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Old September 21, 2012, 12:02 PM   #1
geetarman
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Join Date: November 18, 2009
Location: Arizona
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Major change in CZ452 POI

The rifle is a CZ 452 Trainer
The scope is a Nikon Monarch 4-16X50 on a picatinny rail.
Ammo is CCI Mini Mags.


I shot nice 10 shot groups last week with this rifle at 100 yards. Groups were a little larger than a quarter.

Brought the rifle home and set it on the mat in my garage and bore snaked the bore.

This morning, I took the NRA standard 100 yard target and posted it at 100 yards.

Imagine my surprise when sighting the top left target, I actually hit the middle target.

That is a 4 inch shift in POI at 100 yards.

I dialed in 16 clicks left adjustment and the hits moved just where they were supposed to.

I checked the scope ring screws, the base screws and the mounting screws in the bottom of the stock.

I did find two screws on the scope rings that were not loose but they were also not as tight as I normally tighten them. I also locktite them.

The rings are Warne and this is the same scope I have been shooting on an M1A with no issues at all.

Do you guys think this is just a fluke? I cannot imagine a bore snake affecting windage. Elevation yes. I have not changed ammo. As a matter of fact, I was using the same lot of ammo I used last week in the magazines I loaded last week.

Because I did retighten those two screws, I brought the target back to 50 yards and had to take a lot of elevation out.

Once I got it on the ShootNC again, I shot 5 more 10 shot groups that are a little smaller than a quarter.

I am happy with the rifle and went down to the gunsmith on the range and showed him what I have.

His advice is to take it back out to 100 yards next week and see if it happens again. He suspects the scope adjustment may be hosed up although this scope has no history of problems on a .308.

The rifle, to my knowledge, has not been bumped and was untouched over the week.

Where would you guys look?

Maybe mount another scope and rebore sight and take it to 50 for a tune in and then back out to 100?

I can't wrap my arms around a 4 inch shift in POI at 100 yards unless something majorly slipped.

What do you think?
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Old September 23, 2012, 12:28 PM   #2
DnPRK
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Did you take the barreled action out of the stock to clean it?
Was there a difference in the temperature when you shot?
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Old September 23, 2012, 12:56 PM   #3
geetarman
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No. The only thing that has happened this past week is the air drying out. The monsoon season is going away.

I will be going back to the range Friday to see if there is another shift.

I did not shoot the rifle very fast and heat should not be a major issue.

I do wonder if the windage adjustment might have hung up. The scope has really been trouble free and has seen service on my M1A.

The thing is, the elevation was still spot on. Only the windage had changed.

Had it only been a small amount, it would not be an issue, but 4 inches is a LOT.

Even different lots of ammo would most likely have changed elevation. . .not windage.

There was no wind to speak of either day.

If there is another shift, I will readjust scope and tap the turret to reduce backlash and reconfirm zero.

I do not know how tight the bedding screws should be but they were not loose and moderate pressure did not move them.

One thing I can do, now that I think of it, is to put the laser bore sighter in the gun and deliberately turn in a bunch of windage and then take it back to zero without going past zero. Then tap the turret and see if there is a change.

It may be the adjustment needs to be made in one direction only.

I know from past experience with musical instruments, you never adjust a string down to pitch and leave it. You ALWAYS tune below and bring the string up to pitch and tension the adjustments with the load in the same direction.

I will see what happens come Friday.
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Old October 5, 2012, 05:33 PM   #4
geetarman
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Here is the latest on my problem with the CZ452.

Had it out to the range last Friday. Still shooting CCI MiniMags and got the rifle zeroed at 50 yards and was stable.

Moved out to 100 yards and only had to dial in the elevation. Got rifle zeroed at 100 yards.

Checked the rail mounting screws, checked the ring screws and tapped the adjustment just in case something was hanging up.

Rifle shot fine.

Went to the range this morning and put my target up at 100 yards and rifle was just about perfect. Probably shot 30 or 40 shots.

A friend of mine showed up and wanted to look at the rifle. I was reloading some magazines.

I asked him if he wanted to try it out. He did and on my target board I had two little 3 inch or so Shootncs and he said he would try for the upper right one. First two shots. . .not even close.

He shifted to the 7 inch target and was shooting almost two inches to the left.

He did not change anything on the scope. I figured he was just seeing the target differently than me.

So I took a turn at the little three inch target and I did not hit it either.

I went back to the seven inch target and aimed at the right edge with elevation on the little red dot on the target and . . .hit the center!!!

I tapped the scope and went to a clean 7 inch target and was hitting all the way over at the left edge. I was aiming at the center this time.

Still shooting the same lot of CCI ammo and rechecked the mounting screws and nothing seems adrift.

The barrel hardly seems warm and is by no stretch hot.

The wind was not much different than last week and certainly not drastically changed from the time I started shooting at 7am and finished at 8:15.

With this updated info, any of you have an idea where to look?

I am baffled.
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Old October 5, 2012, 06:17 PM   #5
603Country
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I had a similar problem with a Nikon 4x16-40mm. In my case it was the scope, which was replaced with a Leupold vx2 6x18. I burned a ton of ammo until I figured that it had to be a scope problem. it was.
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Old October 5, 2012, 07:08 PM   #6
geetarman
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I think I am going to have to change the scope out and see if the problem goes away. Pretty disappointing if that is the case. The scope had been on my M1A and had no problems.

I have a couple of different scopes already in Warne rings set up for a picatinny rail. I will swap one out and see what happens.

Thanks for the reply.
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