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Mark5043 · Silver Status Member

I was able to run my new 1322 over the chrony today,after installing a 14.5' barrel,and a hammer spring from a Discovery.To be honest,I'm not really impressed with the numbers...

The test is by no means scientific,I was just trying to establish a baseline performance.I'm looking to mod this gun further,and am looking for the most out of it.I intend to keep the 14.5 barrel,as this will be a backpack gun.So far I've taken three shots at each power level,starting at three pumps,and finishing at twenty.The averages were then calculated.I've noticed the gun peaks in performance gains at fifteen pumps.There are gains after that,but they are minimal at best,so not worth the extra pumping effort in my opinion.

Next up for mods,I'll be installing a metal breech from a Discovery.I like the idea of that metal barrel sleeve for extra barrel stability.I will have to pull out a #42 bit,and a 4-48 tap to make it work,as the new 1322 main tubes only have one hole ,and that is for the new screw location.Not a big deal.

So...a couple of questions for the power junkies out there.As this rig will be for hunting,I'm hoping to get 600-650 Fps,with the "14.5 barrel",and14.3 Gr. pellet.Looks like I need to get a flat top valve,and piston set up for openers.I've heard of 100fps gains?Is this with the .22 cal as well?What are some of the little tricks you guys have done to develop additional power with these pumpers,and does anybody have numbers to show how much each mod improves performance?

rsterne · Moderator

Basically, you`ve made a 2289.... With a F-T-P they get about 500 in 9 pumps and 600ish in 15-16 without any other mods.... If you streamline the valve, drill out the ports, and put the sear spring in the valve (when you fit a lighter trigger spring) you will pick up 30-40 fps more.... The Disco spring won`t buy you any performance if the gun isn`t retaining air (a dump is a dump).... but it will allow you to pump more before that happens.... If you preload the Disco hammer spring and fit a lighter valve spring also.... you may have to cock the gun to pump it.... 750 fps is possible at about 30 pumps with all the mods done.... more than that requires a longer barrel....

Bob

Mark5043 · Silver Status Member

Thanks Bob for getting back to me.750 fps power potential?...really? Shocked

That would be nice to have that kind of power,for certain occasions.
I wasn't aware that one can use the stock sear spring,in place of the existing valve spring.By streamlining the valve are you talking about opening up that right angle down in the exhaust port to say 115 degrees or so?

Also,I've contemplated increasing the valve volume,like one would in a 22XX valve....but I have second thoughts about it.It seems to me that increasing the volume of a 1377/22 valve would just increase the amount of pumps needed,and require,an even stronger hammer spring,and or lighter valve spring to get a full dump?

Last but not least..transfer ports.I don't really want to go the poly tube route,so I don't want to enlarge the the recesses in the barrel or the valve."If I had a lathe to turn some custom TP's,that would be a different story"For now I'm interested in carefully increasing the ID of the stock port.I remember correctly you mentioned in one of your threads,various TP sizes,and what effect they had,but can't find it.Obviously I could only enlarge the ID of the stock port so much,as there isn't much metal there,to play with.So based on the testing you have done on TP's thus far,what would you consider ideal for my application?

rsterne · Moderator

I angle the valve exhaust port 20 degrees (110 included angle) with a 1/8" mill and then grind by hand to smooth and round the bottom corner.... In .22 cal you don't need to worry much about the extra TP volume, the flow seems more important.... The poly port works fine, I drill my steel ones to 0.161" and the barrel port to 0.166" and try and get the valve to flow at least 5/32" right through....

RE valve volume, it all depends on what you want.... For low pump numbers, restricting the volume pays dividends.... For high pump numbers, the extra volume helps.... On a 2289 in the 600-750 fps range I would leave the valve volume stock.... The hammer strike required is more related to pressure than volume.... A larger valve will actually dump easier with a given number of pumps as the internal pressure is less.... just like with a 140 the trigger pull is less....

Bob

Mark5043 · Silver Status Member

Okay Bob,now I'm understanding things a bit better.For now,I've only got a Dremel set up to work with.So I might wait until I have a spare valve,in case I F it up,on the first try.I guess the main concern would be taking too much off that bottom corner,and enlarging where the valve stem seats,causing a leak.I doubt It's that hard,since I have ported RC car engines with a Dremel before,and had excellent results.

rsterne · Moderator

Yeah, just be careful of the sealing surface and you'll be OK....

Bob