GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: NWAForester on November 12, 2014, 10:32:57 PM
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So, I recently got a Galatian .25 QE, and promptly decided to go big or go home.
The gun was PHENOMENAL out of the box, but coming from a family of network, telephony, and structural engineers, architects, etc, i just can't leave well enough alone on anything, lol
First step, I had Hatsan upgrade to a full length barrel and shroud. Unfortunately, the new, longer shroud is not the glossy finish like the stock shroud, and its also slimmer before the moderator. Not as nice looking, but I think a can of glossy black enamel will fix that. The longer barrel alone adds about 100fps.
Then I went to town.
Starting in the air cylinder.
In the black cap that holds the valve spring in, I drilled the holes out the 7 holes as large as i could without losing too much strength, the even chamfered the holes.
I took the valve needle and thinned it down using a table grinder. Not the most accurate job, but it worked. Took a little more off than intended,lol, but seems to be holding well.
Also, opened up the derlin seal a step too.
Drilled out the exhaust port on the valve too. Haven't gotten around to closing the others yet.
The transfer ports in the receiver are already pretty large, and making those any lager would take a larger screw to hold in the brass sleeve the cylinder screws into, so I haven't bothered messing with that. Though that screw hole lines up perfectly...... ;)
Then turned the hammer spring up as much as possible without causing cocking issues.
I got 992 FPS peak and an average of 975ish over a 13 round clip with the Kodiak 31.02 grain. And thats a full clip at pretty much full power.
I was hoping to get about 80ft/lbs, but don't think i can quite make it that far. Though I have seen it out of a BT65.
Not to bad for some pretty simple tweaks, but I don't think 80 is quite possible, but I think 70+ is doable.
Just out of curiosity, any one have numbers to show how much blocking the exhaust ports alone improved power?
Any other tips on getting a little more out a Galatian?
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I only have that information on an AT44.... Blocking the ports reduces the power but improves the efficiency.... Blocking the lower 3 ports lost about 15 fps.... blocking the bottom 5 ports lost about another 100 fps (a total of 115) but drilling the remaining top port out to ~75% of the caliber gained all of that back... The most efficient setup was with the 5 lower ports blocked and the top port matching the size of the transfer and barrel ports at ~75% of the caliber.... My .25 cal AT-44S Long did 61.5 FPE with Kings, 65.4 FPE with 'Cudas, 73.4 FPE with EunJin Domes and 78.4 FPE with EJ Points.... Ports ran 0.182" to 0.187" equivalvent areas, including the throat....
Bob
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Here is Bob's whole thread on the AT44 Long he is referring to.
http://www.gatewaytoairguns.org/GTA/index.php?topic=33903.20 (http://www.gatewaytoairguns.org/GTA/index.php?topic=33903.20)
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this thread not worthy without pics!
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Forester, do you have any info on tuning the bt65.?