Wandering Zero?

[AzNooB]

It seems like the last 3 times that I've verified zero on my CZ Shadow equipped with an adjustable rear sight, the zero has changed significantly each time. I always zero my gun using the same ammo (Federal 147gr FMJ) at 25 yards and generally print 3-4 inch groups. 

 

• The first time was at an indoor range where it was dark and I zeroed it on the head box (Aiming at the "0") of an IDPA target.
• The second time I shot on an overcast day on a B8 target. I had to adjust around 3-4 inches lower than the previous zero.
• The third time was on a sunny day and I used the head box (aiming at the "A") of an IPSC metric target. This time, I had to adjust 3-4 inches to the left from the previous zero.

 

After zeroing, my shots will be dead on for the entire day and my rounds will go exactly where I aim.

 

The obvious variables here are the targets and the lighting conditions. Do these really have that much of an affect on a pistol's zero? This would mean that I should ideally zero my pistol before each match in the same lighting conditions as the match. I really don't like treating my pistol like a precision rifle and I'm wondering if there's something else I'm missing here. 3-4 inches off at 25 yards makes a big difference, especially when it's windage.

[Hi-Power Jack]

Either the sunlight (lighting conditions hitting your front sight),

 

Or

 

Your sight is loose (I had that problem with my Gold Cup 10 years ago)     

[g mac]

maybe, Tighten the "nut" behind the gun?LOL..just kidding.....  Could be eyesight due to lighting conditions?  zeroing sitting down vs standing?  I noticed a shift on point of impact when I zero sitting down, then standing up.  Other variables, grip, trigger control, handgun technique inconsistency, fatigue, etc

[IHAVEGAS]

On 3/5/2018 at 2:02 PM, AzNooB said:

 

The obvious variables here are the targets and the lighting conditions. Do these really have that much of an affect on a pistol's zero?

 

Not unless you are doing something different with sight alignment &/or trigger control &/or anticipation.

At 25 yards it is easy to be doing things just different enough to move poa a bit, usually trigger control.