Let's talk about point of impact / zeroing for different shooters

[gtriple]

I've got a stupid accurate Tikka 223 that my wife and I are shooting. For some reason, her groups tend to be slightly lower and to the right of mine. I've read elsewhere on the interwebs that the zero is different for different people. Even some custom gunsmith say that.

But my engineer brain just doesn't see how that's possible. The zero is the point at which the two lines coming directly out of the barrel and scope tube intersect. Therefore there should only be one true zero point.

The only thing I can think of is that one or both of us have an incorrect head position in relation to the scope. Is that the real reason why the zero point is different for two people?

What's the best way to prevent/change this?

 

[SDHNTR]

Head position, shoulder position, trigger pull, recoil response, etc

 

[BBob]

Most everyone holds and controls a rifle, pistol, bow, etc... slightly different through the shot sequence resulting in differing points of impact. It is what is it. What is so hard to understand about that?

 

[199p]

I got a mate and we can stack groups on top of each other

Then my best mate who always want to use mine shoots 2" high 2" right everytime, i put it down to him having a short fat neck

 

[wind gypsy]

Guns are subject to movement from the time the trigger breaks until the bullet leaves the barrel. Shooter can move it in the process of pulling the trigger and following through with that pull and also by imparting different forces and resistance to recoil that occurs before the bullet leaves the barrel. Parallax error can be a thing too.

 

[BigNate]

There's at least two huge differences. Boobs........





and muscle structure. Recoil impulse, head position also have a big impact. That's why being consistent behind the gun is so important. It's hard to shoot someone else's rifle exactly like they do.
If everything is right with the gun and it shoots from a lead sled or similar device, in theory different shooters should be able to make it shoot.
My son recently went to a long range class and shot an unfamiliar rifles at 1k yards and beyond.

 

[Castle Rock]

It is all in the follow through and being neutral behind the gun

 

[5MilesBack]

A few weeks ago I was sighting in a rifle. Got it punching the same hole in the middle of the bullseye at 100 in a lead sled. Then my daughter shot it......5-6" left every time. I'm pretty sure she's pulling with her left hand trying to keep the gun tight and it breaks just a hair left at the shot. There's always a reason.

 

[TxLite]

Is she anticipating the shot? It sounds like maybe she is jerking the trigger or flinching if the shots are low like that

 

[gtriple]

Is she anticipating the shot? It sounds like maybe she is jerking the trigger or flinching if the shots are low like that

I'll try watching her shooting unloaded without her knowing it. Could be a good indicator. I probably also need to do that.

 

[wind gypsy]

A few weeks ago I was sighting in a rifle. Got it punching the same hole in the middle of the bullseye at 100 in a lead sled. Then my daughter shot it......5-6" left every time. I'm pretty sure she's pulling with her left hand trying to keep the gun tight and it breaks just a hair left at the shot. There's always a reason.

Possible. Lead sleds often impact POI because the rifle doesn’t recoil the same or have the same input as when shouldered.

 

[justin davis]

I feel like even for myself my poi changes a touch from prone off a bipod to when I shoot sitting off a tripod. I know it shouldn’t..but it does. Must be me

But with that said makes sense that different people are gonna have different zeros.

 

[MuleyFever]

First time I had my wife shoot my ML we went to the range and she was shooting significantly lower than I did at 100.

This continued with a Howa I bought her. I have a Savage 6CM now that we shoot really close. I put a cheek riser kit on the Savage and wonder if that isn't helping us shoot more similar. Also have a Trijicon on it and wonder if the parallax is better. Women tend to have longer necks so head position will differ from a man in a lot of cases.

 

[Dexter Grayson]

Had a buddy sight in his 11 yo daughters rifle. She proceeded to miss two bucks at 100 yards. Went back to the range and it’s dead on for him, low left 6” for her.

 

[Formidilosus]

I've got a stupid accurate Tikka 223 that my wife and I are shooting. For some reason, her groups tend to be slightly lower and to the right of mine. I've read elsewhere on the interwebs that the zero is different for different people. Even some custom gunsmith say that.

But my engineer brain just doesn't see how that's possible. The zero is the point at which the two lines coming directly out of the barrel and scope tube intersect. Therefore there should only be one true zero point.

The only thing I can think of is that one or both of us have an incorrect head position in relation to the scope. Is that the real reason why the zero point is different for two people?

What's the best way to prevent/change this?

The rifle does not know where it is at in space. A rifle that is fired neutrally with no up/down/left/right torque will recoil the same way, and have the same point of impact regardless of who is shooting it.

However, it takes specific techniques and practice to shoot neutrally, and if one or more likely both aren’t neutral, there will be POI shifts.

 

[TaperPin]

I'll try watching her shooting unloaded without her knowing it. Could be a good indicator. I probably also need to do that.

It’s cool that you can see the slight difference between the two of you - being able to see small things and not have them get lost in the static is one of the big benefits of an accurate rifle.

A lot of good advice above. Odds are pretty good a small flinch, minor body twitch, or other movement is a factor. The rifle moves about the width of a dime or nickel before the bullet leaves the barrel, and the human brain takes 1/4 to 1/3 of second between wanting to squeeze the trigger and actually making the rifle go boom, so there’s time in there for a lot to happen, and it’s a natural human thing to be oblivious to that fraction of a second.

There’s also muscle memory issues for a lot of infrequent or new shooters - until there’s been a lot of trigger time, body movements can sometimes be rather random, like a toddler just learning to walk. If you were to take a new shooter and fire groups from the bench or bipod at the first 10 shots, 100 shots, 500 shots, and 1000 shots, all four groups would be slightly different. Heck, even between 1000 and 2000 there would be a measurable difference. My nephew gets frustrated with the cost of ammo and reloading components and almost stopped shooting regularly - I’ve agreed to subsidize some of his shooting cost if he will dry fire before and after every round down range, and take 5 minutes inbetween each shot. His trigger time is tripled, and the 5 minutes between shots gets him out of position so he’s getting 10x the practice of settling into a shooting position, both muscle memory building activities. My cost is minimal, but years from now he’ll always remember what a difference can be made, shooting less, but in better ways.

 

[Marshfly]

Had a buddy sight in his 11 yo daughters rifle. She proceeded to miss two bucks at 100 yards. Went back to the range and it’s dead on for him, low left 6” for her.

Kids have a ton of trouble putting trigger and hand pressure straight back into the shoulder. Almost all of them. It has to be taught and sometimes they just have to get bigger.

 

[bruceleroy]

The rifle does not know where it is at in space. A rifle that is fired neutrally with no up/down/left/right torque will recoil the same way, and have the same point of impact regardless of who is shooting it.

However, it takes specific techniques and practice to shoot neutrally, and if one or more likely both aren’t neutral, there will be POI shifts.

Came here to say this, but I got beat. Zeroing is a mechanical process of alignment. We screw it up. Stay neutral, stay zeroed, no matter who it is. Like all things, people will mess up everything.

 

[5MilesBack]

Possible. Lead sleds often impact POI because the rifle doesn’t recoil the same or have the same input as when shouldered.

Ya. I shot it prone and on the bench with a bipod and rear bag and impact was the same for me as with the lead sled. She shot prone and was again 5-6" left. She'll figure it out and "get it" after a few more range sessions. I'm also going to have her shoot my bolt 17HMR a bunch as well so she can feel and see what good form will do for her.

 

[mxgsfmdpx]

I'm also going to have her shoot my bolt 17HMR a bunch as well so she can feel and see what good form will do for her.

This is the answer.