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Author Topic: marauder upgrade  (Read 1646 times))

Offline bear air

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Re: marauder upgrade
« Reply #60 on: June 29, 2022, 08:06:01 PM »
My first PCP rifle was a 25cal Armada. It had the GM barrel. I ended up get a barrel from Jim Gaska for it. The GM barrel was very accurate. I sold it without even knowing what I had. It went to a good home though. I think the newer style 25 barrels are very good too though.
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Offline Richard3589

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Re: marauder upgrade
« Reply #61 on: June 29, 2022, 08:22:40 PM »
 I may find out one day. Right now I'm really enjoying my .22 Marauder. I also have a couple springers. One in . 22 and one in .25. I usually shoot the 50 ft casual on here with my Hatsan 95 .22. lately I've just been concentrating on fine tuning the Synrod. Getting close every day without many extra upgrades. I'm still afraid to mess with internals much, so port and hammer adjustments have mainly been it. Still have room in the port but don't want to open wide open. It might start burping air then, but I don't know. Like I said , I'm pretty green on PCPs.
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Offline DHunter

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Re: marauder upgrade
« Reply #62 on: July 22, 2022, 03:29:08 AM »
I got a .25 Marauder in Nov 2020 but it sat collecting dust until last month because it leaked so badly and getting service during COVID was difficult.  Now after a warranty repair it holds its charge super well.

I've wanted to get it launching the 34-grain JSBs at 850fps, 55fpe, but I've been trying the different tuning methods I found online and there doesn't seem to be any combination of adjustments that will get me more than about 800fps (48.5fpe).  I've looked all over this GTA forum, but trying to find information here is kind of like trying to drink from a fire hose.  I was on the more-focused Marauder forum in its dying days, but it's gone now.  Can someone suggest some good resources?
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Offline Hajimoto

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Re: marauder upgrade
« Reply #63 on: July 25, 2022, 08:24:02 PM »
I got a .25 Marauder in Nov 2020 but it sat collecting dust until last month because it leaked so badly and getting service during COVID was difficult.  Now after a warranty repair it holds its charge super well.

I've wanted to get it launching the 34-grain JSBs at 850fps, 55fpe, but I've been trying the different tuning methods I found online and there doesn't seem to be any combination of adjustments that will get me more than about 800fps (48.5fpe).  I've looked all over this GTA forum, but trying to find information here is kind of like trying to drink from a fire hose.  I was on the more-focused Marauder forum in its dying days, but it's gone now.  Can someone suggest some good resources?


The information you are looking for is on here, you just need to master the search feature. Go to advanced and you narrow down the scope of your search.
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Offline DHunter

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Re: marauder upgrade
« Reply #64 on: July 25, 2022, 08:28:36 PM »
Well, Hajimoto, I think highly of you, but I have spent dozens of hours of searching and reading topics about Marauder tuning and it's not getting me there.  I was hoping that someone would remember a particularly helpful thread.  Sometimes someone's memory is a lot better than a search function that lacks human intelligence.
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Offline Hajimoto

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Re: marauder upgrade
« Reply #65 on: July 26, 2022, 04:09:40 AM »
Well, Hajimoto, I think highly of you, but I have spent dozens of hours of searching and reading topics about Marauder tuning and it's not getting me there.  I was hoping that someone would remember a particularly helpful thread.  Sometimes someone's memory is a lot better than a search function that lacks human intelligence.
I understand completely. I built a few Marauders and I can tell you that in order to get a .25 caliber to 55fpe you will need to modify the Marauder to some degree. Modification variables are hammer, hammer spring, barrel transfer port opening, and valve work.


Here are some things to consider which will also help you GOOGLE any one of them for more specifics regarding that topic


  • Start with replacing the hammer spring with a 10# spring.
  • Make sure your valve metering screw is back all the way out as described in your owner's manual.
  • Open up barrel transfer port to 3/16" (0.1875)
  • Replace the transfer tube with a larger ID port for greater airflow.
  • Increase Valve exhaust port ID
  • Increase Valve Throat ID


Here is an oldy but a goodie from Bullfrog. When you watch this video you will learn a lot about what it takes to extract greater power out of your Marauder



I hope this helps
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Offline Motorhead

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Re: marauder upgrade
« Reply #66 on: July 26, 2022, 12:54:35 PM »
In ADVANCED search ... You can also add a Specific Poster / Member and then keyword MARAUDER and get the most bang for your search buck  8)

I had done LOTS of marauder mod posts here 7-10 years ago.  Search member MOTORHEAD to find them.

There were Many of us years back that did extensive work on that platform, sadly the member names escape me now ???
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Offline Frank in Fairfield

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Re: marauder upgrade
« Reply #67 on: July 26, 2022, 02:22:50 PM »
I got a .25 Marauder in Nov 2020 but it sat collecting dust until last month because it leaked so badly and getting service during COVID was difficult.  Now after a warranty repair it holds its charge super well.

I've wanted to get it launching the 34-grain JSBs at 850fps, 55fpe, but I've been trying the different tuning methods I found online and there doesn't seem to be any combination of adjustments that will get me more than about 800fps (48.5fpe).  I've looked all over this GTA forum, but trying to find information here is kind of like trying to drink from a fire hose.  I was on the more-focused Marauder forum in its dying days, but it's gone now.  Can someone suggest some good resources?

You are only going to have 55fpe at the muzzle…maybe.
The energy bleeds off very fast (Check ChairGun).
My .25 shoots @ 40fpe and has dropped every mammal it has shot at with one shot.
Just get a nice tune and then get closer.
I was an archer in my earlier days and still shoot a muzzle-loader (in addition to the 499b) so getting close is normal for me.
Too, I have harvested (politically correct term) four Pronghorn antelope and not one of them was more than 75 yards away.
Enjoy the hunt.
Get close.
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Offline bear air

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Re: marauder upgrade
« Reply #68 on: July 26, 2022, 08:59:40 PM »
My armada shoots the hades around 880 fps which is around 43 fpe or so and I agree with Frank about that being plenty of power. 50 yards no prob. Your still dropping 30 fpe out at 50 yards I imagine. There's programs out there that figure that crazy stuff out.
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Offline DHunter

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Re: marauder upgrade
« Reply #69 on: July 31, 2022, 10:04:03 PM »
Thanks everyone.  I expect to be able to work on it more this week.  I will probably go for a stronger hammer spring if I can find the right thing to order; but I don't think I want to go crazy with the modifications since I'm not too far from the goal.

My armada shoots the hades around 880 fps which is around 43 fpe or so and I agree with Frank about that being plenty of power. 50 yards no prob. Your [You're, contraction of "you are"] still dropping 30 fpe out at 50 yards I imagine. There's programs out there that figure that crazy stuff out.

Hard Air Magazine's test of this pellet says in the article at https://hardairmagazine.com/reviews/jsb-exact-king-heavy-mkii-33-95-grain-25-caliber-pellet-test-review/, "As Chairgun shows, no less than 73% of the Muzzle Energy is retained by JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets even at 60 Yards range."
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Offline Richard3589

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Re: marauder upgrade
« Reply #70 on: July 31, 2022, 11:41:14 PM »
Hey everyone,went out the other day in 103 degree temps and did some Chrono work with my Marauder .22, so these numbers may be a little higher than normal temps. Not sure how that works. Anyways,shot multiple pellets and one Griffin slug near the peak of the shot curve. Seems to be between 2700 and 2000 psi. These were done at the peak around 2600 fps.

 17.6 Norma = 874.6
  18.13 jsb = 854.9
  21.14 H&N = 814.3
  25.43 Jsb jumbo = 733.7
  14.3 Jsb dome = 976.2
   19gr Griffin HBHP = 814.4
 Seemed like good numbers. Just thought I would share.
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