yds you need to be weighing cases and bullets before loading them and separate
Send some Bergers down that tube, I don’t like Hornady bullets for distance
Velocity isn’t what you need to concentrate on
Extreme spread is what you’re looking for

 

[medium187mph]

All great advice mentioned, don’t overlook anything…

Seems like you’ve got a good load, now you’ve just got to REALLY dial it in and take away all variables

 

[Twitch2120]

Is this all same lot of brass? Mixed headstamps? Fireformed 6.5 creed? Same size primer pockets?

Check neck tension. Depending on dies used and if the brass is annealed it can affect this greatly.

Have you tried factory ammo? Make sure the problem is isolated to your ammo and not your gun.

Last thing I can think of is try different powder and primer lots. I've never heard of a bad powder lots but I have seen bad primers before.

 

[Sandybar]

So I did all I could do and I'm still having the issue. I think if have a bad chamber ans I'm getting pressure coming back onto the case.
So I decided to pull the barrel and bought a proof barrel. I put a bore scope down both the original barrel chamber is junk looking. The new barrel chamber is beautifully machined. I'll shoot the new barrwl Tuesday and let everyone here know if that did the trick. I'm a out 95% sure it's not a reloading issue. But we'll see.

 

[deathbeforehonor]

I never seen you mention what brass? Small rifle or Large rifle primer? Lapua small rifle? They make theirs with smaller flash holes, even if you use Small Rifle Magnum you can occasionally have some weird issues with powder ignition.

How's the PROOF shooting?