Another Regulated P-rod

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ajshoots

ajshoots

Member
Apr 1, 2015
2,054
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Uniopolis, Ohio, United States
Just finished up a regulated P-rod for a customer. After the wonderful results with my own regulated P-rod, I was excited to do another!! The Huma P-rod regulator from Nick at Air Superiority is one of the best add ons you could purchase for your P-rod. This gun arrived not shooting and the owner was unsure what was wrong. It ended up being a broken valve poppet. I tore the gun down to replace the poppet and give all the parts my usual Marauder treatment. I reassembled the gun and installed the regulator with the plenum spacer. I did not use the gauge block so that there was as much volume as possible in the little P-rod tube. The gun is now completed, scope remounted and sighted in, just waiting on a shroud ext so I can box it back up and ship back to the owner.

With H&N ftt's, The gun is getting 24 shots @710fps with an ES of 12 and an SD of 3.


 
Hello from Puerto Rico. My first post in this forum.

ajshoots,

I recently got a HUMA regulator for my rapid-70 mini-bullpup Prod. I have been trying to get 16 shots @ 22 fpe but that seems to be not realistic given the 65 cc air reservoir of the Prod. Now I am focused at duplicating a very nice shot string posted here: http://huma-air.com/wp-content/uploads/2015/06/shotstring-Prod-124-bar.pdf

That second shot string of 31 shots @ 18.8 fpe (ES=11; sd=2.8; 582 total fpe!) is the one I am after. Unfortunately, the mods needed to achieve it are not specified in the HUMA website. After opening the tp and valve exhaust to 0.125" and good number of pellets and different springs and HST/HT combinations, I am now stuck at 17 shots @ 18.8 fpe, ES=11. Too far yet in terms of shot count. Nick suggested to try a lighter hammer, so that will be my next step. In the mean time I am trying to get some input and opinions. Any comment or suggestion would be really appreciated.

Cheers,

Miguel
 
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Have you opened the valve throat or increased volume in the valve? I think the lighter hammer is the way to go. I have yet to try and make a lightweight hammer, but might try and turn one out in the near future. I like the prod around 15fpe, so I have not done much to try and make more power. Your results seem to match mine when I cranked the gun up a bit. I got 16 shots at 17fpe with 14.3's. ES 8 sd 2. I am assuming your reg is factory set? I believe that the string on the huma site has the reg pressure slightly increased also?
 
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"ajshoots"Have you opened the valve throat or increased volume in the valve? I think the lighter hammer is the way to go. I have yet to try and make a lightweight hammer, but might try and turn one out in the near future. I like the prod around 15fpe, so I have not done much to try and make more power. Your results seem to match mine when I cranked the gun up a bit. I got 16 shots at 17fpe with 14.3's. ES 8 sd 2. I am assuming your reg is factory set? I believe that the string on the huma site has the reg pressure slightly increased also?
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Thanks ajshoots. I have not mod the valve other than opening the exhaust port. I might try that down the line. I use my Prod mainly to hunt iguanas, which in my experience require 22+ fpe at 30-40 yds., my usual distance. You can do it with 18 fpe at shorter distances. The string on the HUMA site was with a set point of 124, according to the string table. I tried 130 and 140 bar set points, but could not get my 16 @ 22 fpe goal, so turn it back to 124 bar to see if/how the 31 shots at 18.8 fpe tune is doable. We'll see. For now I'll use what I have before going on with the light hammer/valve mods. I'll be following your, and others, progress with the nice HUMA regulator.

P.S. I also tried this tune, but could not duplicate it either:

https://www.google.com/url?q=http://www.network54.com/Forum/79537/thread/1448492911/last-1448538857/Expand%2BThread&sa=U&ved=0ahUKEwiJvKCe87rJAhVJVh4KHdlYB38QFggEMAA&client=internal-uds-cse&usg=AFQjCNFS2fxkzapuhvEgruALhqTDWbpF3w
 
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In the post from the YF the pellets used are JSB's 18.1. He got an average of 736 fps for 16 shots. I did the same mods and got an average of 696 fps. I have no idea why...except that my Prod has a Jim Gaska barrel, which is supposed to be very tight and it has been mentioned that it could reduce the velocity by some amount I don't know. I removed the gauge block when installed the regulator.
 
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The Gaska barrel will slow the gun down some. The above gun I worked on would not produce the same velocity as mine, and the only difference was his bore is much tighter than mine.

Just my opinion, but without major internal work, the prod is not capable of much more power than 18fpe. If you need 20+, I would be looking for a different gun. Your results of 695 is really good for 18gr pellets. You can't expect much more!!
 
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Thanks ajshoots for your kind words,

I am afraid your are correct, but as a last resource, and since I really enjoy tinkering and have not too much to loose, I would like to try your suggestion of "major internal work". Could you describe me what exactly that means? In any case I will be happy if I can achieve, or get reasonably close given my barrel restriction, those elusive 582 fpe from 31 shots @ 18.8 fpe, which we know are a real possibility. I have a AAS510 carbine that is very good for my intended purposes, both in terms of power and shot count out of the box, but the size and handling characteristics of the Prod mini-bullpup is another thing.
 
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I am new to regulating these guns, but I am rather certain that a regulator is not going to allow the gun to reach its potential max velocity. Without the regulator, I had the above gun shooting in the 840fps range with 15gr pellets. I didn't run a full string, but it will make alot more power unregulated, but the shot count will be about 8 shots or less. Being new to regulated prods, I have no clue what the potential max is?? All I can suggest is to increase the volume in the valve, by opening up the inner body, the valve cap, and maybe opening the throat up will also help to increase regulated power? If you want max power without the regulator, you want a large open flowing valve with as big of ports as the gun will handle, but again that means very few shots and probably a wide velocity spread on those few shots. Either way, most of the valve work really needs to be done on a lathe. You could get away with a drill press maybe, but you risk ruining the valve. 

And also, I would be very curious as to the full details of how that gun got 31 shots at 18.8fpe!! If I were you, I would contact a fellow named Scott. He goes by the name Motorhead on some forums. I am unsure if he is a member here?? He knows regulated prods and marauders better than anyone else!!
 
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Motorhead hangs out over at Marauderairrifles.com. He makes and sells a light weight hammer for low to moderate power tunes for Mrods. Not sure about Prods. To get high power from a regulated gun you need more plenum volume. In my case I used a Tim hill valve and gauge block which has more volume than stock and a Huma .25 cal regulator which again has more internal air volume than the one for the .177 and .22 version. Its putting out 39 FPE for 16 shots on the reg. I don't know if there is an easy way to get more volume in a regulated Prod as I don't have one. But with the small air tube you would only get a handful of shots per charge.
 
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I have the Hill valve and also the Huma regulator. Guess I should of got the Hill kit for regulated instead of the 25# kit. The Huma comes with a plenum that takes over the guage block as not to loose volume. The Hill 25# kit also comes with some o-rings for the buffer mod. With a regulator, will the buffer mod do anything?

I think I'm gonna have to abandon wanting to make the p-rod a 20fpe for head shots on bandits...and just make it a rat gun only. If so then I'll lower the power to sub 10fpe...but of course that is dependent on the pellets and what they like. I prefer to stick with crossman premiers for lower cost and easy access at wallyworld.
 
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