Author Topic: Hatsan AT44 .177 tuning  (Read 188 times)

mcoulter

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Hatsan AT44 .177 tuning
« on: October 11, 2019, 12:20:15 PM »
I bought a used AT44 in .177 recently.  It was a great deal and caught my eye since it came with two air cylinders.  One was standard and the other was regulated. This has been an enjoyable platform to play with. 

Here is my latest "tune".  I'm quoting tune here because I'm really just playing now...  Other life responsibilities have kept my trigger time down so this was a somewhat hurried shooting session.

Pellet .177 JSB Monsters 13.4 grain (original)
Hammer spring = about 3.25 turns out
Regulator = 110 bar (probably - need to further test to confirm)
Starting / ending pressure = 200 bar / 100 bar (notice hiss of valve leak after string)

Avg fps = 778 (18 fpe)
Max fps = 787
Min fps = 770
ES = 13 fps
ES% = 1.64
Number of shots = 40

I'm super-happy with the consistency but I'd love to move towards a higher velocity.  My Flash shoots the monsters at about 22 or 23 FPE and is more accurate than the AT44 currently is at 50+ yards.  It's Robert Lane regulator that's in there so I'm planning to go through the techniques mapped out here as time permits!

/>
I'm hopeful that I've fixed the air leak from the valve, but I guess that I won't know for sure until after I shoot it down again. 




« Last Edit: October 11, 2019, 12:23:40 PM by mcoulter »


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Alan

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Re: Hatsan AT44 .177 tuning
« Reply #1 on: October 11, 2019, 01:11:40 PM »
Patience, they say, is a virtue. Apparently, you have it! I do not!
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Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.

mcoulter

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Re: Hatsan AT44 .177 tuning
« Reply #2 on: October 12, 2019, 04:50:14 PM »
OK, I spent a good amount of time playing with the AT44 and it's leaky valve.  I tried adding some preload (a spacer) behind the valve spring for a while while shooting and that extra pressure may have helped it seat better.  I have since removed it and the leak still seems to be gone.  (The leak seemed to occur when the air pressure was low(ish) at less than 120b. 

Anyhow, my last string was at a higher hammer spring tension than before (4.5 turns vs 3.5 or so).  The regulator set pressure seems to be about 120 bar.

I did three tests -

1) A typical fill it up and shoot it down




2) A test I saw on the Lane videos where you shoot a few shots at low pressure (I started at 70 bar) and increment it up taking a few shots at each pressure (I went in 10 bar increments even though he said to do 5 bar increments) until to you go over the reg pressure. 



3) A hammer spring tension test - I started at 0 turns out (after screwing the hammer spring all the way in) and then shot a few pellets at full-turn increments out to 7 turns.  (Ignore the title on the chart... copy/paste error)




That spike at the end of the shot string is consistent with one of the Lane Videos.  His recommendation is to turn the regulator DOWN to deal with that. 

/>
I may try that but first I'll check my hammer spring.  After turning it quite a bit, it does feel loose.  Have seen it "walk" on its own.  I'll put another light streaking of vibratite on it if its any different from what it was last set at (4.5 turns out).  I will likely put it back to about 3.5 or 4.

To be continued! 
« Last Edit: October 12, 2019, 04:55:48 PM by mcoulter »
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UCChris

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Re: Hatsan AT44 .177 tuning
« Reply #3 on: October 12, 2019, 07:17:09 PM »
Excited to follow this. I will be regulating a Flash to 12 fpe. Kinda going the opposite direction of you.

mcoulter

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Re: Hatsan AT44 .177 tuning
« Reply #4 on: October 16, 2019, 05:01:07 PM »
Excited to follow this. I will be regulating a Flash to 12 fpe. Kinda going the opposite direction of you.

Thanks UCChris!  Unfortunately I was not able to shoot any more last weekend after making the above post.  I hope to "play" more this coming weekend.  After that I will be running through the same process with the unregulated tube.  Being a used gun I'm not exactly sure what was done with or too it and I'm still rather surprised that it's not shooting "hotter". 

It's all good though.  I'm really enjoying the stuff I'm learning with it  :-)
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UCChris

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Re: Hatsan AT44 .177 tuning
« Reply #5 on: October 16, 2019, 07:54:55 PM »
Excited to follow this. I will be regulating a Flash to 12 fpe. Kinda going the opposite direction of you.

Thanks UCChris!  Unfortunately I was not able to shoot any more last weekend after making the above post.  I hope to "play" more this coming weekend.  After that I will be running through the same process with the unregulated tube.  Being a used gun I'm not exactly sure what was done with or too it and I'm still rather surprised that it's not shooting "hotter". 

It's all good though.  I'm really enjoying the stuff I'm learning with it  :-)

You've done stuff since the fill up and shoot down graph right? If you increase hammer spring tension just little, then I would expect your regulated shots to go up by 10 or so fps, then the spike at the end of the regulator will be less. No reason you can't keep it all in the 2-3% range, at the expense of a couple less shots, of course.

mcoulter

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Re: Hatsan AT44 .177 tuning
« Reply #6 on: October 19, 2019, 06:18:54 PM »
I did some shooting today and took a slightly different track.  I decided to lower the reg per instructions on the Lane videos.  My best guess is that the reg is now around 100 bar (+/- 5 bar or so).  I got this with JSB Monsters (original):

 - 50 shots in 2% spread
 - 16.5 fpe average
 - 744 fps average
 - 15 fps extreme spread
 - 210 bar down to 92 bar fill
 - 4.5 turns out on the hammer spring

Yup, it's a steady decline and then a spike again, but I'm still pretty happy with the consistency.

https://photos.app.goo.gl/HBHZ9JCMdcmougZw8




https://photos.app.goo.gl/Nq9k4EJQ8vZhFyu56




I also shot a bit with my unregulated tube.  I kept the hammer spring at 4.5 turns:

 - 30 shots
 - 170 bar down to 112 bar
 - Extreme spread 23 fps / 2.7%
 - 20.6 fpe average / 832 fps

https://photos.app.goo.gl/xqdetkqe5Rd7JvrL9





Here is my regulator pressure/velocity test:




And it definitely liked shooting the JSB Monsters at the lower (regulated) velocity.   Here are regulated groups.  The top left is my pressure/velocity test and the rest are "normal" 10-shot groups at 32 yards:



FWIW, it also really likes crosman "magnums" 10.6 grain pellets.  I don't have the graphs, but here are some targets.  These are actually the copper magnums.  They do pretty much the same as the normal ultra magnums...  They were shooting up to about 900 fps:

« Last Edit: October 19, 2019, 06:31:14 PM by mcoulter »
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