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Post # 9: The Pump RP Valve: Questions Answered

10/3/2014

10 Comments

 
Our Pump RP valve for the 13xx family of Crosman air guns has been very popular due to its performance and the fact that it is Plug & Play (meaning that it simply replaces the stock valve and does not require a flat top adjustable piston).  

Feedback from many dozens of customers has been 100% positive.  Only two were ever returned: one was due to an alignment issue with the threaded hole not exactly 180 degrees from the exhaust port.  Easy fix! The other had a tiny spec of swarf at the check valve.  Another easy fix.

BUT... there is barely a day that goes by that I do not get questioned by prospective owners because they haven't read this blog I am typing now!  LOL 

Lets start at the beginning. I maintain that the longstanding fully modded flat top valve and its companion flat top adjustable piston is not one mod, but actually two.  The flat top of the valve and the mating flat top of the piston has NOTHING to do with the power potential of the valve.  The flat topping business is ALL ABOUT making the physical pumping efficiency so that a user can get more air per stroke into the valve.  Not a bad thing at all, but it does require BOTH parts (more expense and adjustment required) to get it.  I make, sell and use the flat top pair when I want BOTH more efficient pumping and a valve with more power potential.

So what if one were to take a bone stock (un-modded) valve and flat top the face of it... then pair it with a flat top adjustable piston?  What would we have?  It will take less pumps to reach the "sweet spot" (please read earlier blog)... but it will shoot the EXACT SAME fps as the stock valve and piston that took more pumps to reach the sweet spot,  The flat top is for pumping efficiency but does nothing to make the valve ultimately more powerful. So we would have to pump less to get the maximum power from the stock valve, but the performance would not be enhanced at all. 

Let's go the RP direction.  What if we leave the piston stock, then take a bone stock valve and modify it to make the pressure chamber slightly larger in volume... and then make the exhaust chamber slightly larger in volume AND angle the port?  Now the pressure chamber will hold more volume of air.  It will take MORE pumps to bring that larger volume of air even to the same maximum PSI as before the valve was modified, but now when we reach the "sweet spot" ... stop pumping and fire the gun... a larger (and more powerful) volume of air can be released from that larger pressure chamber and exhaust a larger charge to the barrel port for higher fps (and fpe).  Yes, we had to pump more times, but we get more powerful performance results.

We (and our customer users) have proven that this works very well, costs less, and is easier to accomplish. 

Other than having to pump more times to reach the sweet spot, is there any downside to this?  Maybe, depending on the operator.  If someone pumps 20+ times every time they fire... and pumps quickly,,, and shoots many times and often,,, then the stock plastic piston with its rubber cup is going to wear quicker.  I have not seen one break.  I have not even been able to wear out a piston cup yet.  But lets say that this speed demon that shoots an entire tin of pellets every outing... and shoots every time they get a chance... experiences a negative change in the gun's performance after many weeks/months/years (who knows?). What is the downside?  Another new stock piston and cup is cheap and easy to replace.  The valve, tube and linkage should be fine.  

Bottom line for me: I have a couple of guns with this valve and I like what it does for me with the way I shoot.  If I am plinking or target shooting (90% of the time) I do not pump for maximum velocity. If I am shooting for power / speed then I know I have that capability.  When I do pump that many times I do not fiendishly pump because I am not racing to shoot again and I can feel how warm the tube gets when I have done that in the past.    

For some actual chrony data from one of my customers that has two of these (one in a 1322 and the other in a 1377), please see the "Kind Words" page and the long entry there.

Just remember to "Have Fun Shooting"!

David G.
10 Comments
Joe Scuderi (4bluiiis2)
2/26/2017 12:13:30 pm

What about this RP valve + BOSS Buddy Seal transfer port in 2240 vs the Power adjuster? Or can all be used together?

Reply
David Grimes
2/26/2017 01:26:07 pm

In the CO2 22xx platform, certainly a power adjuster (adjustable hammer spring) is a good addition to the Boss RP and larger transfer port. Especially if you have a longer barrel and find that you need that valve to stay open a bit longer.

Reply
Joe Scuderi (4bluiiis2)
3/9/2017 01:46:39 pm

Thanx for advice; have and installed all of the above mentioned mods, and also a 10" barrel installed, have 12" barrel I want to install, but want to keep it a pistol not mini carbine. The 10" seems perfect for length but will try 12" later, it's only 2" longer. Still waiting to chrono.

Reply
J
3/24/2018 04:54:18 am

Crony that shit already!

Edwinwoo
6/10/2018 08:29:20 am

Dear David, i have a Crossman1322.Its new and omly shot once with a .22 pellet.Few weeks later I wanted to plink some cans but the pellet does'nt shoot out (it remain at the same position when i load the pellet).I can pump the gun, pull the trigger but the force wont push out the pellet.I have veen searching the internet gor more advice/assitance or find a solution to it.After some research (mainly from youtube), it seems it could be the valve/pump cup issue.Seems like its not retaining the pump air pressure in the valve (leaking maybe).I need more accurate assistance/advisse on what replacement parts shall I buy to get my 1322 working again.I am from Malaysia & there isnt any shop that repair airsoft.I came across your site at e.bay & I hope you can advise me what i need yo replace.Thanks.Regards, EdwinWoo.

Reply
Skeeter
10/29/2018 08:06:58 pm

One question.

If one had to guess, what is the "max" pumps for this valve before damage to the seal/poppet occurs? 20? 25?

Reply
Zachary Brown link
8/9/2020 02:31:57 am

I want to know the same thing. I have emailed him twice now about it.

Reply
Nobody Special
11/18/2019 12:36:42 pm

I purchased the full power mod kit for my 1300KT .22, vlave, hammer spring, and transfer port, and I have to say that this has transformed what was quite a nice shooting air pistol to begin with, into a rodent's worst nightmare. My standard charge is 20 pumps, and most of the time using Crosman 14.3gr hollow points, and it has become my hands down favorite plinking and rodent hunting tool in my gun safe. Thank you for making such an effective upgrade kit that is so easy to install available at such a reasonable price!

Reply
Samuel Elliott
12/18/2019 02:42:54 am

Love the RP valve. I haven’t chronyed it yet but it’s denting the back stop plate in my trap at 25 yards with 10.5 grain Magnums at 25 yards.

Reply
heatpumpservices.co.nz link
3/1/2020 11:19:23 am

The great concepts I have ever seen and getting more pump services and installation here,keep follow the blog. Mostly generating the effective techniques and following useful heat pump service.

Reply



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    Author: 
    David Grimes

    A serious airgun enthusiast with a particular fondness of Crosman pistols, I learn something almost every day.  


    I am not an overall expert or guru, but I will share some things from time to time that maybe some of you will find interesting.  


    There are often many ways to accomplish an objective. I do not pretend to either know them all or imply that I am always right. 


    Therefore, I reserve the right to be wrong from time to time.  ;) 

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