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AT 44 Valve Stem?
https://www.airgunforum.ca/forums/topic74252.html
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Author:  custmshoot [ Sat Oct 29, 2016 12:42 pm ]
Post subject:  AT 44 Valve Stem?

Looking for a full power valve stem for the Hatsan AT 44 22? Sniper does not have any. Any suggestions? Anybody making them? Thanks Bob

Author:  Daryl [ Sat Oct 29, 2016 3:03 pm ]
Post subject:  Re: AT 44 Valve Stem?

Although not identical to the AT44 stems and being BT65 stems, the 'work' is similar. Start with a sub 500fps stem, and turn off just a tich of diameter. A lathe is prefered, however a 3/8" electric drill held in a bench vise and a fine mill bastard file will do the same work.

Image

Left is a stock, 500fps stem. Middle is a 20fpe stem with VERY slight reduction of the stem's "shank" diameter. A very little metal removed allows a LOT more air due to the pressure of a PCP.

The third is a full power stem, ie: 1,300fps or more. Note from it's shape, it is a waste of air. Something between the middle shank and third from the left, is the desired stem shape. I would think even a straight shank would waste air and perhaps deliver higher speed than useful. Try for about 900fps to 950fps.

Note the middle stem and now only a slight amount of material was removed. THUS, one removes only a tiny amount, then tests using a chronograph. The angle (shoulder) of the sealing shank must be maintained.

Author:  custmshoot [ Sat Oct 29, 2016 3:42 pm ]
Post subject:  Re: AT 44 Valve Stem?

OK, Thanks daryl. Thanks for the detailed info. Have a friend who is a machinist, so will give it a try. Bob

Author:  rsterne [ Sat Oct 29, 2016 5:24 pm ]
Post subject:  Re: AT 44 Valve Stem?

IIRC, I made my stem straight, and then set the velocity using the hammer spring preload.... That was in .25 cal....

Bob

Author:  custmshoot [ Sun Oct 30, 2016 7:53 am ]
Post subject:  Re: AT 44 Valve Stem?

Bob. Thanks for the info. I think I will try modifying the valve as I may use the cylinder on more than one rifle. Keep them in the 10 ring! Bob

Author:  Daryl [ Mon Oct 31, 2016 6:35 pm ]
Post subject:  Re: AT 44 Valve Stem?

Beautiful standard Atlantic Salmon fly, btw - too bad the picture wasn't a tich longer, to show the gut eye.

Author:  Daryl [ Sat Dec 24, 2016 2:39 pm ]
Post subject:  Re: AT 44 Valve Stem?

You could actually start here and go from there to possible links by rsterne - he is, afterall the magician with AT44's.
this was a simple search for AT44 power mods

search.php?keywords=AT44+Power&terms=all&author=rsterne&fid%5B%5D=14&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search

Each one of those has it's own thread, btw - like this one:

topic48843.html?hilit=AT44%20Mods

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