My Hatsan AT-44 .22cal Huma regulated tune.

[blackdiesel]

No vocal instructions but visuals:

[Masochisti]

No vocal instructions but visuals:

Thanks! "Hastan at-44" 

[Masochisti]

Disassembling this gun seems easy for the main parts! Only problem is that I can't get the transfer port out... It simply wont budge! Nothing should be holding it back unless it has welded itself to the valve port... 

[hotshot]

Use an appropriately sized allen key and lever it out from inside the brass housing that the valve screws into.

[Masochisti]

Use an appropriately sized allen key and lever it out from inside the brass housing that the valve screws into.

Already tried that, no help. Going to tap it tomorrow lightly with a small plastic hammer and see if it would give in just a bit and then push it out.

[hotshot]

Mine was farly tight and took a bit of force to get it out the first time, but that sounds ridiculous!

You could try the lever method again using a short screw inside the transfer port with a head size close to the size of the hole in the brass housing to spread the force evenly and thereby get more purchase on it, perhaps?

[SpiralGroove]

Masochist,
Mine wouldn't come out either.  I destroyed it getting to come out, like pulling a tooth.  Since I have a lathe, just made another.  Good Luck ............ that one really got me ticked

Most likely loctited in, heat it up using a soldering iron for few minutes, she may just pop out!

Kirk

[Masochisti]

Ok no luck. Its tight...

Well I ended up taking the trigger and safety away > that gave me access to the hammer spring

[Masochisti]

So I finally got my hands to that "dang" hammer spring... I think I'm heading the right way 



Did 55 shots. From 200 bar to 100 bar. Used Crossman Premier Pointed (14.3gr).

I only took out the round end cap at the end of the spring (inside the hammer, approx 3mm thick?). I think it does have some kind of purpose there so I need to replace it with with something else. Also checked how the top valve hole lined up with the transfer port hole... its a bit off sadly. So before I go plugging those bottom holes I need to find a way to line up top hole with tp.

What a great gun to work with.

[SpiralGroove]

Looks much better

What size are your ports: Valve, Transfer & Barrel.  They should be between 5/32" and 11/64".
Plug the remaining valve holes except one, use JB Weld.  Shim or trim the valve a few thousands and it likely will line up with the TP.

Make sure you're on the Knee of the velocity curve, using the RVA.   
 
Your shot string will extend to 60, 55 strong shots.

Good work 

[Masochisti]

What size are your ports: Valve, Transfer & Barrel.  They should be between 5/32" and 11/64".

Haven't measured them yet. I've misplaced my caliper, gotta lend one from work tomorrow and check them.

Make sure you're on the Knee of the velocity curve, using the RVA.   
 

So I will turn the hammer force down until I get some serious drop in velocity and then tune it up a little to get back > thus meaning I will get better efficiency. (?)
Whats RVA? 

Thanks again!

[SpiralGroove]

- Use drill bit ends to estimate port sizes.
- You are right on about the knee - about 20 to 25 fps below top velocity).
- RVA (sorry) - Rear Velocity Adjustment (or hammer pre-load).

Good Luck ................

[Masochisti]

More work on the gun!
Plugged 3 lower holes on the valve with JB. Adjusted the regulator from 110bars to 100bar. Decided to cut the hammer spring 8mm shorter and added the spacer back into hammer (4mm thick). Adjusted hammer spring 2 turns CCW (getting 790-800fps with 14.3gr which is good for me).

Had 0.77g (11.9gr) RWS pellets laying around so decided to do a chrono with them. From 200 bars to ~90 bar.



Pretty happy with the results 

I did some shooting with earlier settings with CP pointed 14.3gr and at 50m I get 1" groups constanly even with some wind. Getting some JSB 16gr soon, I bet they shoot even better...

[Monkeydad1969]

Wow, Matti...nice strings.

[Masochisti]

Small update. Not too much work on the gun lately (busy busy...)
Right now it is regulated at 145 bars and it shoots JSB 16gr @ 880fps. I can get 30 usable shots from 200 to 140 bar. Did some shooting (was bit windy though... darn) yesterday and I'm quite happy. All shots done at 50meters. JSB 18gr group quite nicely too. For some reason my rifle does not like JSB Monsters at all. It swings those 25 grainers all over the place.

30 shots, 6 x 5 shot groups, 5.50mm, 5.51mm and 5.52mm. Few flyers but I'm to blame not the gun... 

[Masochisti]

I plugged all of the valve holes and opened one (the one that lines up best with transfer port) to 4.2mm. Im getting 50 solid shots with 15.98gr JSB:s @ 840fps. Regulator set at around 125-130bar. I think that this is pretty good result (180cc) and leave it where it is. I decided to use last of the RWS 12gr pellets in the middle, thus the "bumb" in the string.



Also I tested my old camera with a scope mount to record some shots done (2 months ago with old tune settings and cheap chinese 6-24x scope, got new scope coming now). Black background and better light would work better to see the pellets flying but meh... just a test so far.

[MicErs]

I should have read the whole thread before I posted this link:

http://www.gatewaytoairguns.org/GTA/index.php?topic=74919.0

[Masochisti]

I should have read the whole thread before I posted this link:

http://www.gatewaytoairguns.org/GTA/index.php?topic=74919.0

I've been reading rsternes posts and value them highly. Great info and help!