Cold bore vs shooter error?

[jippy1]

Is this cold bore? or cold shooter:

1st target is at 100 yards
Hornady’s Match 120gr ammo
New Sako s-20, in 6.5 creedmoor
Vortex razor amg

four shots grouped to .36 moa
However, the flyer to low right was my FIRST shot / coldEST bore shot

Would one ordinarily expect THAT MUCH deviation from a cold bore?
(considering the gun and I can group)

or did I just pull the first shot, and that much error was ME, rather than a cold bore

Second pic are shots 6&7 after a windage adjustment

First group is 1.21 moa, counting the flyer

 

[Noob Sammich]

Next time dry-fire some before making your cold bore shot. That fixes "cold shooter" for me.

 

[Newbie2020]

Cold shooter, not cold bore.

@Frank Green can discuss better than anyone the relative unimportance of cold bore in modern precision rifles

 

[jippy1]

Glad to hear it’s probably me

 

[Frank Green]

Could be the gun?

Cold dirty bore?

Cold clean bore?

Do a chronograph test? If not try it. Cold clean bore and see what the first shot does velocity wise vs the next ones. Repeat the test with a dirty bore. If the velocity of the first round is substantially slower then the next ones...then the barrel wants some sort of fouling in it before it will settle down velocity wise. It's not common but I've seen it. I had one 6mm barrel that from a clean bore....the first round was always a solid 30-40fps slower then the rest. At a 1k yards the first round would always be a mid ring 9 out the bottom. The next round would be in the 10 ring out the bottom and then the gun would hold 1/3moa at a 1k yards after that. I learned not to adjust the scope after that first round or two at that distance. At a 100 yards you could barely see it in the group but stretch the distance out and it would show up.

Box ammo....what is the average SD and ES? I've seen box ammo vary as much as 70 to 100fps in one 5 round string. So lets say the first round was a 100fps slower than the rest....that could easily make the shot go about a .2" low. Now throw in any human error or change in range conditions to the next shot. Also factor in cold clean bore vs cold dirty bore etc...you have a lot of variables.

Watch the video...this is interesting on how light conditions, range conditions, environment etc...can effect you as well. Scope never moved and target never moved. Video was filmed over the course of one day. I'm going to say that's a full 2moa to almost a 3moa shift on the target but the target and scope never moved.



Go into the video settings and slow back the play back speed to the slowest setting and watch it.

Some food for thought for ya....

Later, Frank
Bartlein Barrels

 

[skl1]

Yes, I've had barrels that consistently fired first round out of cold, clean barrel to a different POI. As Frank laid out, sometimes you can see this in Chrono readings. I've also seen it with consistent chrono readings, but on very light contour barrels and on a Remington 742 (semi auto with kind light contour barrel and funny lockup).

 

[Newbie2020]

Good point @Frank Green

I’ve seen the clean bore-dirty bore comparison done and after thorough bore cleaning down to bare metal it takes two fouling shots to re-establish original point of impact.

I want to say the two clean bore shots were 1/2”-3/4” off, then the subsequent rounds were exactly back to the original point of impact vs pre-cleaning

 

[Frank Green]

Good point @Frank Green

I’ve seen the clean bore-dirty bore comparison done and after thorough bore cleaning down to bare metal it takes two fouling shots to re-establish original point of impact.

I want to say the two clean bore shots were 1/2”-3/4” off, then the subsequent rounds were exactly back to the original point of impact vs pre-cleaning

Just watch and see if it repeats....then you know what is going on.

Not every gun/barrel will do it. I can only honestly say I’ve seen it on one barrel.

 

[Jonesing to shoot]

Read this and track the data over your next few range days.

UNDERSTANDING COLD BORE - Ridgeline Defense

In this post we look at the repeatable phenomena of cold bore. We also look at other factors that drive variation shot to shot but are not repeatable.

www.ridgelineshooting.com