Can ammo shift left/right POI?

[SlvrDragon50]

I just got some new ammo (factory reloaded) which worked out quite well except for a handful of unfired primers needing a second hit, but pretty much all of my shooting was off. Granted, I haven't shot in about 1.5 months because I was out of ammo and buried with exams, but I have never had so many shots fly wide right before, even when I first started shooting (i.e., never had a problem with thumbing).

In my mind, it doesn't seem possible for ammo to change its POI left and right, only up and down (which I did notice, the bullets shot quite low, but they also shot a whole lot lighter than my Blazer Brass). It's also possible for my sights to have been messed up since I do have fully adjustable rear sights. Then again, I was experimenting with shooting using a slightly different grip keeping my weak hand thumb off the frame of the gun, but I figured that would have caused bullets to hit left, no right (right handed shooter).

Hope that was clear!

[Wobbly]

It may be a flinch from not shooting regularly.

I'm writing you a prescription for weekly shooting outings. Take 2 nurses and call me in the morning.

 

[SoCal]

How big was the right to left spread?  You could try your old grip and check for any signs of key holing.

[IDescribe]

This came up here recently, and there was a group of "Yeah, happens all the time."  And there was a group of "Nope, I've never noticed it, and I'm not sure it's possible."

I'll tell you that the only thing I can think of that would cause a cartridge to change POI in terms of windage is for the bullet to be loaded long enough to be into the lands, and that force causing the the barrel to sit slightly differently in lock up.

[Boris_LA]

While testing different bullets/powders combinations i have noticed the pattern. In 9mm heavier, slower bullets change POI up/left 10-10:30 o' clock. Lighter faster bullets change POI low/right 4-4:30 o'clock. The shift between 115gr at 1150fps and 124gr at 1020fps is about 1-1.25" at 50'.
I now use 124-125gr bullets as standard to avoid POI shift and guns sighted for this combo. while shooting factory 115gr faster ammo to make more brass i expect groups to move to 5 o'clock and don't adjust the sights.
 
For 45ACP the shift is slightly different between 185, 200 and 230gr. Much less horizontal change more like 11 o'clock vs 5 o'clock and mostly vertical shift related to bullet velocity. Matching the velocity with different wight bullets 185 and 200 gr (about 720-750 fps) yields approximately the same POI at 25yrd and about 1" difference at 50 yards. I am lucky that my CZ97B shoots anything from lightest wadcuters to hotter factory ammo with factory springs. My understanding that most 1911s require recoil spring change and tuning for different loads.

[Joe L]

Every time I see a left or right shift it is a change in grip or trigger finger position.  I only see vertical for eyesight or ammo or ammo temperature. 

My suggestion is to not change anything.  Just go out and shoot again this week.  I've learned that it is always me now and something I am doing differently.  Rarely is it the gun or ammo.   

Joe

[Boris_LA]

Joe,
but are you shooting the same AA 115JHP ammo? If this is the same ammo, POI shift left to right is not the ammo related then.

[tdogg]

This for sure happens with rifle loads.  I have some reduced recoil loads for my wife's 7mm08 and they shoot about 2 inches Right at 100 yds.  It always trips me up when out with the wife practicing.

I believe this could also happen in a pistol but I'd bet it's your shift in grip that is the culprit.

Merry Christmas,
Toby

Sent from my XT1254 using Tapatalk

[Boris_LA]

I also agree that for OP without regular practice and established grip  the shift is more shooter related, not the ammo.

[IDescribe]

POI climbs with heavier bullets, not because they are heavier, but because they are slower and leave the barrel later, as the muzzle is just starting to move.  If you're having POI drift left as bullet weight goes up, my suspicion is that your muzzle is drifting left, even if only minutely, as and after the trigger break, and the muzzle is further left when the bullet leaves the barrel the slower the bullet is.  Whether this is the result of the grip not being as neutral as it could be, or the trigger not truly being pulled straight back, or a flinch, or a combo of the three, who knows, but if you're getting a horizontal drift tied directly to bullet weight like that, the pistol is drifting left the moment the trigger breaks. 

This would also explain Stone Hand Joe doesn't see this effect -- because he's the hero of the straight back pull.   I know he does a lot of precision shooting with a lot more bullet weights than just 115gr, so it's not a matter of him not having the opportunity to notice it.

[Joe L]

Joe,
but are you shooting the same AA 115JHP ammo? If this is the same ammo, POI shift left to right is not the ammo related then.

Boris, you are right, if I hold the ammo constant and see a shift right or left it has to be grip related.  But, I have shot some less expensive ammo (not often enough) when training new shooters.  From a rest, two handed grip, I don't see much of a change left or right with various ammo in a pistol.  With a single hand grip, sure the recoil with different weight bullets and with changes in powder or load will move the hits mainly vertical but a little left or right, just predominantly vertical for me.  But I'm thinking the OP's problem is much more dramatic than what we may see with variations in ammo so I am thinking his results are likely not ammo related. 

Rifles are definitely different due to the harmonics changing with load and bullet weight, in my experience.  And don't even ask me about .22's.  They are a challenge unlike any other as far as variations in ammo. 

Joe

[Boris_LA]

I have observed this horizontal shift with different bullet weight/speed change even while shooting rested from the counter, when shooter variable is at minimum influence. Very small shift normally corrected with trigger finger position, but 1-1.25" at 50'? This is done repeatably while ammo testing and i can call there group will land depending on the ammo i shooting for this string. One of the reasons to minimize the ammo selection and standardize on the one load.

In this example correctly sighted for 25m gun shots lower at 50' because of the high mounted red dot with 124rg bullet at 1020-1030fps. If i use factory S&B 115gr with velocity ~1230fps from my gun, group will move 4-5 o'clock to about 5-4 ring.

[Joe L]

Interesting.  I think you have studied this in more detail than I have!  So noted.  I'll pay more attention next time. 

You are right about something else also.  I don't change ammo often and when I do, I'm not paying much attention to small changes in zero.  When NOT changing ammo, its easy to conclude that a change is due to shooter changing something, like grip strength or trigger finger position. 

Thanks for your insight. 

Joe

[SlvrDragon50]

I did try using my old gripping technique, and the only change I really noticed was that my groupings were smaller. Other than that, the average POI was about 2-3" right of POA at 20'. My friend (who is a novice shooter) noticed the same thing.

The thing that made me think it was ammo was because I had two sets of ammo with me. I had 200 rds of factory second remans (the bad ammo in question) and 200 rds of factory reloads, and I was able to shoot much better with the factory reloads. I asked the company what the difference was, and the factory second remans typically just had dings in the casing, and the bullets were fine. I visually inspected a good bunch of them, and I came to the same conclusion, but I know the slightest difference in the bullet shape could cause it to fly weird.

[Wobbly]

I did try using my old gripping technique....

Would that be gangsta style by any chance ?? That would account for the L/R quite handily.