Benjamin Marauder gets a power wheel / tp adjuster
- By Stubbers
- PCP Airguns
- 5 Replies
This is not meant to be a tutorial. If you decide to attempt this mod yourself do so at your own risk.
Not that anyone really mods marauders anymore, but ya never know what kind of history will repeat itself. I have yet to see this mod done on a maraauder so I figured I'd share.
I found the stock velocity metering screw on marauders lack luster, requiring an Allen key to adjust, while being limited on how much it can restrict with large ports, I decided to add a quarter turn transfer path adjuster as many modern pcp's have. (Plus I shamelessly epoxied my VMS bore ages ago as it was the in thing to do at the time). I have another unregulated marauder that I may keep the stock OEM setup, but probably not.
The adjuster I fabricated is made from 7mm stainless steel tube with 4mm ID, opened up where it matters to .235"x.215" for a perfectly blended .225" exit port going through my valve. It's retained by a 4-40 screw and the knob is also 4-40, both of which were pressed inserts jb welded on either end of the 7mm tube. The adjuster is designed that in event of failure, the adjuster will remain within the air tube opposed to being ejected. Its wicked how well the adjusters port blends into the existing valve porting (seen below), one can barely tell its present when fully open. I drilled the 7mm bore through the valve on the opposing end of the OEM adjuster as the magazine sticks out from the right of the gun, I thought it be best to avoid adding a knob right next to where the magazine protrudes from.
The 7mm bored hole leaves less than 1mm between it and the .238" throat I run, as well as roughly 1mm between the valve exit port and the valve seats lowest point AND roughly 1mm and change at the top of the exit port, meaning there is very, very little room for error in placing a 7mm hole into a marauder valve ported to .23" for a tp adjuster. Going just .03" off in one direction means you're breaking through and ruining a valve, or impeding air flow through the throat. I did only use a hand drill, but I ended with a piece of 80 grit sandpaper rolled around a drill bit to really dial in the last hundredth of an inch for placement.
In 25 cal with 34 grain, the power wheel currently will take the power down at max from 65 fpe to 25 fpe at min. In 22 cal with 15.89 grains the power wheel cuts the power from 35 fpe down to around 17 fpe. So in both calibers it cuts the power satisfactorily well. If I ran slightly smaller ports I would be able to shave more power off but frankly I hit my goal and realize the limitations of space constraints in a marauder valve.
The primary reason I went this direction on my marauder is due to running a pilot valve that is hard to tune to both low end and high end in the sense that, it just wants to open/flow, which results in choking the airway being the most effective way to limit power versus solely relying on hammer spring. Choking airways and remaining within 95% of your airguns peak power output is most ideal for consistency, and running large ports limits an airguns power range unless an ability to choke/reduce airways is available or you wildly swing reg pressure around. This makes it easy to setup a rifle to shoot both slugs and pellets, shoot high or low power, or simply just pellets with large weight difference without having to tweak your regulator settings a ton. Freedom!
The knob matches my rear hammer spring / ssg access knob that I use to change my ssg carriers on the fly, also matches my stainless probe. I like how the dial indicator hash marks and numbers come close to matching the stock marauder engravings, I do wish the black was a little less glossy but I don't mind it having a little pop.
-Matt
Not that anyone really mods marauders anymore, but ya never know what kind of history will repeat itself. I have yet to see this mod done on a maraauder so I figured I'd share.
I found the stock velocity metering screw on marauders lack luster, requiring an Allen key to adjust, while being limited on how much it can restrict with large ports, I decided to add a quarter turn transfer path adjuster as many modern pcp's have. (Plus I shamelessly epoxied my VMS bore ages ago as it was the in thing to do at the time). I have another unregulated marauder that I may keep the stock OEM setup, but probably not.
The adjuster I fabricated is made from 7mm stainless steel tube with 4mm ID, opened up where it matters to .235"x.215" for a perfectly blended .225" exit port going through my valve. It's retained by a 4-40 screw and the knob is also 4-40, both of which were pressed inserts jb welded on either end of the 7mm tube. The adjuster is designed that in event of failure, the adjuster will remain within the air tube opposed to being ejected. Its wicked how well the adjusters port blends into the existing valve porting (seen below), one can barely tell its present when fully open. I drilled the 7mm bore through the valve on the opposing end of the OEM adjuster as the magazine sticks out from the right of the gun, I thought it be best to avoid adding a knob right next to where the magazine protrudes from.
The 7mm bored hole leaves less than 1mm between it and the .238" throat I run, as well as roughly 1mm between the valve exit port and the valve seats lowest point AND roughly 1mm and change at the top of the exit port, meaning there is very, very little room for error in placing a 7mm hole into a marauder valve ported to .23" for a tp adjuster. Going just .03" off in one direction means you're breaking through and ruining a valve, or impeding air flow through the throat. I did only use a hand drill, but I ended with a piece of 80 grit sandpaper rolled around a drill bit to really dial in the last hundredth of an inch for placement.
In 25 cal with 34 grain, the power wheel currently will take the power down at max from 65 fpe to 25 fpe at min. In 22 cal with 15.89 grains the power wheel cuts the power from 35 fpe down to around 17 fpe. So in both calibers it cuts the power satisfactorily well. If I ran slightly smaller ports I would be able to shave more power off but frankly I hit my goal and realize the limitations of space constraints in a marauder valve.
The primary reason I went this direction on my marauder is due to running a pilot valve that is hard to tune to both low end and high end in the sense that, it just wants to open/flow, which results in choking the airway being the most effective way to limit power versus solely relying on hammer spring. Choking airways and remaining within 95% of your airguns peak power output is most ideal for consistency, and running large ports limits an airguns power range unless an ability to choke/reduce airways is available or you wildly swing reg pressure around. This makes it easy to setup a rifle to shoot both slugs and pellets, shoot high or low power, or simply just pellets with large weight difference without having to tweak your regulator settings a ton. Freedom!
The knob matches my rear hammer spring / ssg access knob that I use to change my ssg carriers on the fly, also matches my stainless probe. I like how the dial indicator hash marks and numbers come close to matching the stock marauder engravings, I do wish the black was a little less glossy but I don't mind it having a little pop.
-Matt
