.22 Cal Marauder fps are too low

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kk4iz

Member
Oct 17, 2015
322
2
Alabama
We would like to up the fps to around 900 fps I think, right now avg fps is 826 with18.13 JSB but only 10 shots before it drops off the regulator (Huma) set at 135 bar. 
Just started playing with it, I did turn the reg. up from 120 to 135 bar to get more fps but did get much of an increase but lost shot count. We replaced the barrel with a Marmot Militia barrel and installed a Huma reg... What else can we replace to improve the gun and get fps up ???
The gun is shooting a good group at 50 yds. dime size. Almost as good as my wildcat .25. But no where as many shots per fill.
Thanks ahead

KK4IZ 
Warren
 
It is an anti-ping hammer design which makes it to where the hammer hitting the valve (which releases the air to propel the pellet) only strikes once, instead of bouncing multiple times (even after the pellet has left the bore). The hammer bouncing wastes air, so the SSG enhances the number of shots you can get by making the hammer strike on the valve more clean (ideally a single strike). Even with the SSG, there is some tuning required to get the best overall effect.
 
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You have something out of whack in the tune. With the reg set at 135 bar you should be able to easily get over 30 shots. I got 34 out of my S510 carbine that has a shorter barrel and smaller cylinder set at 137 bar with 18 gr. JSB @ 835 - 840 fps. Theres a good chance you have the hammer hitting with to much energy causing the valve to stay open well after the pellet leaves the barrel. What do you have the settings at for Hammer Spring and Hammer Travel?
 
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we will get back at tuning later this week. we have been at the doctor's office every day this week and got 2 more days of it. Just what happen when you make it over 67, I thank the doctor are trying to put me under instead of keeping me above ground. 
Does anyone make a better value than the Marauder value. We have drilled the port hole out a few thousands our also the transfer port. 
 
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The marauder valve is fine for a regulated .22 Mrod. You need to tune it over a chronograph and get it tuned to the knee. My guess is you are way up on the plateau and thats why you have horrible efficiency. Just to much hammer energy for the lower pressure the valve is seeing after being regulated. So basically the hammer hits the valve opening it but holds it open longer than needed just dumping air.
 
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 Why the magic "900fps"? You say it groups well and shot placement is what counts if hunting/varmiting.

And you say MM barrel, haven't owned one but most who use them and post say the bore is tight! You are likely loosing some fps there ( and most seem to need frequent cleaning for best results. In .22 ( first hand exp. here) a tight choke can take a full 40fps off the top end, perhaps more? Still have the factory barrel? You might check fps with it installed. An LW poly barrel would likely shoot slightly higher fps, not that you'd want to change at this point but it could be a small part of fps.
Sounds like you have some good clean tinkering fun ahead.

It looks like hills airgun again has marauder valves ready , Don Cothran seems to make the most powerful marauder valve though you'll need to know what your
doing and may need light mod to rifle (?) such as transfer port, other . His valve is mo0re for bog-bore conversions - might have other sets ups?- and can make close to 300fpe. And I know there is at least one more I cant think of right now. 

If two weeks is the amount of time to get a custom part in your hands, that's pretty darn good really. If they are say, making another run of parts in two weeks and unknown date that's different.

John


 
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