POI shift between range trips.

[jsthntn247]

Not being bedded is the #1 culprit in most cases. However this causes big poi changes 2-3" with wood stocks. I think what you are seeing is lighting and temp differences. When shooting fclass matches in sunny conditions if a cloud would come over it would immediately shift poi by 4" at 600 yards, the sun would come back out and poi would go back to the same spot. I can sight in at 100 right before dark then shoot the next day at lunch and have a 1" poi shift in zero. Frustrating but normal.

 

[Gunpowder]

Thermal compression is real—as the sun sets and the cooler (denser) air starts to settle toward the ground, the air creates a falsely compressed picture of the target. This results in shots landing off the vertical POA since the target itself hasn't actually compressed.

That is really interesting, I've never read an actual reason for it, just that it can happen. Thanks

 

[JustMe2]

Thermal compression is real—as the sun sets and the cooler (denser) air starts to settle toward the ground, the air creates a falsely compressed picture of the target. This results in shots landing off the vertical POA since the target itself hasn't actually compressed.

He said, "NEVER up and down."
IMHO, it is most likely lighting or shooting form changes. You may be putting more or less cheek pressure, shoulder pressure, trigger hand grip pressure/strangle hold, forehand position is on forend or is on rear bag, not same square behind stock, etc.

 

[new2mud]

He said, "NEVER up and down."
IMHO, it is most likely lighting or shooting form changes. You may be putting more or less cheek pressure, shoulder pressure, trigger hand grip pressure/strangle hold, forehand position is on forend or is on rear bag, not same square behind stock, etc.

Not sure how much of the actual thread you read, vs. skimming and jumping in.

I addressed that in my follow up post Re: applicability to OP.

However, another member asked about the rise in POI he experiences at dusk. Yes, our threads often contain ancillary sub-topics, which I have learned a ton from personally.

 

[emp1953]

So this has been bugging me, and I'm curious if its common/normal or correctable. I've been consistently noticing left/right POI shifts randomly throughout range trips. NEVER up and down. Just left/right. Sometimes 1/2", sometimes 1", sometimes nothing at all. I never noticed this at all last year, but after 7 backcountry hunts, I'm noticing it, and wondering if I did something while hunting/packing meat. Been doing a lot of tinkering/load development now that it's the off season and making tons of trips to the range. Even shooting the same load as the prior trip, sometimes I will see a shift. The gun is a custom 28 nosler and a tack driver. Consistent 1/2 MOA with several loads. What could be causing this? Is it me? Is it normal? Is there something minute with the rifle that could cause this that I should look into?

I shoot from the same position every time I go to the range. So I'm not changing any aspects about the rifle support or anything also. I also tested out 3 scopes since the off season and have noticed it with each scope. VX-6HD, NF ATACR and NF NX8. So it's either something I'm doing, something my rifle is doing, or normal/common. But 100% not the optics.

Not sure what you mean left/right. is that left to right? or its random and could be left or right. either way I think It's time for a level. Take the possibility of cant out of the equation. I got one of those that is built into the top of the scope ring. its out of the way and easy to pick up with your free eye. Different weather at the range had me wearing different jackets/shirts. ended up affecting how I shouldered the rifle, even from sand bags. The cant became evident when I shot using a lead sled and there was absolutely no left/right poi shift any more. Some caliber/rifle combos will result in spin drift, but that will always be in the same direction. Three questions, what brand scope and how new is the rifle and what caliber/brand. If made by Nosler, I feel that they make a fine rifle. Have you any info/data on the loads you are shooting?

 

[PatriotHenry]

I would almost bet its your setup and hold that is slightly different on the different days. Pay particular attention to trigger follow through.

Besides that culprit you found near the recoil lug. Doom2 took the words out of my mouth. Can you share a picture or explanation of what you are shooting off of? You said it was the same every time. Also are you a right handed or left? this can cause left or right POI if your technique is not perfect. From the one picture, it appears you have a "Fairly" light rifle, if so this will magnify and imperfections in your shooting.

Another note: That caliber is known as a Barrel Burner. So unless you are fine starting over every 800 rounds or so with a new tube, I would quit experimenting if you have enough components for the 1/2 loads(s) you mentioned.

PH

 

[Huntnful]

This is the lane I shoot down. It runs north and south. Sometimes I'd go in am with sun rising on my left and sometimes in the evening with the sun setting on my right. The rifle is 9lbs scoped. I went out early this morning to test out my final load of 180 VLD's at 3200FPS. I intentionally faced west and put the sun at my back this time. I will make sure to repeat this same positioning (sun directly at my back) for the next few sessions and see the results . I know the gun is a barrel burner for sure haha. But developing loads is half the fun. And if it comes at the cost of a $1k barrel swap every couple of years, that'd probably be the cheapest part of the whole sport lol. I have a 300 Norma being built that will be the twin to this gun right now also, then I'll have more stuff to tinker with haha. Thanks for all the info also!! I'm sure I have slight changes in my form also, even though I actively focus on setting up exactly the same. That's why I was a little wary about what else it could have been. Since I've printed many bug hole groups in the middle for multiple months and range trips prior to all my hunts. I think I'm getting down to the bottom of it!

 

[Pro2A]

View attachment 256520
View attachment 256522This is the lane I shoot down. It runs north and south. Sometimes I'd go in am with sun rising on my left and sometimes in the evening with the sun setting on my right. The rifle is 9lbs scoped. I went out early this morning to test out my final load of 180 VLD's at 3200FPS. I intentionally faced west and put the sun at my back this time. I will make sure to repeat this same positioning (sun directly at my back) for the next few sessions and see the results . I know the gun is a barrel burner for sure haha. But developing loads is half the fun. And if it comes at the cost of a $1k barrel swap every couple of years, that'd probably be the cheapest part of the whole sport lol. I have a 300 Norma being built that will be the twin to this gun right now also, then I'll have more stuff to tinker with haha. Thanks for all the info also!! I'm sure I have slight changes in my form also, even though I actively focus on setting up exactly the same. That's why I was a little wary about what else it could have been. Since I've printed many bug hole groups in the middle for multiple months and range trips prior to all my hunts. I think I'm getting down to the bottom of it!

I find shooting from a truck bed causes POI problems. Truck bed is not stable........wind, spotter leaning on truck, dog/wifey in the cab,......

 

[Window]

I have a wby 270 mag that does the same thing. 1988 Mark V laser Mark (1st Weatherby of now many) that's been pillar bedded, action trued with a 28" heavy Krieger barrel. Consistent 1/4" groups but for some reason, every other range trip, group will be 1/4" to 1/2" right and has me scratching my head. I use a lab radar and noticed you had a magneto speed on your barrel. That could be your culprit.

 

[milo-2]

If something is amiss with the rifle, say mating surfaces, any mechanical issue, I would think you would experience some vertical shift as well, not just horizontal.
Have you ever shot a dot drill? 10 dots on a target. One shot each dot, then map your impacts in correlation with the dots. A really good learning tool is do this, build shooting position, fire one shot, get up, pick up the rifle and obliterate your position, pick up rear bag, take a few steps back, then repeat the process till done.
This teaches one to build the same position every time, from rifle manipulation to cheek weld, and repeatability.

 

[Huntnful]

I have a wby 270 mag that does the same thing. 1988 Mark V laser Mark (1st Weatherby of now many) that's been pillar bedded, action trued with a 28" heavy Krieger barrel. Consistent 1/4" groups but for some reason, every other range trip, group will be 1/4" to 1/2" right and has me scratching my head. I use a lab radar and noticed you had a magneto speed on your barrel. That could be your culprit.

Good catch! The magneto throws my groups like 2" high lol. I'm referring to the groups I shoot without that thing. I'm thinking about switching to a lab radar also though.