Grip pressure and POI Shift

[Robinson]

That's messed up man.

I know. I'm pretty sure it's just me. You'd think the difference in recoil would make the 9mm 1911s much easier to shoot well. Hence folks referring to it as "cheat mode" right? Went to the range again today though, and my targets told the above tale.

What I should probably take away from this is that I need more practice with the 9mm 1911s. I have sort of been neglecting them for the G34s the last few months. The .45 thing might just be familiarity with its shooting characteristics from all the years I spent shooting and carrying them. I dunno.

[1slow]

Agree.

Also, POI from a rest will often not be the POI offhand. Whether an inch or two at 25 is a big deal or not depends on what you need to shoot.

While we are on this topic, how you chamber the round can affect your POI too. (Press checkers take note).

FAL rifle (tilting bolt ) shooters have sometimes noticed vertical changes in POI depending on how many rounds are in the magazine and how this affects spring tension pushing up on the bolt and thus affects bolt lockup.

In a Browning tilting barrel lock up, I would think how hard the slide closes could possibly affect barrel vs slide alignment and thus whether the bore aligned consistently with the sights.

[1slow]

IMHO guns , both pistol and rifle, that are light for their caliber, change POI more with variations in hold.

[Jesting Devil]

So I'm not sure this proves anything conclusively. Tested 3 guns and was planning to test 2 more but the lane I was using on my lunch break broke (yay indoor range). All guns are rentals, stock with stock sights and well worn by daily use. I shot 1/2 magazine through each with a loose grip followed by a solid, tight grip.

Guns tested: Sig P226 - 9mm, Glock 43 - 9mm, Sig 1911 - .45
Ammo: 9mm Blazer aluminum 115gr. FMJ .45 Winchester 230gr. FMJ
Target Photos: 1st - Loose grip 2nd - Firm grip

Results: I'm suspecting that my initial group shift was more a fluke of trigger control than one of recoil physics. I saw no evidence of a loose grip causing a shift in a particular direction although groupings were decidedly better when gripped firmly. I will test the original gun (Glock 23, NY trigger) again along with my tuned CZ SP01 later on for some final data points.

Added Notes: The 1911 had the best sights and trigger in my opinion and was the most confidence inspiring. The 226 choked hard every shot on the Blazer aluminum ammo when gripping loosely and 2 more when gripping harder. The G43 had no problem with it.

[Clusterfrack]

Ok, I'm back from the range with a big mouth full of crow feathers. @DAVE_M is correct. In a Gen 4 G34 with a KKM barrel, stabilized on a table, I cannot measure a POI shift between the following:
-Gripped tightly
-Gripped loosely
-Held just by the bottom of the grip so the gun flips a lot (this caused stovepipes and FTFs)

A tighter grip did cause the group to be tighter.

I also confirmed the same thing using a Shadow2.

I'm really glad to have cleared this up so I can stop passing on incorrect information.

Here is a 10 shot target from the G34 at 20 yds. 5 shots centered in the paster are gripped tightly. The more widely scattered hits are loosely gripped. Note that there are some doubles (2 shots one hole) on this target. The low one was a bad trigger press.

I’ll post some pistol data within a week. I’m glad to have a reason to quantify this.

Regarding rifles, it’s really not debatable that recoil control affects POI.

[Toonces]

Ok, I'm back from the range with a big mouth full of crow feathers. @DAVE_M is correct. In a Gen 4 G34 with a KKM barrel, stabilized on a table, I cannot measure a POI shift between the following:
-Gripped tightly
-Gripped loosely
-Held just by the bottom of the grip so the gun flips a lot (this caused stovepipes and FTFs)

A tighter grip did cause the group to be tighter.

I also confirmed the same thing using a Shadow2.

I'm really glad to have cleared this up so I can stop passing on incorrect information.

Here is a 10 shot target from the G34 at 20 yds. 5 shots centered in the paster are gripped tightly. The more widely scattered hits are loosely gripped. Note that there are some doubles (2 shots one hole) on this target. The low one was a bad trigger press.

Interesting...did you do any testing at ranges longer than 20 yards? I’ll take some pistols and way more accurate than I am and test at 50 yards, Soon(tm). I’ll document with pics and report back. It it turns into a victory lap for @DAVE_M I’ve got a minivan that seats eight and I’ll buy the first round.

(This post is the third attempt. I tried twice from my PC and was rejected by my antivirus. )

[Clusterfrack]

Interesting...did you do any testing at ranges longer than 20 yards? I’ll take some pistols and way more accurate than I am and test at 50 yards, Soon(tm). I’ll document with pics and report back. It it turns into a victory lap for @DAVE_M I’ve got a minivan that seats eight and I’ll buy the first round.

(This post is the third attempt. I tried twice from my PC and was rejected by my antivirus. )

I thought carefully about what distance to use. I wanted a precise aiming point that couldn't be affected by lighting. These results are hard to reconcile with my past experience, but as they say the bullet doesn't lie. I still expect some guns will show a POI shift as a function of grip, but unless we have hard data...

[UNM1136]

I kinda stayed out of this, reading but not posting. It seems to me that a relaxed grip changes the basic trigger finger movent and the support for the platform as the trigger finger moves through the trigger press. I am not certain that a shooter setting up a high speed camera would necessarily be best positioned to capture those minute motions, particularly during the normal wobble during off hand shooting.

In Santa Fe, the DPS Academy has a magical camera system that attaches to the pistol and the head of the shooter, similar to what the demo guy with the AMU uses in his shot calling video elsewhere on the site. It shoots 60 frames per second, and records multiple points of view for diagnosing shooter errors. It seems to me that this would be ideal for this situation. But, 10 years ago it was a $120,000 gadget that apparently was on safari to photograph unicorns. I have heard its virtues, but never been allowed to see it in use.

Those skilled enough to call their shots at a high level and high volume would likely know when their shots were that far off, while those less skilled might not be fully aware of several inches at 50 yards.

I don't think I have an aswer, just a theory I will likely never be able to test.

pat

[Clusterfrack]

Here’s a link from a recent discussion on Enos Forum that confirms my understanding that recoil affects POI. It’s not a large effect, but measurable at distance. FYI Guy Neill is a USPSA shooter and had a career in ammunition manufacturing and testing.

https://forums.brianenos.com/topic/2...major-results/
Guy Neill:

“Slower bullets will be in the bore longer, allowing the muzzle to rise more before the bullet exits, resulting in higher impact point compared to the faster load. Not knowing the range, it's hard to say if the 1" difference is reasonable. For a 45 fps difference, it seems more than expected at handgun ranges.”

[LSP552]

Here’s a link from a recent discussion on Enos Forum that confirms my understanding that recoil affects POI. It’s not a large effect, but measurable at distance. FYI Guy Neill is a USPSA shooter and had a career in ammunition manufacturing and testing.

https://forums.brianenos.com/topic/2...major-results/
Guy Neill:

“Slower bullets will be in the bore longer, allowing the muzzle to rise more before the bullet exits, resulting in higher impact point compared to the faster load. Not knowing the range, it's hard to say if the 1" difference is reasonable. For a 45 fps difference, it seems more than expected at handgun ranges.”

My primary carry P226 has a 2” height difference between 124+P and 147 Gold Dots at 25 yards. The 124s are lower and the 147 zero perfectly. Gun has Trij HDs. My 239, zeros with the 124+Ps and shoot the 147s higher than I like. My 228 zeros with 147 and low with the 124+Ps (Sig X-Ray 8/8).

My Glocks shoot higher with 147 than 124 +P also. I’ve decided that keeping some different ammo is better than chasing sights across a bunch of different guns