POI Shift Between Ammo Types?

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coleman1495 said:
That’s exactly what I’m used to seeing.
Only good thing is that if you want to prank your buddy, just switch ammo on him. He’ll be wondering why his shots are way out.
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Nothing like going in a turkey shoot and the guy hands you 5 rounds and some of which are a different brand. Not sure if they have turkey shoots in your area, but they used to be popular in Manitoba. Best group wins a turkey.
 
B said:
You can think whatever you like, it doesn't change the fact 3" is not incredible. If your other guns usually only shift 1-1.5" then that's great, your CZ still isn't broken.
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Okay but 3” is unacceptable to me, my original question was whether I should be looking at barrel or stock.
 
^^^ Or your barrel cleaning (or lack of it). Or your barrel conditioning with fouling shots (or lack of it). Or your expectations. Or the ammo that you are using. All can explain what you are experiencing? Or go ahead and have a new barrel or new stock installed and tell us if that made a difference.

For perspective - is a bench rest shooter guy that I correspond with from Winnipeg - when evaluating different ammo lots - he said he has at least 5 or 6 times 10 shot groups - plus initial fouling shots - and then thoroughly scrubs and cleans the bore before trying the next batch - clean the bore, foul it with new stuff, then 5 x 10 shot groups - to form an opinion. Up to that point, he does not feel he has enough valid information to make a choice. He has won (and not won) several competitions, to arrive at that process. Is way, way past anything that I have tried to do, but perhaps gives you a perspective on what some people do to arrive at the conclusions that you have arrived at.
 
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coleman1495 said:
Unless by the ammo you mean to shoot the same type so I don’t have a POI shift.
Not sure whats confusing folks here. I’m getting abnormally large POI shifts between ammo types.
No its not between drastically different types either.
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Not all ammos will have the same point of impact from the same barrel, even ammos that are "rated" from the factory as having identical or nearly identical muzzle velocities. There are other factors that influence POI other than MV.

A few questions in an attempt to bring some clarity.

First, do all different ammos have a 3" POI shift? If not, what ammo showed a 3" POI shift from what other ammo?

Second, how many times was the 3" POI shift experienced when changing to the ammo(s) that had the large shift? In other words, did you shoot one or two groups that seemed to strike out of place? Or does this 3" shift happen with across many groups shot with the guilty ammos?

If it happened once or only one test was made, then it's a non-issue.
 
grauhanen said:
Not all ammos will have the same point of impact from the same barrel, even ammos that are "rated" from the factory as having identical or nearly identical muzzle velocities. There are other factors that influence POI other than MV.

A few questions in an attempt to bring some clarity.

First, do all different ammos have a 3" POI shift? If not, what ammo showed a 3" POI shift from what other ammo?

Second, how many times was the 3" POI shift experienced when changing to the ammo(s) that had the large shift? In other words, did you shoot one or two groups that seemed to strike out of place? Or does this 3" shift happen with across many groups shot with the guilty ammos?

If it happened once or only one test was made, then it's a non-issue.
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Yes for the tenth time I realize different ammo will have a different POI. Again, the issue is that the shift is huge.

Off the top of my head, the Aquila “Spec Ops” from CanAm and mini mags had a huge difference in POI. I experienced a large shift across a bunch of different types. This shift will happen every time you switch ammo.

For the last time, the POI shift Im seeing is much more than expected

Question is why?
 
coleman1495 said:
. I experienced a large shift across a bunch of different types. This shift will happen every time you switch ammo.

For the last time, the POI shift Im seeing is much more than expected

Question is why?
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How about it's not the ammo and your barrel is screwed, perhaps literally. Without going through the minutiae of this thread, it's important to check the barrel retention grub screws to ensure that they are both equally torqued to a proper level -- about 30 inch pounds (not foot pounds).
 
Data would help to explain what you mean, because no one here thinks anything is abnormal.

This link provides a free downloadable and printable PDF quadrant target. A quadrant target is designed to measure group POI from the central point of aim.

https://accurateshooter.net/targets/boxesloaddev.pdf

If this target won't work for your demonstration of what you are talking about, its easy to make your own target design.

I suggest you shoot 10-shot groups for all your ammo brands. Unless you are lucky to have an indoor shooting range, technically you need to do this on the same day in the same environmental conditions, documenting if the wind speed and direction changes. Don't even try on a very windy day. Chose a low wind day. Even in low winds, a sideways gust of wind on a 50m range can easily move a round 1 to 2 inches from point of aim. You need at least 10 shots per group to show any sort of consistent group location, and to identify crazy fliers that a wind gust may cause, or that is inherent in bad rounds in most boxes of ammo.

You may want to do replicates of these 10-shot groups, because believe it or not, 10-shot groups with the same ammo can move for unknown reasons.

Its a given of course that you use bench rest technique to eliminate as many variables as possible. A steady bench (preferably concrete on a concrete floor), heavy, rock solid front rest (NOT a tactical bipod), or use an F-class style wide stance bipod on skis that can free recoil smoothly (like an MPOD), and rear rabbit ear bag, and that you use consistent shooting technique (I recommend free recoil method).

And you need to shoot several fouling shots of each new ammo brand in a sighter target to re-condition and re-warm the barrel to the new lube and powder combination before shooting the 10 shots for record.

Looking forward to seeing your results.
 
coleman1495 said:
Yes for the tenth time I realize different ammo will have a different POI. Again, the issue is that the shift is huge.

Off the top of my head, the Aquila “Spec Ops” from CanAm and mini mags had a huge difference in POI. I experienced a large shift across a bunch of different types. This shift will happen every time you switch ammo.

For the last time, the POI shift Im seeing is much more than expected

Question is why?
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Like said call CZ. They might have your answers.

But don't get pissy for people trying to help, when you are giving vague answers. Remember we are not there, we dont see the groups, we are not seeing measurements, or ammo used.
 
Bulk .22 LR is hardly being made to any tolerances anymore. I would discount any POI problems with those, except to avoid them when accuracy was vital. If however match quality rounds are showing huge differences I would blame the rifle but fill up a notebook with data about which ammo shoots were.
 
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