Grip pressure and POI Shift

[Clusterfrack]

Can you provide quantifiable data on that?

I’ll try to collect some next time I have a chance. I’d like to verify that too.

[Toonces]

Grip pressure is irrelevant to accuracy to a single round fired.

I wouldn't make an absolute statement to that effect. As soon as the bullet starts moving, the gun starts moving. Differences in grip strength will make differences in the angle of the barrel as the bullet leaves, which will determine where the bullet will impact relative to the sights. The differences are small compared to everything else that determines group placement, I'm not saying inches at 25 yards, but there is some effect. The more accurate the gun and accuracy intensive the task, the more often it will be seen. I've seen it in bullseye pistols and bench rest rifles. It's also why I want people to sight in their own rifles that will be used for big game hunting.

[GJM]

I’ll try to collect some next time I have a chance. I’d like to verify that too.

Some years back, I spent a fair amount of time shooting at 100 yards with a G3 Glock 17. There would consistently be one shot that was different than the rest of the group. Enough so, I experimented with shooting the first shot at a 50 yard steel, and then shot groups at 100. Posted on it, with pictures, here on the forum.

[DAVE_M]

I wouldn't make an absolute statement to that effect. As soon as the bullet starts moving, the gun starts moving. Differences in grip strength will make differences in the angle of the barrel as the bullet leaves, which will determine where the bullet will impact relative to the sights. The differences are small compared to everything else that determines group placement, I'm not saying inches at 25 yards, but there is some effect. The more accurate the gun and accuracy intensive the task, the more often it will be seen. I've seen it in bullseye pistols and bench rest rifles. It's also why I want people to sight in their own rifles that will be used for big game hunting.

So you’re saying you believe the gun can move from the time the primer is struck to the bullet exiting the barrel?

[Toonces]

So you’re saying you believe the gun can move from the time the primer is struck to the bullet exiting the barrel?

Absolutely.

[Clusterfrack]

Absolutely.

See video and links in my post above.

This is a big reason why shooting rifles from a stable prone or bench position is not as easy as just lining up the crosshairs.

[Jesting Devil]

Free recoil affects POI in rifles and pistols, and will typically send the bullet high. In rifles, a heavier gun or a suppressor tends to reduce this. In pistols, a heavier gun reduces this a lot. Typically this is only a couple inches at 25 yds. But some guns seem more prone to stringing as a function of grip and stance. Gen 1 M&Ps are the best example of this. The barrel lockup was apparently not well designed.

I can hit 6” steel at 50 yds with a Shadow 2 gripped loosely. A G34 will send it over the top.

That makes sense, especially as a light, compact .40 (G23) should be even more prone to the effect.

Grip pressure is irrelevant to accuracy to a single round fired.
Grip pressure is relevant to holding the gun still.

Two things matter:
1) The sights are aligned on target.
2) The sights do not move when the trigger is being pressed.

Once the trigger is pressed, you do not physically have enough time to alter the direction of the firearm before the bullet exits the barrel. If your round did not go where it was intended to go, then it was moved prior to the primer being struck.

Grip pressure is entirely relevant to follow up shots.

This is exactly what I thought previously and what I have taught in classes but I am no longer completely sure. I'm not ruling out poor trigger control (width of the group certainly indicates this) but the decided shift straight up when I called the shot fairly close to center was odd.

I'm going to grab some different rental guns to test this when I'm at the range this weekend, from heavy to light and different calibers. The lighter guns with the hottest rounds should show the biggest shift. I'll remember to get photos this time

[DAVE_M]

This is exactly what I thought previously and what I have taught in classes but I am no longer completely sure. I'm not ruling out poor trigger control (width of the group certainly indicates this) but the decided shift straight up when I called the shot fairly close to center was odd.

I'm going to grab some different rental guns to test this when I'm at the range this weekend, from heavy to light and different calibers. The lighter guns with the hottest rounds should show the biggest shift. I'll remember to get photos this time

I would love to see, under high speed video, the gun move AFTER the primer is struck (but before the bullet leaves the barrel). I’d be willing to bet it is so minuscule that the human eye cannot see it in real time, and the shooter moved the gun prior to pressing the trigger completely.

[Toonces]

I would love to see, under high speed video, the gun move AFTER the primer is struck (but before the bullet leaves the barrel). I’d be willing to bet it is so minuscule that the human eye cannot see it in real time, and the shooter moved the gun prior to pressing the trigger completely.

Guns absolutely move before the bullet leaves the barrel. It's Newton's 3rd Law. No one is saying the movement of the gun while the bullet is in the barrel is going to turn an X into a wide right miss or 7 (that's on the shooter). But how much the gun moves under recoil does affect the POI, how much depends on all the rest of the factors.

For example, movement of the gun while the bullet is in the barrel is why revolvers hit high with heavy, slow bullets. The slow bullet is in the barrel longer, allowing the gun more time to elevate in response to the recoil impulse. The increased elevation of the barrel overrides the external ballistics that will have the slower bullet drop more due to a longer flight time.

The most extreme example I've seen was my Ruger No. 1 in 45-70. A very hot load with a 250 grain Barnes X bullet at about 2800 fps hits over two feet low at 100 yards compared to a "normal" 350 grain Lead bullet. It was truly a WFT moment that had me checking my scope ring tightness, scope tracking, and ability to group on target with the normal load before I figured it out.

[DAVE_M]

Guns absolutely move before the bullet leaves the barrel. It's Newton's 3rd Law. No one is saying the movement of the gun while the bullet is in the barrel is going to turn an X into a wide right miss or 7 (that's on the shooter). But how much the gun moves under recoil does affect the POI, how much depends on all the rest of the factors.

For example, movement of the gun while the bullet is in the barrel is why revolvers hit high with heavy, slow bullets. The slow bullet is in the barrel longer, allowing the gun more time to elevate in response to the recoil impulse. The increased elevation of the barrel overrides the external ballistics that will have the slower bullet drop more due to a longer flight time.

The most extreme example I've seen was my Ruger No. 1 in 45-70. A very hot load with a 250 grain Barnes X bullet at about 2800 fps hits over two feet low at 100 yards compared to a "normal" 350 grain Lead bullet. It was truly a WFT moment that had me checking my scope ring tightness, scope tracking, and ability to group on target with the normal load before I figured it out.

I’m aware it moves. It’s negligible.

However, the original post I quoted said that lightweight guns cause the POI to be “several inches high.”