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Old October 14, 2012, 09:15 PM   #1
chris in va
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Groups left.

My gun was grouping left, verified off a bench. The rear sight was lightly staked from the factory with the assumption it shot POI at that position. It was off about 3" at 30'.

I shoved it over to the right about 1.5mm and now get dead-on shots. Unfortunately being the Virgo I am, this bothers me with the rear sight being offset enough to be quite noticeable.

What causes this to happen? I'm using my LRN reloads.
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Old October 14, 2012, 09:18 PM   #2
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Some details like what manufacturer, model, and caliber might help...
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Old October 14, 2012, 11:56 PM   #3
chris in va
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I doubt it would make any difference, but...

CZ P01.
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Old October 15, 2012, 12:03 AM   #4
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I've got a few like that. You just have to decide which bothers you more--off-center groups or off-center sights.

It could be a number of things--even from a rest, trigger technique can push/pull groups one direction or another. Or it could just be that your gun shoots a little left.

CZ used to include a test target, or a test target representation with each gun they shipped. Might be interesting to see what it looks like.
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Old October 15, 2012, 02:17 AM   #5
chris in va
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I checked the test target. Two shots were completely off the rectangle to the left, the other three inside but above-right. I don't think they were using a machine rest.

Dispersion area was 80mm at 25m.

Last edited by chris in va; October 15, 2012 at 02:24 AM.
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Old October 15, 2012, 06:40 AM   #6
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What you describe can be an issue with any gun.

I bought a brand new Dan Wesson Valor that shot 2 inches to the left for me at 15 yards.

I had that verified by two other shooters.

I went to the CZ custom shop and asked them to push the rear sight over
.020 inch.

I went back to the range and it is dead nuts now.

Sometimes it is the shooter and sometimes it IS the gun.
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Old October 15, 2012, 07:27 AM   #7
g.willikers
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My money's on shooter error.
Re positioning the sights will only obscure the problem.
When multiple people shoot it the same off center way, it might be an overly large grip that needs to be changed.
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Old October 15, 2012, 08:00 AM   #8
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Quote:
I doubt it would make any difference, but...

CZ P01.
I asked because some manufacturers, such as CZ, include test targets. Also some manufacturers are better at warranty work, more willing to take a gun back in, than others so I am more apt to recommend returning to the manufacturer in different cases.

I'd say one quick test would be to have a fellow shooter that you know is somewhat experienced fire the weapon as well. If he can replicate the error than the chances that it is user error get that much smaller. From what I hear CZ has excellent customer service should you need to send it in. If you do, make sure to send your own test target as well.
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Old October 15, 2012, 08:04 AM   #9
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Yes, when i shoot a handgun, particularly a new one, I shoot it every different way I can think of. Isosceles stance, weaver, one handed (if reasonable), weak handed, I also switch between eyes.

I can shoot most handguns with either hand, and use either eye, doing this has often told me that the reason I was not hitting where I wanted was because of me, not the firearm. Then I could troubleshoot from there
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Old October 15, 2012, 11:47 AM   #10
chris in va
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Going to the range again today...I'll try out some FMJ along with the usual LRN and shoot off a rest like last time.

I guess I'm just wondering if the barrel/slide relationship can be skewed that much from the factory.
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Old October 15, 2012, 11:56 AM   #11
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Quote:
Going to the range again today...I'll try out some FMJ along with the usual LRN and shoot off a rest like last time.
There's no one you can bring with you, maybe even ask the range officer if there is one? Best way to solve a problem is to isolate the variables one at a time. It very likely isn't you, but having someone else shoot it and replicate the problem sure backs up that idea.
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Old October 15, 2012, 10:02 PM   #12
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80mm is about 3.1" which isn't awesome accuracy for 25m (27.3yds) but it's definitely not bad either.

Is the overall test target group centered, or is it off in terms of windage? If it's off, by how much?
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Old October 15, 2012, 10:28 PM   #13
chris in va
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I spent some time getting it zero'ed today. Looks like I tapped the sight too far right the first time, so it only needed about a milimeter off it's factory setting. I managed to get a nice 2" cluster at 25 yards, not bad considering I have astigmatism and see a ghost image.

Whew.
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Old October 16, 2012, 12:34 AM   #14
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Beating the test target isn't easy in my experience--sounds like a good day's work.

Assuming the sight radius is pretty close to the same as the CZ75B (6"), a 1mm windage adjustment to the sights should result in a point of impact difference of 5.9" on a 25 yard target.

At 10 yards, a 1mm windage adjustment would move the point of impact about 2.35".

Going back to the test target, if the sights were off by 1mm, the group on the test target shot at 27.3yards should have been off-center by about 6.5".
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