6.5 hot barrel shoots lower

[CA_Shooter]

Hi and thanks in advance to anyone with some input on this.

I've noticed a trend with my barrel. And its either my issue or it's coming from my barrel. Not sure which. I have a heavy Krieger, 6.5 creedmoor, 7.5 twist

I've noticed that my barrel shoots lower when it gets hot. It drops about .5 MOA.

I shoot pretty quickly, and the drop happens after about 15 quick shots. For example, I took 15 shots in about 6 minutes.

Its possible it was mirage from the hot barrel messing me up.. Should I change my load?

Any ideas?

 

[RegionRat]

How far are you shooting and are we talking BR, F-class, or sling?

Did you take speed data while running the string?

 

[CA_Shooter]

F-class

Omitting the first shot,, First 14 and remaining shots had the same average velocity and SD. 600 yards

First 14 shots:
1833 avg fps
21 SD

Remaining 15 shots (had some issues zeroing at first)
1831 avg FPS
23 SD

I guess my question is, all things being equal, does a hot barrel whip differently possibly causing a lower shot?

 

[RegionRat]

If a bbl section is very light, it can distort when getting hot.
I’m a little surprised the data isn’t showing a shift that moves your tune.
Rounds getting hot in the chamber can cause them to speed up.

I don’t know what bbl section thickness you are using, but most F-Class barrels are usually thick enough that they don’t have this issue. At least not under a normal circumstance. Sporting guns and things like lever actions can easily demonstrate a drift in POI with heat from rapid strings.

Hammering 15 or 20 rounds downrange quickly will get just about any rig hot, but it sounds like you have some additional troubleshooting to find your issue with a typical F-Class rig.

Six minutes is enough time for conditions to change, but I’m assuming you would know the difference between wind and an abnormal POI shift. Adding in a click before you spill out of a ring may get you by in the interim.

 

[CA_Shooter]

If a bbl section is very light, it can distort when getting hot.
I’m a little surprised the data isn’t showing a shift that moves your tune.
Rounds getting hot in the chamber can cause them to speed up.

I don’t know what bbl section thickness you are using, but most F-Class barrels are usually thick enough that they don’t have this issue. At least not under a normal circumstance. Sporting guns and things like lever actions can easily demonstrate a drift in POI with heat from rapid strings.

Hammering 15 or 20 rounds downrange quickly will get just about any rig hot, but it sounds like you have some additional troubleshooting to find your issue with a typical F-Class rig.

Six minutes is enough time for conditions to change, but I’m assuming you would know the difference between wind and an abnormal POI shift. Adding in a click before you spill out of a ring may get you by in the interim.

This is a thick, heavy barrel. I'm really starting to think its mirage from the barrel. Unless a hotter barrel can change the POI without also changing the FPS, then it's definitely me and not the barrel

 

[RegionRat]

I would never say a bbl couldn’t distort with heating cause I have tested many MG bbls and the steel making and bbl making process has to be done right in order to avoid bad behavior. I am just giving the benefit of the doubt to most modern bbl makers.

On the other hand, if you are not seeing the issue in velocity data as a trend, then it may well be something like a problem with mirage or your scope axis.

My guess is you can manage it since it sounds like a slow trend. That means keeping track of your cadence and watching your progress. Give it a click before it goes out the bottom of the ring.

 

[CA_Shooter]

Linking to this thread, pretty sure it's mirage

Mirage from barrel - POI

I searched prior to posting this and could not get a definitive answer. Also, I have a mirage shade that I'm going to start using. That said, when NOT using a mirage shade, when the barrel gets hot AND using a scope, how does this distort the POI? Do shots go high or low? I've found that my...

forum.accurateshooter.com

 

[4xforfun]

Certainly could be mirage. Very easy to diagnose and fix that problem. Or...it could be uneven stress as the bbl heats up. A BBL can move in ANY direction. If you find it's NOT mirage, then the only fix I can see is sending it off to get a freeze job.

Tod