Cold bore zero versus (very) Hot bore zero “test”

[donrleonard]

Go test it. Shoot a 10 round string and number every shot. Let your barrel cool between each shot. Then repeat it without cooling. It’ll give you a pretty good idea of how, if at all, barrel heat is affecting your group.

FWIW I’ve had two lightweight rifles with pencil barrels that will rattle out a 10 round group with no ill effects. One is a 6.5 and the other was a .280 Remington.

Great idea. Challenge accepted!

 

[wind gypsy]

It's a great point, and one that I need to drill on for hunting--staying in the scope, spotting impacts, and being prepared to take follow-up shots.

The thing that puzzles me is just how consistent it is. Two tight shots low, two high, and a random 5th shot inside of a 2" cone.

Do they progress in the same direction?

Other shooting gurus, like Joseph von Benedikt and Cliff Gray, do commonly see accuracy open up after as few as two or as many as 5-7 shots. Given their vast experience, I can't help but wonder if there isn't some systematic variance in the 1-10 shot range inside these 30-shot strings that Form reported here.

Not familiar with the Cliff Gray fella. I’m guessing they get a bunch of production guns that wear barrels that are not adequately stress relieved, carbon barrels that walk, etc so I’m sure it happens to a degree and I’m sure sometimes it’s not heat that is causing the issue as well but that’s what everyone is conditioned to assume.

 

[Macintosh]

The thing that puzzles me is just how consistent it is. Two tight shots low, two high, and a random 5th shot inside of a 2" cone.

I am a little skeptical if its legit to call this “consistent”. If you did 10 separate 5-shot groups, all staying in the gun for the full 5-shots, and every group progressively “moved” the same way (ie 2 on poa, 2 higher, then a third even higher) Id say the stringing was consistent. But I see in the 3 examples you posted the 5th shot in one case is high, and in the other case it’s 180-degrees in the other direction, and in one case a tight pair is more offset horizontally than it is vertically. I may have missed it, but how many 5-shot groups had the consistency you are referring to?

It just seems odd that if its walking UP as it heats as you indicated, that the 5th shot would be up in one case, and then below the first shots in the other case (all the stringing Ive ever seen with older rifle or those not floated, etc stays in one direction), and that the pair in the one case would be offset horizontally. Im no expert but regardless of whether its heat or something else that does not point to a consistent shift to me.

 

[nephewjephew]

The thing that puzzles me is just how consistent it is. Two tight shots low, two high, and a random 5th shot inside of a 2" cone.

I've chased my tail on a few guns like this. Not getting good (or confusing) 3 or 5 rd groups, chasing zero etc,etc. Shoot a 30rd group, I bet they all fall in the cone of the rifle. Once I started down this road I have had no problems (along with a scope that works). Its a great way to set a base line for the rifle and gives unbelievable confidence in the rifle system. More data to start with the better.