Late barrel speed up?

[Monday shooter40]

I know the "normal" barrel speed up window is generally around 100-150 rounds for standard sized center fire cartridges, butttt.......... I just had a Dasher barrel finally speed up after 400 rounds. Its been a great shooter and I've had no issues other than it was 40-50 fps slower than its brother barrels. I just shot a match with it last week (third place finish), gave it a good scrubbin, and now its right at the same speeds as my other barrels. Anyone else experience this?

I need to do more documenting, but this barrels cold bore shots suck too. Usually 20fps slow and left of my group. I could probably ignore the left thing, its never more than 1\2" and shooting PRS in the south, the barrel never really cools down during a match day. I don't think it affects any thing during my match, just an observation during load development. Maybe related to the late speed up or an indicator of a less than stellar barrel. I'm certainly no expert.

 

[mgunderson]

Nice job catching the speed up. There is no reason the barrel couldn't speed up late. It would be more common to see a late in life slow down. Nothing in a barrel is perfect and it sounds like something changed.

The left to right could be the barrel has a slight thermal change or the tune is hitting a side to side mode.

Any chance the speed change is related to other common sources like brass, powder lot changes, temperature, powder moisture..... the normal stuff?

 

[Monday shooter40]

Nice job catching the speed up. There is no reason the barrel couldn't speed up late. It would be more common to see a late in life slow down. Nothing in a barrel is perfect and it sounds like something changed.

The left to right could be the barrel has a slight thermal change or the tune is hitting a side to side mode.

Any chance the speed change is related to other common sources like brass, powder lot changes, temperature, powder moisture..... the normal stuff?

I don't think the speed came from other sources. It was slow with other pet loads that I have developed as well.

I run 26" proof barrels. My last two liked 32.0gr varget, in Lapua brass, pushing a 105 hybrid at ~2900fps. Different powder lots would change my speed some, but not more than 10-15 fps. This "slow barrel" was running this load at 2860.

 

[mgunderson]

My opinion is that you are seeing the influence of several factors. Be open to the idea that varget varies more from lot to lot than you have seen so far. Some of the minor factors can work together and create a larger factor.

Never used proof barrels. That is good speed for a 26 inch barrels. Dasher or 6creed? The barrel is clearly different than your others.

I have seen 20 to 40 fps differences in barrel twins that were made and chambered at the same time.

Bore scope show you anything. Carbon ring?

Time will tell with stuff like this. Trying to throw out some ideas for you. It will be interesting to see if it shifts again.

 

[rijndael]

I also saw a late life speedup in a 6Creed, 500-600 rounds IIRC. I thought it was carbon build up so I scrubbed it to bare metal and it was still speedier...

 

[butchlambert]

I've never witnessed this on a custom lapped barrel.

 

[Punkur67]

My dasher just did the same thing. It sped up 40fps around 400 rounds. Quick data correction and it's all good

 

[JFrank]

I've never witnessed this on a custom lapped barrel.

which custom barrels do you shoot ?

 

[butchlambert]

which custom barrels do you shoot ?

Shilen, Bartlein, Kreiger, Rock Creek, and Lilja.

 

[JFrank]

I’ll be darned ‘