I’m new to this just playing around trying to learn to tune my marauder. I attained my goal of achieving 900 fps with a 10.5 grain pellet. I was refilling to 2500 psi shooting down to about 2200 psi. Everything was perfect. When I refilled to 3000 psi my velocity dropped to 744 and worked its way back up to about 880 after 30 shots. What’s going on?
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Tuning Ascending shot string
- Thread starter UncleB
- Start date
You need a little more hammer spring I believe. With the airtube full the poppet sealing your valve is being held closed with 3,000 psi, as you shoot it down the pressure drops and the valve is easier to open because it is being held closed by less pressure.
When you get a good tune your velocity will have a small rise to a peak then a small fall to refill. It’s an unregulated gun regulating itself. Coolest thing about pcps with knock open valves in my opinion.
Beau
When you get a good tune your velocity will have a small rise to a peak then a small fall to refill. It’s an unregulated gun regulating itself. Coolest thing about pcps with knock open valves in my opinion.
Beau
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SqrlHntr
Member
What you are seeing is normal for an unregulated marauder, but should not be that low at 3k, IMO. Hammer pretension might be a touch light. Basically at higher pressures, the valve needs more energy to open, likewise it closes faster too leading to a shorter amount of time the valve is open and thus slower speeds. As you approach lower pressures with more shots, the energy required to open the valve is less, and the valve opens longer. This is where the fun of marauder tuning is, flattening the curve or straightening the knee as much as possible. Sounds like you are almost there though. Keep tuning!
Also check out hard air magazines technical series on pcp’s. Great read for understanding pcp’s. First article below.
https://hardairmagazine.com/buyers-guides/airgun-buyers-guides/ham-airgun-technical-how-pcp-airguns-work/
Also check out hard air magazines technical series on pcp’s. Great read for understanding pcp’s. First article below.
https://hardairmagazine.com/buyers-guides/airgun-buyers-guides/ham-airgun-technical-how-pcp-airguns-work/
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I’m not a marauder guy, very little experience with them. Did you adjust the throw? It would be the smaller bolt right in the center of the hammer. Backing out the screw increases throw which increases velocity, doing the opposite does the opposite. It gives your hammer more travel. You also may just have to start you string at a lower pressure. You may not have enough hammer spring in the gun to achieve exactly what you want. That’s all I’ve got on the mrod.
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Also I wouldn’t change springs or ports just yet if you were thinking about it. I’ve read from the most reputable tuners on forums of numbers you can achieve with a factory marauder tuned properly, and it’s pretty impressive.
thats really all I’ve got on the mrod!
thats really all I’ve got on the mrod!
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SqrlHntr
Member
welcome! Imo, 880 max from 900 max isnt that far off for a Hammer spring to be off, even 1/4 turn can do some changes in speed. Try a dry lube coating in the hammer area and hammer, fine graphite works well. Hammer could be slowing, happens in m-rods. If thats not it and your settings are not far off ( the hammer spring pre tension may come out of adj some during shooting, check the striker too)check for a leak at the breech o-ring and transfer port seal, tissue paper over the breech while shooting seems to be the trick. Thats where i’d start. Hope it helps.
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It's fairly involved but I did a Bstaley tune (O rings around the valve stem) to flatten the shot curve of my Prod. I think I used 4 and they were sized to be just larger than the inside of the air tube. I put a light coat of silicone grease on them so they stay in place better. They stick out slightly so your hammer can depress them and hit the valve but when the hammer bounces back towards the valve it should not get there. I had to go to a stiffer hammer spring to get back to where I wanted to be with velocity. I got about twice as many higher power shots with about a 30 fps ES. That is not as good as I normally get from my regulated guns but seems pretty decent for an unregulated.
The other alternative is just to fill to a lower pressure and quit when your velocity is lower than you want. Nothing wrong with this, just not as many shots before a refill.
The other alternative is just to fill to a lower pressure and quit when your velocity is lower than you want. Nothing wrong with this, just not as many shots before a refill.
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Normal for none regulated shot string.
one way to deal with it is only fill go certain level.
shoot the number of shots in good range.
one way to deal with it is only fill go certain level.
shoot the number of shots in good range.
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Thanks for all the responses, I will probably be buying some aftermarket parts and modifying it for the better in the future but in the meantime I plan on trying learn to get the most out of it in its factory form.
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