I have mine shooting 700 fps, and just like Woodsie said it does best from 2800 to 1500 psi, it's also more accurate at 700 fps, give it a re-crown and it will be even better.
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P-rod got stronger as air pressure decreased, go figure.
- Thread starter bltefft
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All well and good, if one wants to fiddle with hammer spring preload while shooting. Some might well not want to do that. I'll stand by my statement as describing two generally utilized methods of "tuning" an unregulated gun.
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With the original tune, my velocity increased for about 25 shots then plateaued for about 10 and then started down. Peak was 640 fps. That was with a 3000 fill. So I dropped my fill pressure to 2500 psi. That eliminated 15 lower velocity shots from the string. Velocity still increased to about 2000 psi but only by 40 fps. If you want less velocity spread you could fill to lower pressure. You could get it to just go down by filling to about 2000 but I recommend filling a little higher and go at least 20 fps up then 20 fps down. Or 40 up and 40 down.
I wanted more velocity so I turned the hammer spring in. I thought I went 7 turns - effectively the maximum - but I only went about 4 - not much more than stock. I still didn't like the velocity (I wanted 700) so I drilled the transfer port to .1015 (stock is .080). With 7 turns in on the hammer spring I got 780 fps but velocity drops fairly quickly from a 3000 fill. I wanted more than 1 magazine so I tried lower hammer spring settings. I settled on 5 because it gave me the least velocity variation and about 20 shots over 700 fps with a 2700 fill pressure.
I will probably try going back to a stock transfer port with 7 turns in on the hammer spring and if that is still a little low, I will try a .096 transfer port. I think the .1015 is a little big for what I want. It's nice that the parameters are pretty easy to change. It's accurate at the current tune and shoots through squirrels nicely so I am not anxious to retune it but when I get bored I probably will.
I wanted more velocity so I turned the hammer spring in. I thought I went 7 turns - effectively the maximum - but I only went about 4 - not much more than stock. I still didn't like the velocity (I wanted 700) so I drilled the transfer port to .1015 (stock is .080). With 7 turns in on the hammer spring I got 780 fps but velocity drops fairly quickly from a 3000 fill. I wanted more than 1 magazine so I tried lower hammer spring settings. I settled on 5 because it gave me the least velocity variation and about 20 shots over 700 fps with a 2700 fill pressure.
I will probably try going back to a stock transfer port with 7 turns in on the hammer spring and if that is still a little low, I will try a .096 transfer port. I think the .1015 is a little big for what I want. It's nice that the parameters are pretty easy to change. It's accurate at the current tune and shoots through squirrels nicely so I am not anxious to retune it but when I get bored I probably will.
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I emailed a professional Benjamin Marauder mechanic (he has owned his own shop in Ga for many years - and specializes in m-rods and p-rods) about what I experienced with my p-rod and asked him about adding a regulator to a prod. He already has one of my other p-rod to fix a leak, and since he has it, thought it would be wise to move on a reg while he still had the p-rod
Here's his reply:
"Hi,
I have your gun sealed up and am just letting it sit for a few days to make sure it's ok...
As for installing a reg.. It can be done but the tube is so short you won't get many fills.
As for tuning your Prod. You want to mess with the hammer throw not the hammer spring. The hammer throw helps with consistent shot count/fps the best. If you want a reg. in your Prod it would run $175. Not worth it in my book.
Thanks Roy"
So, no reg for me. I'm going to increase the hammer throw to get a little more air out of the tank per trigger pull. I'm also going to stop maxing it out when I fill it - maybe, take it to 2800 psi.
Here's his reply:
"Hi,
I have your gun sealed up and am just letting it sit for a few days to make sure it's ok...
As for installing a reg.. It can be done but the tube is so short you won't get many fills.
As for tuning your Prod. You want to mess with the hammer throw not the hammer spring. The hammer throw helps with consistent shot count/fps the best. If you want a reg. in your Prod it would run $175. Not worth it in my book.
Thanks Roy"
So, no reg for me. I'm going to increase the hammer throw to get a little more air out of the tank per trigger pull. I'm also going to stop maxing it out when I fill it - maybe, take it to 2800 psi.
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I have a reg in mine now. Before that a year with a SS valve. I get 25 shots at 717fps with 14.3’s. Shot string is flat as a pancake. Totally worth it but absolutely not necessary. Just depends on what you demand out of a gun.
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Then just do the tune I suggested on the previous page. It will only take you a couple minutes and you’ll be happy. It’s basically a 600fps tune and my gun shot very well at those settings. And you don’t have to fill to 3k.
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One of the most important things to consider is what you want the gun to do. Plinking or punching paper you might want lots of lower velocity shots. Hunting you might want the max power with less need of several mags per a hunt. I myself don’t believe in low power trying to save the gun. They are cheep and easy enough to repair and modify. Who buys a fast car to putt around in.....
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Not sure I follow you when you said "Turn your hammer throw full CCW, then put 1 turn CW. " Do you mean to turn it CCW until it stops turning, then go back a full turn CW?
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I should probably try the hammer through setting more but the changes I have done in it's setting did not change velocity at all and didn't seem to affect accuracy. I don't understand why a tuner would recommend changing it. Makes me think I might have missed something.
Easy way to decide on fill pressure is to shoot an entire shot string through a chronograph (if you do not have one, there is a chinese model available for $30 or $35 from Amazon). I did not write down the pressure after each shot but wrote it down about every 10 shots. Every 5 would probably be better. Then you just note your peak velocity, the pressure that produced it, and decide how far down you want to go on both sides. For plinking, something like 40 or 50 works well for me. Even short range hunting that isn't too much velocity variation - it won't affect POI noticably. If you want to shoot longer range or more seriously, 20 fps is probably better. It's a lot better than just guessing.
Easy way to decide on fill pressure is to shoot an entire shot string through a chronograph (if you do not have one, there is a chinese model available for $30 or $35 from Amazon). I did not write down the pressure after each shot but wrote it down about every 10 shots. Every 5 would probably be better. Then you just note your peak velocity, the pressure that produced it, and decide how far down you want to go on both sides. For plinking, something like 40 or 50 works well for me. Even short range hunting that isn't too much velocity variation - it won't affect POI noticably. If you want to shoot longer range or more seriously, 20 fps is probably better. It's a lot better than just guessing.
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Here's a question for the smart people: If your P Rod is regulated (huma, etc), what effect does adjusting the hammer spring and hammer throw?
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I'd say that it would need less hammer energy if regulated but that hammer settings could possibly be lowered enough to notice a change if below the "set point" of the regulator. Not sure that one would gain anything by doing so as the function of the regulator would be to provide a stable shot string.
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Yes, it will be bottomed out against the front of the hammer when you go CCW till it stops. Then turn it 1 turn and the little thing will stick out a little. The key is getting it to stay there. Weed eater cord or some loc-tite
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When I regulated mine I eliminated the throw button because I made my hammer and spring all one piece to eliminate hammer bounce. Your hammer spring is always important, regulated or not, $200 gun or $2,000 gun.
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If you get the shorter but stronger hill hammer spring then the hammer is slightly loose when uncocked which will prevent hammer bounce also. Or cut couple of coils off of stock spring, both work but I would suggest OP just cut his since it’s just for target shooting....if he wants to get rid of the hammer bounce which isn’t a big deal.
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Vetmx and qball nailed it as well as many others here being spot on, and, by all means don't forget the other "Marauder tuners" here on AGN that can help you make your Prod Sing... Mine does, thanks to all of them 
.
Have fun,
Patrick
.Have fun,
Patrick
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My PROD only has 20 (can do 22, actually) very accurate shots from 2500/2550 to 2000/2050 PSI, but it does have a 1701P tube, which is very short.
Hammer is a .038" Magnum Air Power--no preload.
Hammer striker is set to 3 full turns from maxed in, so it protrudes and has less striking power.
In short, it is built for low power.
I don't have a chrono, but I am basing the tune on a target at 25 yards, and it is almost pellet on pellet.
It favors 15.89g JSB's over its 13.43 sibling.
Hmm, I have heard good things about the 14.35 JSB's as well as the 5.53 H & N FTT's.
I ordered some of the latter, as they are still available.
Hammer is a .038" Magnum Air Power--no preload.
Hammer striker is set to 3 full turns from maxed in, so it protrudes and has less striking power.
In short, it is built for low power.
I don't have a chrono, but I am basing the tune on a target at 25 yards, and it is almost pellet on pellet.
It favors 15.89g JSB's over its 13.43 sibling.
Hmm, I have heard good things about the 14.35 JSB's as well as the 5.53 H & N FTT's.
I ordered some of the latter, as they are still available.
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I am building a silver hybrid one that looks like an AR of some sort
Waiting for the matching grips:
Waiting for the matching grips:
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