Point of impact changes

[kk1939]

Shooting a Ruger American Predator in 6.5 Grendel - informal match at 200 yards. Load is 31gr CFE223 and a 100 gr Hornady ELD match bullet. Load has produced 1 and 3/4 group at 200 yds and 5/8" group at 100yds.

Shooting 200 yds today - sighter and first three targets quite acceptable. Next two targets groups were tight enough but 7" and 9" high respectively. Second time this has happened.

Appreciate any input as to what might be going on. Could rifle heating up be a cause? Match requires 15 shots in 20 minutes.

Thanks

[bamaranger]

Dunno, could be several things. Shifting zero is one of those things drives you nuts. There are members who are far better trouble shooting such things than I am, but I'll offer a few thoughts. If I trusted the scope and the ammo, here's how I'd proceed. If I was suspect of the scope, I'd shoot the rifle with a scope I trusted first. Otherwise.....

I'd get a torque wrench and even up the action bedding screws. I'd check the torque on the little screws that anchor the pic rail to the receiver too. Then I'd see about ring to rail and ring settings as well. No idea what Ruger suggests on the action, the rail and rings don't have to be much 15-30 inch/lbs, but I'd even them up on whatever torque I chose. We're hunting, eliminating binding as the rifle heats. Might help.

My first F-TR match(.308) I experienced sticky bolt lift and a zero change, attributed to the powder I was using, but I'd have to check my log on the rifle to remember what I was using at the time. Some powders are more temp sensitive than others. I'd worked the load up in March with temps in the 40's. At match time it was probably in the 80's, again, I'd have to check my log. Pressure's went up, velocity was likely up, and I shot particularly poorly, even worse than my normal mediocre showings later in my brief F-TR forays. I've no experience with the Grendel, but investigating the powder temp sensitivity would be something I would consider.

Finally, the Predator stock is fairly flexible. There are several Youtube videos about filling the forearm voids with some type of epoxy to stiffen the stock and a DIY bedding job and ensuring a free floated barrel as well. Never done a bedding job and reluctant to say more, but something to consider.

You'll hear from more experienced others i'm sure, but that's my bit.

[44 AMP]

First thing is check and see if your barrel is free floated, and if so, by how much.

And while you're at it, check that all screws are tight. Scope rings, mount, action, all screws.

with everything checked, and changing nothing but tightening loose screws, repeat your shot strings, and see if the POI change happens again, and if its the same as before, or different.

The key to chasing down something like this is to check everything and only make one change at a time. It is also possible the issue is you. See if someone else can get the same results you are getting.
Good luck, let us know how things progress, we might be able to offer advice on things you're not aware of, or have overlooked.

[Rimfire5]

Normally, barrel heating causes my POI to drop, not rise. So I suspect that might not be the cause.

I find that when I focus too much on aiming, I often creep up on my scope a bit and reduce the eye relief. (That is pretty easy to overlook in the heat of competition with time limitations.) That causes my POI to go higher. But I use high power scopes with target reticles. Responding to recoil, also causes me to change my position relative to the eyepiece, so I have to adjust after each shot to keep my groups really tight.

Unfortunately, there is no way to determine you are doing that once you start to move in on a scope.
If you move out, away from the desired eye relief, the POI drops, but you can see a black ring around the image that gets bigger as you move backwards. That gives you a warning sign, but when moving closer, you get no such warning sign.
I found out years ago that 1/8 of an inch can cause as much as 1/4 an in change in POI at 100 yards if you move closer. A 7-inch change is really severe, so there may be more than one cause.

If you are using open sights in competition, movement relative to the sights might also have the same effect. It is very easy to adjust your position relative to the front sight and change the angle of aiming. That would also change the POI.

[stagpanther]

I've seen dramatic changes in POI when shooting longer distances with 22lr when changing the angle of the rifle to target; which I believe might change the distance/time of flight of bullet. This happens when I raise or lower the rifle when shooting at a target which is higher or lower than the one I just shot and the elevation was right on POA. Might also be even a slight change in alignment of the eye to ocular lens contributes to the problem (?).

[tangolima]

The rifle has bedding block and free float barrel. Heat shouldn't be much a problem. Were you shooting off bipod or front rest? Any rear bag? Prone or bench top?

2" (7" to 9") shift at 200yd is 1moa. Noticeable but not terrible.

-TL

Sent from my SM-N960U using Tapatalk

[FrankenMauser]

My immediate impression of the original post is that it is an eye alignment issue.
Check your eyebox.

[44 AMP]

Next two targets groups were tight enough but 7" and 9" high respectively.

To be clear, for no apparent reason, your group moved 7 inches high above your point of aim, and the next group was 2" above that??

is that right?

[Shadow9mm]

Check torque on action screws/bolts. Action might be shifting in the stock.

Check torque on scope base and rings. Might be loose.

Did you dial your scope for elevation/windage for 200yds? Could be your scope is not tracking properly?

Could your turrets have been bumped/moved during transport?

Does your optic have a paralax adjustment?