I tuned my marauder for high power it has a custom 15 in barrel and the valve modified the throat to .266 and ports through valve and barrel is .220 still using the stock trasnfer port. And using a 16 pound heavy hammer spring. But for some reason i still get valve lock on 3100 psi and it says I'm only pushing 30 grain pellets at 810 fps on the chrony now that was very cloudy this morning so maybe it wasn't reading right hammer adjustment is maxed out for power and vms screw opened all the way up. I'm very confused why it would valve lock with that big of spring.
Benjamin Marauder .25 power tune
- Thread starter anonymous_.457
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Not trying to be difficult but you have opened several threads on Marauder Power Tunes and they always end up about in the same place.
Hitting a relatively stock exhaust valve with heavier and heavier springs and hammers such that you have to have a giant bolt grip to cock the rifle is never going to get you where you want to be and I am not sure you have figured out yet where it is that you want to be.
An unregulated Maraduer valve is set up for a maximum fill pressure of 3000 psi. It is not just the springs but the areas of the components.
Did you go to a lighter valve poppet spring? Why are you filling beyond 3000 psi that is engraved on the side of the rifle?
What does the shot string look like? Does it start at 810, climb to 940 and then back down or does it start at 810 and plummet to oblivion? And over what pressure ranges from start of string to end of string? How many shots?
Whacking the OE valve with heavier and heavier springs and hammers is only going to result in a rifle that is impractical and probably obnoxious to shoot. You ask the same question over and over and have never really defined what you mean by a power tune because I can assure you that my definition of a power tune has nothing to do with a 16 pounds hammer spring. Do you understand that increasing the diameters and area of the HP path past the exhaust valve, that is the valve port, TP and barrel port also increases the volume and will result in a greater pressure drop Delta compared to a rifle with smaller ports, other things like working pressures and otherwise similar setup?
A "power" tune is more than putting in heavy springs and gigantic ports, it might not involve a heavier spring at all. What is a power tune anyways? I think you have mentioned 100 fpe! I am just going to tell you again, you will never get a practical or useful string of shots out of a Marauder .25 at 100 fpe. There is not enough reservoir volume, the valve dimensions available are not sufficient, the rifle breech has no recoil lug to secure it to the air tube and it might sheer off and the breech is not sturdy enough or thick enough in section to resist bending upward at such a pressure and power level.
Hitting a relatively stock exhaust valve with heavier and heavier springs and hammers such that you have to have a giant bolt grip to cock the rifle is never going to get you where you want to be and I am not sure you have figured out yet where it is that you want to be.
An unregulated Maraduer valve is set up for a maximum fill pressure of 3000 psi. It is not just the springs but the areas of the components.
Did you go to a lighter valve poppet spring? Why are you filling beyond 3000 psi that is engraved on the side of the rifle?
What does the shot string look like? Does it start at 810, climb to 940 and then back down or does it start at 810 and plummet to oblivion? And over what pressure ranges from start of string to end of string? How many shots?
Whacking the OE valve with heavier and heavier springs and hammers is only going to result in a rifle that is impractical and probably obnoxious to shoot. You ask the same question over and over and have never really defined what you mean by a power tune because I can assure you that my definition of a power tune has nothing to do with a 16 pounds hammer spring. Do you understand that increasing the diameters and area of the HP path past the exhaust valve, that is the valve port, TP and barrel port also increases the volume and will result in a greater pressure drop Delta compared to a rifle with smaller ports, other things like working pressures and otherwise similar setup?
A "power" tune is more than putting in heavy springs and gigantic ports, it might not involve a heavier spring at all. What is a power tune anyways? I think you have mentioned 100 fpe! I am just going to tell you again, you will never get a practical or useful string of shots out of a Marauder .25 at 100 fpe. There is not enough reservoir volume, the valve dimensions available are not sufficient, the rifle breech has no recoil lug to secure it to the air tube and it might sheer off and the breech is not sturdy enough or thick enough in section to resist bending upward at such a pressure and power level.
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Just to cover some of the usual suspects, the TP is not leaking and the barrel to probe O-ring is in place?
Out of curiosity what were you expecting to see?
Has this arrangement of components and assorted bits done any differently previous? And now it does not?
A .14 stock TP is a pretty big restriction, 810 fps with 34 grain pellets is not far off with that much port restriction.
A custom 15 inches barrel, where did the other 5 inches go off to? A short barrel is not going to help with a "power" tune.
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No leaks at the bolt or TP. Yes it has in my .22 marauder with a .250 throat and 0.203 ports I'm getting about 50 fpe that's on 3800 psi with no valve lock and a 10lb heavy hammer spring. That's why I'm very confused on getting valve lock when my .25 has a heavier hammer spring
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Have you opened the front valve inlet hole at all? Have you hogged out the gauge block?
If those aren't opened up, you won't be getting anymore power out of it. The gauge block is pretty restrictive. Also, for better response and flow, put a bevel on the edge of those ports to direct the air flow to the center of the port.
If you really want more power, you should get the full length barrel or even go for a TJs liner and go longer.
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As for wanting 100 fpe in 25 on this platform... it ain't gunna happen without a powerhouse valve and probably 28" barrel.
My 357 has a huge powerhouse valve, 7.5mm ports, and a stiff ass spring. 16.5" barrel will get up to 150-160 fpe, but it's hard to cock and it kicks like a 22 magnum. Gets like 4 shots on a fill. I have it tuned for 7 shots at 120 fpe with polymags. It's friggin loud.
My 357 has a huge powerhouse valve, 7.5mm ports, and a stiff ass spring. 16.5" barrel will get up to 150-160 fpe, but it's hard to cock and it kicks like a 22 magnum. Gets like 4 shots on a fill. I have it tuned for 7 shots at 120 fpe with polymags. It's friggin loud.
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Yes sir gauge block has been hogged out my valve uses 0.220 port size on the exhaust and barrel port. throat has been drilled to 0.266 and I'm not using the end cap and return spring. And I'm running the 16 pound heavy hammer spring and a polished hammer
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Your transfer port is limiting you.. try a .187 tp. Also radius the valve to port air path.
Also a word of caution on over filling … there is a safety margin… but over time you over stress the tube and valve.. your flirting with disaster going that high repeatedly.
Also a word of caution on over filling … there is a safety margin… but over time you over stress the tube and valve.. your flirting with disaster going that high repeatedly.
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9 shots amidst pitch black....
Look. I´m not here to pee on your parade, the initiative here is to break up a thinking pattern.
Meet... "El-Cheapo".
Worst thing there is, coffee break at the shop. So we went at it, "how far can the cheapest POS around be pushed?"
So coffee break done i bat off and bought the cheapest thing there is around here. One of our hardware stores keep a chinese ripoff on the Beeman Cheif.
In 177 cal.
TBH i was kind of amazed at the build Q of this thing. Really. Sharp tools had been used and then the effin full 9 yards.
Threw the book at it. For real. Which made it end up with an approx 330cc+ tank and what not (see pics).
Now.
177 cal. As chance has it H&N had just launched their "heavy" 20 grain hollow point slugs. Neat enough, so loaded them up right and put the LabRadar of mine next to El-Cheapo.
Startled by one massive bang, suppressor or no... and we looked each other down like the idiots we are.
Walked up to the LabRadar that told... 1288fps. We went supersonic first hit for a cool 100J/73 fpe.
Out of a 177".
Then dialed the thing back so we were subsonic again, picture of target tells the rest. @ approx 30m amidst dark using the rather coarse crosshairs of a Yukon Photon.
What i´m saying is...
Back off.
Question yourself and your obvious lack of results. WHY are they? What do you do wrong?
Be analythical to the approach.
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He is getting about 44 fpe 
. Not bad at all except he only gets one shot .
Not sure that porting for a .25 beyond .16 is needed or benifical for a no-regulator rifle. With a regulator .19 is probably optimal for guns running in the 50 fpe range.
. Not bad at all except he only gets one shot .Not sure that porting for a .25 beyond .16 is needed or benifical for a no-regulator rifle. With a regulator .19 is probably optimal for guns running in the 50 fpe range.
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Currently I'm pushing 30 grain pellets at 810-820 fps with a 15 inch barrel with my valve and ports opened and gauge port hogged out and a 16 lb heavy hammer spring that's how much fps a stock marauder pushes 25 grain pellets....
9 shots amidst pitch black....
Look. I´m not here to pee on your parade, the initiative here is to break up a thinking pattern.
Meet... "El-Cheapo".
Worst thing there is, coffee break at the shop. So we went at it, "how far can the cheapest POS around be pushed?"
So coffee break done i bat off and bought the cheapest thing there is around here. One of our hardware stores keep a chinese ripoff on the Beeman Cheif.
In 177 cal.
TBH i was kind of amazed at the build Q of this thing. Really. Sharp tools had been used and then the effin full 9 yards.
Threw the book at it. For real. Which made it end up with an approx 330cc+ tank and what not (see pics).
Now.
177 cal. As chance has it H&N had just launched their "heavy" 20 grain hollow point slugs. Neat enough, so loaded them up right and put the LabRadar of mine next to El-Cheapo.
Startled by one massive bang, suppressor or no... and we looked each other down like the idiots we are.
Walked up to the LabRadar that told... 1288fps. We went supersonic first hit for a cool 100J/73 fpe.
Out of a 177".
Then dialed the thing back so we were subsonic again, picture of target tells the rest. @ approx 30m amidst dark using the rather coarse crosshairs of a Yukon Photon.
What i´m saying is...
Back off.
Question yourself and your obvious lack of results. WHY are they? What do you do wrong?
Be analythical to the approach.
Upvote 0
Which should be a clue that many if not all of those things were counter productive or of no consequence to your goal of a power tune.
A stock M-Rod has a 20 inches barrel. You are down to 75% of stock right there as the M-Rod barrel is on the short side anyways.
What do you think is limiting you to stock output despite your heavy spring, hogged out ports and short barrel?
A stock M-Rod .25 will make 16+ shots on a Bell curve at 40 to 44 fpe.
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Im gonna chrony it again tomorrow I maxed out the hammer and spring preload I'm gonna see what that does and go from there. And probably get a bigger trasnfer port soon.
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