Canadian Airgun Forum

Someone posted that a 1389 could be turned into a 2289 fairly easily so I decided to try it tonight. Didn't do much to it mod-wise except a lighter valve spring and chopped the fibre valve seal (right word??) in half to give a little more volume. Left the port as original.

Gave me 370 at 10 pumps and 408 at 20 with 14.3's. This has a lot of possibilities as I figure I should be able to hit a little over 400 at 10 pumps with a porting job. Anybody else done this??? All info greatfully accepted

Cheers - Gus

i guess a metal piston rod helps a lot. not sure if you get a more efficient pump with either the stock pump cup, or a custom flat metal piston with an o-ring. i got a good power increase with that mod alone. that and a porting job will probably get you right close to 500 fps. check to see if theres a bleed hole in the back of the valve. if there is, fill it before you do anything else. see what happens.

Do a search for my sniper project post. I've found that with the 2289 the secret is to DECREASE valve volume. A larger valve with CO2 is advantageous, because A: there is a surplus of gas, and B: it is a constant pressure.
With a pumper you have to build the pressure, and the fastest way to reach higher pressures is to have a smaller valve volume. The amount of air in said valve is secondary (within reason) due to the short barrel.

I am up over 600 FPS at ten pumps.....shooting 21.6 grainers!

Lots of good info on modding these things, just do a search.



Ryan

i tried that with my 1377. i did big volume, and that was crazy. i can throw 100 pumps into it and shoot ravens 80 yards away. when i tried to reduce volume, sure it reduced the amount of pumps to max pressure, but i lost a lot of velocity. if you go less volume with higher pressure, you need a piston that will tolerate that high pressure... also, think of pump headspace, the reason your valve stops taking in air, is that the air your compressing as you pump, is being compressed, but theres room for it to stay on the outside of the valve, know what i mean?

so... to achieve higher pressures, you need to eliminate as much headspace as possible, and figure out a piston that can withstand high pressures. otherwise, it'll just blow right back out.