The Original CZ Forum
CZ LONG ARMS => CZF RIMFIRES => Topic started by: Oldevo on January 17, 2016, 08:37:41 AM
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New CZ shooter here. I recently bought a 452 Ultra Lux and found that I could not zero at 50 yards. Even with the rear sight all the way down and the front post all the way up at the top of the ramp it shoots 4- 5 inches high. Ammo is CCI Mini Mag.
The front sight post is a #1. I ordered #2 and #3 posts from the CZ store but it seems that order has gone astray.
Anyone know which is the correct sight for this gun? I could just get the tallest post they make and file as necessary.
The test target had the group within an inch of the POA. Maybe the test firing is done in a jig that does not require actual sighting of the gun.
Or maybe I don't have a clue.
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There is a formula to determine the height of a front sight based on the sight radius and the amount you want to move the point of impact. Brownell's has an easy to use calculator... http://www.brownells.com/GunTech/Sight_Correction_Calculator/detail.htm?lid=13093 I'd move the front sight to the middle of the adjustment range before determining the sight radius.
Also, the test target was fired using standard velocity ammo, I believe. If you are using HV ammo your point of impact would be higher, but you'd think there would be enough adjustment in the system to regulate for that.
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Thanks, that will help. I think I will also measure the vertical range of the front sight ramp. I will be using either SV or HV ammo (no subs) and try to split the difference.
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I think using the sight radius in the middle of the adjustment range accomplishes the same thing.
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You're right, it will. Knowing the actual vertical adjustment range just makes future changes a little easier. Or so my OCD self tells me.
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Knowing the difference in height between reference marks on the ramp would tell you more...or so my OCD self tells me. ;)
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Good idea!
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Well, no scale on mine. I must have seen a picture of one with a scale and remembered it as mine. Anyway I get 2.3 mm vertical range. The Brownell calculator shows 1.37mm (converted from inches) of correction needed. Since I will raise the rear tangent sight to the 50 yard position that adds .41mm. So call it 1.8mm additional on the front sight. Looks like a #3 sight post set down the ramp a little may be close for the HV ammo. Maybe the remaining downward adjustment on the front sight ramp will cover SV ammo.
#1 .278" 7.06mm
#2 .316" 8.03mm
#3 .366" 9.30mm
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I think it will be too tall, but that's easier to fix than not tall enough. ;)
Good luck.
edited to add...
My 452 Lux has graduations on the left hand side of the ramp and an index on the center of the blade base. I guess that those were done away with over time.
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This is a cut and paste from rimfire central
CZ Tangent sight info
There is no "set position" ... the front sight is adjustable for a specific reason. Namely that of adjusting POA/POI elevation relationships at a specific zeroing range for a specific corresponding "range setting" on the rear sight bar and for a specific ammunition ... Period !
Thus ... let's say you decide you want to zero your Lux, FS, Trainer, or UL at a distance of 50 yards using, say, CCI Standard Velocity, and for the "sight picture" you prefer ... whether it be "Centre-Hold" or "6 O'clock hold".
Set the rear sight at the 50 mark on the range bar. Using the exact sight picture/aiming point you prefer, fire 3 ~ 5 perfectly aimed shots. If the POI's are above the POA then loosen the front sight set screw and move the front sight rearwards. If the POI's are below the POA then move the front sight forward.
The amount to move ... ?
On the Lux, Trainer and FS models, one division on the FS ramp scale will move the POA approximately 0.6" up or down respectively.
On the UltraLux variant, one division on the FS ramp scale will move the POA up or down 0.46"
For lateral deviations of the POA, a similar correction is made using the two screws that locate the rear sight blade. For the Lux, Trainer and FS models, a single turn of these two screws will move the POA a distance of 2.0" laterally at 50 yards.
for the UltraLux, A single turn of the screws will move the POA 1.53" at the 50 yard range.
Given those specifics you can easily derive the proportional amounts each "FS Division" ... or Rear Sight "Single screw Turn" will make to the POA at any desired zeroing distance.
Your sights will now be properly zeroed for that specific distance and somewhat close(?) at all other settings of the RS range bar for that specific ammo ... BUT Not Exact !
As for the poi change it is easy math
50yds is 1800 inches. using a sight radius of 20" here is the answer 20 Divide by 1800 = .011" to move the poi 1" .022" for 2" and so on.
Quite basic .
I hope this helps.
R
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Not knowing when I might get the #2 and #3 sight posts from CZ I decided to modify my #1 post. Using the sight correction from the Brownells calculator I figured something around a 1/16" would be close. I tapered the post a bit and put a shallow groove in the top to center a little brass brad which I then soldered in place. The back end of the brad I cut off about a 32nd out from the back side of the post and faired the front to the profile of the post. A bit of fairing on the sides and now I have a little brass dot about 3/64th in diameter to center in the J&P peep site.
Probably more by luck than design it is just the right height to zero at 50 yards with the tangent sight set at 50 and the front post about 2/3 the up the ramp. That's using CCI Mini-Mags.
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Nice modification. Got any pics of the finished product?
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I'd like to see it too.
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Here it is.
(http://i926.photobucket.com/albums/ad107/JBC353/DSCN1095.jpg) (http://s926.photobucket.com/user/JBC353/media/DSCN1095.jpg.html)
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That looks good.
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^^^^^^^^^^^^^^^^^^^^^^^
Yes it does!
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Thanks, it works fairly well. I may yet break down and get the Williams peep sight if only for the ease of adjustment.