Down to one box of Match & a storm is moving in . . . So...I had me an idea?
https://i.imgur.com/sBt6Xyn.jpg
While I have the time before the storm...I thought I might clean that CZ's barrel with a wet mop & dry it and clean that chamber and get ahead of the curve a little. Next week that order of Eley Match arrives at my FFL, so...why not get the barrel seasoned up and ready to fly when the ammo arrives?
I thought too, that it'd be a good time to watch the first 50 shots as the barrel 'seasons in' from the wet mopped barrel and just see what I might see?
I used the Poppa's Rest so I could eliminate as much as I can, all the err I might put into this observation...that rest is a tall one, I had to add sand bags to my stool & my arm rest...
https://i.imgur.com/X7hPeqd.jpg
Anyway...here's what I got...
https://i.imgur.com/RVppTnz.jpg
After packing everything in before the rain caught me on the bench, I sat in the shop & measured up the groups.
As usual...I'll crack a cold beer and just study what happened, study how the groups started out tight on the warmer spot (that's unusual), then started meandering around the POA.
The POI is adjusted to hit next to the vertical on the left and above the horizontal...just almost touching those lines but intentionally 'not obliterating' the cross in the 1" circle. When that blows out it gets a little more difficult to align my cross-hairs in the scope with the lines on the target.
I have been thinking a lot about how the barrel oscillates when the shot is fired.
Does it wiggle around in a circle and settle back to it's static position before the shot was fired...or...does it wiggle around in a figure 8? That's been something I've wondered about when I was doing the 'tuner testing' with the 2 shot groups. This I am not sure of & haven't read or seen anything definitive about barrel oscillations. For as many opinions I have read or watched on a video, there seems to be a different account of what happens. I have seen the ultra slo-motion of an AR barrel filmed from the side and could see it whip up and down but it does not show any side to side compound reaction. That leaves me wondering about it.
Anyway, I thought...if you drew a circle around the main body of the group, encompassing where the majority of the rounds hit & taking into consideration where several rounds share the same hole...you might be able to see where the barrel was pointing in a general sense for that group.
I think the groups meander around as the barrel heats from the sunlight directly on the steel & from the heat generated from within the barrel. I think this ongoing heating changes the way the barrel reacts to the groups as this heat builds up to where it tends to maintain some kind of equilibrium?
Yah...I know, that's a mouth full to consider but bear me out...
I drew circles around where I think the aggregate/average centers of each group is in each spot. I thought that smaller circle might show me where that bull barrel might be point for those 5 shots. Then looking at the progression of the 10, 5-shot spots I shot, it might help to explain this meandering of the groups?
Here's what I got...
https://i.imgur.com/fUQi16t.jpg
Notice how the last 5 shot groups on the right side tend to show the barrel pointing more or less in conjunction with where the POI has been previously adjusted. I am thinking that the barrel had started to maintain some semblance of 'heat equilibrium' for the conditions I had today. It was 50ºƒ this morning and because of the cloud cover I had no effect of heating from the direct sunlight, just the interior heating from the rounds fired.
I still can't be sure of the barrels reactions to the harmonics, whether it moves around in a circle, a vertical oval or a figure 8 but I am certain it is moving and that the amount of heat in the barrel determines where the barrel is pointing when that projectile leaves the muzzle.
Now I am not saying..."this is what is happening" by any means...just posturing a few thoughts.
I am definitely interested in what you fellas think, if you actually think about barrel harmonics and have some theories of your own...I'm not trying to convince anyone of anything, just spitballing from what test we have seen thus far in this thread and the thread about the 'peep & globe' on the Sav. MKII.