Same handgun, different POI for two shooters?

[Randy Harris]

Voodoo mentions ammo....and bullet weight makes a difference.

In my own situation a glock 34 zeroed with standard 115 gr ball (CCI Blazer Brass) will throw a 124 grain bullet a little bit high and to the left (I'm right handed) of my POA. A 147 in the same gun goes even higher and even more to the left. BUT...a 124+p (faster bullet) goes a tiny bit to the RIGHT. If aiming at a Shoot n See paster (like 1" diameter) I am right on the paster with 115, about a half inch high and left (11o'clock) with 124 and about an inch to 1.5" high and left (11 o'clock) with the 147 at 7 yards. But as distance increases they will get farther to the left and higher.

Now, would most people even notice? No. If your group on a B8 at 7 yards looks like a shotgun pattern then you are probably never going to even notice this. But if you are used to putting them all through one hole and then suddenly that hole has migrated high and left (in my case) then it may well be the difference in bullet weight. I asked Tom Givens about this. I told him I'm pretty sure I know why it is high because the gun is starting to recoil before the bullet is out of the barrel with the slower moving bullets so that makes sense. But I wasn't sure about them going left. His opinion was that most people push the gun one way or another (whether they realize it or not) and the slower bullet was just getting "pushed more" because it was slower getting out of the barrel.

Moral of this story....zero carry guns with carry ammo ONLY and zero match guns with match ammo ONLY and don't switch bullet weights if you expect to still be able to drive nails or hit flies.

[rdtompki]

Same height? No
Use the sights same way? yes
Same eye side dominant?yes
Squeeze trigger correctly?yes
Grip similar?Yes, but wife has some prior damage to support hand which I would expect to cause a slight issue at speed. We observed the slightly left of center hits with a Kimber HD Pro Carry in 9mm which is a pretty steady gun with factory ammo
Same ammo?yes

We'll play around with this some more. The trigger is a bit heavier than her competition gun at 4lb/6oz versus the 3lb full-size 1911.

[voodoo_man]

Get someone who you know for a fact is a good shot and have them shoot the gun.

Btw you guys should be testing this at 25y and not much closer as at that distance you will see any real difference in accuracy standards. If you are shooting at 7y and one of you is drastically off then that's the person not the gun, most likely.

[voodoo_man]

Voodoo mentions ammo....and bullet weight makes a difference.

In my own situation a glock 34 zeroed with standard 115 gr ball (CCI Blazer Brass) will throw a 124 grain bullet a little bit high and to the left (I'm right handed) of my POA. A 147 in the same gun goes even higher and even more to the left. BUT...a 124+p (faster bullet) goes a tiny bit to the RIGHT. If aiming at a Shoot n See paster (like 1" diameter) I am right on the paster with 115, about a half inch high and left (11o'clock) with 124 and about an inch to 1.5" high and left (11 o'clock) with the 147 at 7 yards. But as distance increases they will get farther to the left and higher.

Now, would most people even notice? No. If your group on a B8 at 7 yards looks like a shotgun pattern then you are probably never going to even notice this. But if you are used to putting them all through one hole and then suddenly that hole has migrated high and left (in my case) then it may well be the difference in bullet weight. I asked Tom Givens about this. I told him I'm pretty sure I know why it is high because the gun is starting to recoil before the bullet is out of the barrel with the slower moving bullets so that makes sense. But I wasn't sure about them going left. His opinion was that most people push the gun one way or another (whether they realize it or not) and the slower bullet was just getting "pushed more" because it was slower getting out of the barrel.

Moral of this story....zero carry guns with carry ammo ONLY and zero match guns with match ammo ONLY and don't switch bullet weights if you expect to still be able to drive nails or hit flies.

If you are talking about pinpoint duty accuracy then yes I completely agree. Hostage taker face shot level type of accuracy, totally.

Minute of pie plate, is probably good to go for the average shooter.

If we are talking about accuracy under high stress then I think people put a little too much into bullet weights and all that. I'd love to see someone do a study on group sizes vs gun vs ammo under stress. Though I believe the answer will be "a lot" and "everywhere."

[jetfire]

I've noticed that people tend to read sights differently, and where I have my sights zeroed on pistols may not work for someone else. You'd think it would all be the same, but in my experience it's not. That's why a gun set up for me may not hit the same spot for you.

[SLG]

As mentioned before, same gun same ammo, equally skilled shooters, hits to different points, not because of sight issues (usually), but because of how the shooter interfaces with the gun. Same with precision rifles and top of the line scopes. A zero'd gun is a zero'd gun, but due to mass and technique, it will recoil differently for each shooter and put the bullet somewhere else. Same thing happens with pistols, though usually on a smaller level. I find I can basically hit poa/point with anyone's gun, as long as it it actually zero'd. Many are not.

[nwhpfan]

I've noticed that people tend to read sights differently

Amen.

Before Dr. Gabe comes along and talks about convergence et, al - the fact is what one person thinks is dead center in the rear sight notch is not to the next person because their eyes just don't always see it the same.

[GRV]

As mentioned before, same gun same ammo, equally skilled shooters, hits to different points, not because of sight issues (usually), but because of how the shooter interfaces with the gun. Same with precision rifles and top of the line scopes. A zero'd gun is a zero'd gun, but due to mass and technique, it will recoil differently for each shooter and put the bullet somewhere else. Same thing happens with pistols, though usually on a smaller level. I find I can basically hit poa/point with anyone's gun, as long as it it actually zero'd. Many are not.

From a training perspective, how useful is the concept of a pure, human-free, mechanical zero?

I get what you're saying here. It's also true though that someone can be bad, but consistently bad, like a consistent flinch or grip issue. I've shot tight groups before that were off mark. How does one know if your "zeroing" is really just masking some problem (trigger pushing or something) vs actually correcting for mechanical relationships? Moreover, for real-world use, does the difference even matter?

From a training perspective though, in order to make sure the gun is really telling me what I'm doing and not entrenching bad habits, I've often felt that I couldn't trust myself to zero my own pistol, and I've tried to find ways to remove myself from the equation. See for example, the iconic Glock shooter whose pistol is "zeroed" with the rear sight pushed all the way to the right...

[SLG]

From a training perspective, how useful is the concept of a pure, human-free, mechanical zero?

I get what you're saying here. It's also true though that someone can be bad, but consistently bad, like a consistent flinch or grip issue. I've shot tight groups before that were off mark. How does one know if your "zeroing" is really just masking some problem (trigger pushing or something) vs actually correcting for mechanical relationships? Moreover, for real-world use, does the difference even matter?

From a training perspective though, in order to make sure the gun is really telling me what I'm doing and not entrenching bad habits, I've often felt that I couldn't trust myself to zero my own pistol, and I've tried to find ways to remove myself from the equation. See for example, the iconic Glock shooter whose pistol is "zeroed" with the rear sight pushed all the way to the right...

Matter? Got me. All I know is that I have fired literally a thousand other people's guns over the last 20 years, most of them at work. With very few exceptions, they all shot on for me, as long as they did for them. Those guns were mostly "zero'd" from the armorer or factory. That means relatively little, especially with all the issues some sight manufacturers have foisted on us. Nonetheless, to my mind, zero'd is zero'd. The inconsistency is usually the loose nut behind the gun.

Usually.

[GRV]

Matter? Got me. All I know is that I have fired literally a thousand other people's guns over the last 20 years, most of them at work. With very few exceptions, they all shot on for me, as long as they did for them. Those guns were mostly "zero'd" from the armorer or factory. That means relatively little, especially with all the issues some sight manufacturers have foisted on us. Nonetheless, to my mind, zero'd is zero'd. The inconsistency is usually the loose nut behind the gun.

Usually.

Does that include precision rifles?