Increasing velocity on a 1300KT

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fishinwrench

fishinwrench

Member
Nov 25, 2017
589
16
mo
I have this little darling... 
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And I'd like to get it shooting closer to 11-12fpe. It is currently shooting at about 9.5 fpe (545fps with 14.3gr.) with 12 pumps.

Here is the catch though ....I don't wanna pump it more than 12 times. So is there anything I can do to boost velocity without having to add more pumps ?

Will simply adding a larger TP help?

Heavier spring?

Since it is obviously already dumping all of the available air I am wondering if dumping the available air FASTER will boost my velocity ? Does that even make sense? 

🤔

I have a basically stock shorter barreled 1322 that actually shoots faster than this gun ....so that tells me that there IS a way.
 
Fishingwrench, Head over to eBay. You want a custom flat top ported HP valve for crosman 1377, 1322 pc77. $27.88. seller is (needfulthings) aka Alchemyairwerks. Hope this help.
Click to expand...

Ok I'll go get it. I will need a flat face piston also, right ?

Will this up my velocity with the same number of pumps?

I already have a BOSS TP for this gun but haven't installed it yet.
 
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Yes on the flat top piston. You could flat top your valve if you have a drill press. A heavier hammer spring and a lighter check valve spring. Oh how did the PRod turn out

With a.flat top valve/piston it will be like this. 6pumps will be like 10 pumps , 10 pumps will be like 15 pumps 12 pumps would be like I dunno 20 pumps. The set up is more efficient, creates more pressure per pump. A mod I used to do is, open the valve and cut off 3-4 male threads to increase the volume of the valve more air behind the pellet
 
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The transfer port is another spot to look at. And also the bolt. I've used a drill press to turn the probe way down and the replace the oring with a slightly bigger one, lol the oring out of a bic lighter was the magic mod some decades ago... you can just put extended probe into Google polishing the tube the hammer rides in will also give you a small bump

Oh yeah look for an adjustable piston I got a valve and piston kit once that was not adjustable, didn't fit the stroke. But that was a long time ago

You may want to check out Gunslicker tutorials on YouTube. That dude does it old school. AirGunNirvana is another old DIYer on the tube
 
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