Finally found my Marauder tune - and tried some JSB's (!)

[TheBaron]

I picked up a used Gen1 Marauder in .22 a few weeks back. After struggling with tuning (even though I had tried the "A-Team" method) I'm finally at settings that give me good velocity with decent air efficiency. My goal is hunting pigeons (primarily) out to 50+ yards. I have a scuba tank and am never far from the truck, so air efficiency is not critical but I'd like to get 20 shots per 2800-2900psi charge. I had started out way too light on my Hammer Spring (HS) pre-load with too long of a Hammer Throw (HT), so my gun was an air pig with constantly decreasing velocity right from shot #1. I'm now at +8 turns CW for HS (only about 3/4 turn from full bind so I think I will buy a heavier HS) and a very short HT setting of + 13.75 turns CW. I have found at this short HT the settings are veeery sensitive, and even 1/8 turn shows results. I've left the air valve at + 3.75 turns CCW from closed and am getting about 820 fps with the 18-ish grain pellets, which my gun seems to like. I still don't have much "flat" time on my velocity curve, so I will tweak and tune a tiny bit more as time permits, but I've got about 15-17 very usable hunting shots now and I am satisfied.

As for accuracy, I'm a PCP newb and this is my first air gun in 30+ years so I was a little worried when I read about the "Crosman .22 barrel lottery" after I had already bought my Marauder. I had tried the H&N Baracuda Hunter 18.41gr. HP pellets already and knew my gun liked them, but I had not tried the JSB Exacts yet. Once I found my tune yesterday, I did some 25yard accuracy testing. I shot a 10-shot group with the H&N first and was very pleased with the results. Then I broke the seal on my first tin of JSB pellets (Exact Jumbo Heavy 18.13gr) and, with much anticipation, settled in for a 10 shot group. As you can see, they certainly lived up to all I've been reading about their accuracy capabilities - wow! I'll look forward to getting back out and seeing how these two hold up at 50 yards, but it looks like I did OK in the lottery.

FYI... Canadian dime/nickel are almost exactly the same dimensions as US... they're just worth 30% less. LOL

 

[NorthLand43]

Good to see someone else got a good Marauder in .22! I have read a lot about accuracy issues with the .22 barrel, but I think I got a good one myself. It is a Gen I. 
Glad to see you dialed it in!

 

[30cal]

 Wow you did get a good barrel! I had to replace mine with a $210. (US) Hammer forged barrel to get that kind of accuracy with JSB 18s'. I have a first gen .22 also and have modified it with a Tim Hill high flow valve, .160" transfer port and his high volume gauge block as well as a Huma .25 cal regulator. I set this gun up for high power regulated operation for long range target shooting and wanted a flat shot string (no curve). I get 17 shots at 960 fps with the JSB 18gr. that's 39 fpe. I'm telling you all this to show that there is still room for improvement in efficiency . (Heck I'm sure there is still room for some improvement in my tune as well) I have a regulator which takes up volume in the air tube and am still getting the same number of shots at much higher power.
Now it may be that that is about all that can be done with the stock valve. AJshoots would be able to tell you more about tuning the stock valve. I would back the restrictor screw all the way out and just use the hammer throw and spring adjustments. The high performance after market valves do not use flow restrictors. You are off to a good start though. Good luck.