Medium power .22 Marauder setup

[sperho]

Many are chasing the most power that they can from their PCPs, but I purchased the Marauder for it's low cost, reasonable accuracy, quietness, and tunability for either longer distance plinking or shorter distance target shooting.  To that end, I've already posted my "higher power" tune (~25 fpe) results in another thread.  This thread is to share what my medium power tune looks like.  This pellet speed produces nice 1 ragged hole groups with wadcutters at 10m, whereas the 25 fpe tune shotguns flat-faced pellets.  I'm happy with these results and I now have more than one gun that works well for 10m off-hand match-style shooting.  Especially nice is that one is a PCP that I can get about 50 shots with a middle of the road fill pressure and pressure-spread and retain POI quite well at 10 m.  I'm posting the entire string (in the Google docs link below the chart) starting from an excessively high fill pressure so that you can see how having too little hammer preload coupled to a short hammer stroke doesn't balance well with higher fill pressures.  The string that is highlighted in green is the string of greatest interest to me because it produces a speed that is about 4% within max velocity for little POI variation.  The plot is of only these shots.  Average energy is about 15 fpe near the muzzle with CPHP pellets.

A few details on the tune if you are not inclined to open the spreadsheet link below the chart:


Metering screw = 2 turns out from full in
Hammer preload = full out (minimum preload)
Hammer stroke = 10 turns in from full out (near minimum travel)
Optimum fill pressure =~ 2100 psi
Optimum end pressure =~ 1400 psi
# of shots within ~4% of max velocity = 49
Efficiency = 1.15 fpe/CuIn
# fills I could get out of an 80 CF, 3000 psi SCUBA tank using a starting pressure of 2100 and end of 1400 = 65!



The chart:



The data (in a Google doc spreadsheet), including tune info:  https://docs.google.com/spreadsheet/ccc?key=0Auo5v-jZ9NUjdEpzQ3hIaEpET1NFOEs1RHZlVzZwSkE&usp=sharing

[rsterne]

Hey, you turned your MRod into a detuned Disco!.... sorry, couldn't resist.... A Disco has a smaller reservoir, though....

I love it when guys explore the lower power / long shot string side of things.... You can make some awesome guns by restricting the power to only what you need for the job....

Bob

[sperho]

Hey, you turned your MRod into a detuned Disco!....

Exactly!  This gun is wonderful as two guns in one...  Almost as much air as a Disco Double, the great trigger, lower fpe than the Disco if you'd like, great shot string for target work, and 5 minutes later it can be pushing 30 fpe.  Love it...