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Converting a CZ200S to a CZ200T

June 16 2017 at 10:38 PM
Brazos  (Login Brazos2)
YF12

I have some CZ200S models and I want to convert one of them to a T model for 10M. I have the sights. What I want to know is if there is any trick to reducing the power down to 10M levels? I know there are some hurdles to take a T to an S. I assume I just reduce the hammer spring pressure until I get to the desired fps and then tinker with the strangle screw on the side of the receiver to fine tune. Just want to make sure I don't need a different/lighter hammer spring or something. This is a new S model about a year old. Thanks.

 
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Bruce Scott
(Login Bruce.net)
YF12

CZ Conversion

June 17 2017, 8:11 AM 

I had a few of the CZ/S models a year or so ago. I found that the strange screw had a greater effect on velocity vs. the hammer spring. The hammer spring should give you the small fine tuning adjustments.

Obviously altering the spring would give you a big change as well.

The PA website used to contain instructions for going the other direction. That might be worth a read as well.

Good luck with your project. They are a great platform.

Bruce

 
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mot
(Login critter99)
YF12

target model

June 17 2017, 8:29 AM 

From the factory the the low power target model has a smaller barrel transfer port. The tranfer port adjustment screw will easily get you down to 11fpe. Not sure it will get you all the way down to 7 FPE like the T model

 
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gubb33ps
(Login gubb33ps)
YF

Try the strangle screw first.

June 17 2017, 10:14 AM 



Can "almost" help you.

Have a .177 200T. This U.S. version is marked AA 200T and is marked 16J.
Have a .22 AA s200. It's also marked at 16J.

Everything on the inside (spring/striker/air passages) is identical.

There are other versions (more common outside the U.S. (but here as well) that were marked at lower energy (7.5J?) that do have internal differences.

So I'm going to assume the one in your hands is the US version of the 200T that is marked 16J (normally on the right side of the reciever, where the barrel connects).

Assuming you have the 16J marked version, I'd try that "strangle screw" (which is actually a air flow restrictor screw for the transfer passage).

Think of it this way: the striker spring adjustment sets the range of pressure that the rifle runs best in....the strangle screw sets the amount of air reaching the pellet.

On the 200T at hand, have it set for a nice shot count at 12 foot pounds. BY just turning the restrictor screw in, will shoot at 7 foot pounds (and a longer shot count).

Works over the same fill pressure rnge (the striker spring adjustment isn't changed), just either letting more air reach the pellet.

Your post shows you DO NOT have one of the other versions, but will mention them anyway.

Some were/are made for places with more paranoid/restrictive air gun rules, that were made non-adjustable ("tamper proof"). On the ones I've seen, they didn't slot the striker spring adjustment, glued it in place, and either never drilled for the air restriction screw or rivited over the hole.

 
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Bob D.
(Login MB-BOB)
YF

The difference between the 200s and the target 200T...

June 17 2017, 11:36 AM 

is the diameter of the transfer port milled into the receiver. IIRC correctly, the 16J rifles have 2.5mm TPs, while the 7.5J rifle measures only 1.5mm.

The reason for the smaller TP is so the 7.5J rifle can complete 60-shot matches (plus multiple sighters) on a single cylinder, in its un-regulated velocity sweet spot, using the 7.4gr (avg) wadcutter pellets used in paper-punching, 10m Int'l matches.

As others have mentioned, you can de-tune the 16J model to approach the 7.5J model's velocity, using the heavier, round nose pellets easily enough. But for actual 10m Int'l matches, you will be required to use the wadcutter pellets. However, using such lightweight pellets will only increase the velocity you've worked to reduce, and increase air consumption due to the less mass of the lighter pellet. Probably doable, but you will have to work at it.

The standard strangle screw on the rifle has a conical shape. You might try a replacement set screw, with a rounded shape to match the back wall profile of the 2.5mm Transfer port. Essentially, you are trying to strangle the TP to almost no air passage, then back off as needed to build the minimal pressure needed.
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This message has been edited by MB-BOB on Jun 17, 2017 11:39 AM


 
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Jeff D
(Login jcdx25)
YC

If if comes down to style (wadcutter) and weight... search...

June 17 2017, 1:45 PM 

Mid 7's gr wads may be the avg but at 10m power levels (or close) a grain matters.

My dedicated 10m stuff (a Steyr pistol and an FWB rifle) like Meisterkugeln 8.2's the best. There are several other wads out there in the low-mid 8's. and the RWS Supermags (9.3gr) are as good as the JSB 10.3's in my higher power rifles (at 20y and less) but diff poi so only shoot them for offhand practice with those rifles, on a 10m target now...

I've had a CZ200 down to about 9.5fpe. Below that got erratic with shot to shot variances.
I purchased a replacement tube with quick fill and reg for the one I have now, it's at 10.5 fpe. I could have specified that the reg be set to any level. I've not been in to adjust it but might in a few weeks. I think I want another 25-50 FPS out of it.

 
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gubb33ps
(Login gubb33ps)
YF

Needed a quick project...

June 17 2017, 1:29 PM 

..so I'll go out and see how far down it will go.

Has been set "forever" at 12 foot pounds (11.8)...about time I see just how a well broken in 200T (16J) can slow-shoot and still keep consistent velocities. Although I don't have any appropriate wad cutters at hand, can make a pretty educated guess from what 7.3gr. JSB's that I do have on hand.


Likely take about an hour.


    
This message has been edited by gubb33ps on Jun 17, 2017 1:30 PM


 
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gubb33ps
(Login gubb33ps)
YF

results

June 17 2017, 3:25 PM 

Well...it can certainly go slow enough.

Change of plans : I'm short of 7.3's but have a large supply of 8.4's.

.177 200T ifle would be the one-piece stock (newer) version of on top. The old 2-piece stock is a .22 s200.

photo 441fa67c-0166-43b2-a61c-cd7d206536a1.jpg

Also..no adjustable butt or cheek on these basic models.

1.Did not take off the scope and mount match sights or remove the LDC's.
2.Know where the "sweetest of the sweet" spot lives in this rifle (about 155-110BAR), the area most likely to produce the smallest velocity spreads (1 to 2%).

3.Filled it to 155 bar for each of the tests. Really hardly any effort as so little air was used to fire 12 shots at these speeds

4."Dumped" two shots into the a dirt pile just to let the rifle get use to the idea of a new setting.

5.Chronographed 10 shots.

6.Refill to 155BAr for each and repeat #3-#5.



Ran the screw all the way in until it stopped (but did not tighten it up like it was a scope mount..just barely feeling the end of the line).

Added turns in fractions.

Then put it close to where it lives its 12 foot pound life (although a little faster than it was...need to back it back down a fraction of a turn).

photo f17c501a-8b2f-497d-b27e-edac08fa3831.jpg


As for "why" some settings are pretty crappy in vel. variations and others much better...really haven't a clue. Might be the small test number...but it seems more than that is going on.

Ehh...rifles are picky.

You'd be on your own for figuring out shot counts, efficiency, vel. variation you can live with, pellet selection (although there are some very nice 8.1-8.2 WC pellets), etc.

But at least this one (which is abut as box-stock as it gets) can make the speed limits.

OK...at the first shot at the "0" setting (the "dump in the dirt" shots), I thought it didn't shoot at all. SAW the pellet hit the dirt pile, so I knew it did shoot, but with that LDC still attached, I really had initial doubts that it fired at all or was shooting so slow the chronograph would refuse to read it.

Hope it helped a little....made for an interresting mini-project for me.


    
This message has been edited by gubb33ps on Jun 17, 2017 3:30 PM


 
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Brazos
(Login Brazos2)
YF12

Thanks

June 17 2017, 8:41 PM 

Thanks everyone for all you suggestions and efforts. I will start with the strangle screw and see if that gets me there. If not I will find a longer screw as DFW Dude suggests. My 12 year old daughter is enrolled at an air rifle camp at the high school in July. They have a very good rifle team there. I am hoping she will enjoy it (you know how that goes). I want to get this spare rifle set up for her in advance so she can at least shoot a rifle with target sights before she goes. I had been contemplating setting this rifle up for 10M anyway so I might as well do it.

 
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