Anyone achieving Huma's advertised velocity & shot count for their P-Rod reg?

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SteveV

SteveV

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Feb 25, 2018
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As in 30 shots at 18 fpe?

Not having much luck on my end, have left the gauge block & gauge in the tube as I want to know what the reg's putting out. Can't get much more than 13 fpe with any reg output setting, have tried up to 1800 so far, same results as 100 bar/1450 psi setting it came with..

Can't remember where I read about this reg, might have been on this forum??

And btw, HAPPY NEW YEAR!!!!
 
Guilty as charged, Steve. I mentioned Huma's P-Rod claims in one of my posts...

Hopefully with a disclaimer!

FWIW, I've managed to resist ordering a reg for my P-Rod based on suspicions that Huma's claims were 'optimistic'. Sorry if you invested due to my post.

Guess I'll content myself with how well my P-Rod does with (just) HS adjustments and drilling-out the TP.-

18.1 grain FX, TP drilled to .091”, 16 shot power-band- Low= 674, Hi= 704, ES= 30, SD= 10, Average= 691 FPS/19.2 FP.

Mine does average 1" five-shot groups at 50 yards regular as clockwork.
 
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The following diagrams are from Huma's installation manual for the P-rod showing assembly options A and B:
Huma options A and B.gif


Do you know which configuration was tested by Huma to produce the shot string linked above?
Is that what is meant by the "config 1" and "config 2" labels on the shot string graph?

Both options include a plenum spacer so that shouldn't be a limiting factor in terms of power, although the presence of the gauge block in Option A sacrifices precious reservoir volume of an already small tube so that will affect shot count a bit.

My guess is the missing piece of the puzzle is the porting details. Power in the mid-teens (~15fpe) is about what a P-rod produces in factory trim where it has the benefit of 1.5x - 2x as much pressure and a huge plenum. Making it produce 18fpe with less pressure and a smaller volume of air requires big porting.
 
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nervoustrig said:
The following diagrams are from Huma's installation manual for the P-rod showing assembly options A and B:
View attachment 319269

Do you know which configuration was tested by Huma to produce the shot string linked above?
Is that what is meant by the "config 1" and "config 2" labels on the shot string graph?

Both options include a plenum spacer so that shouldn't be a limiting factor in terms of power, although the presence of the gauge block in Option A sacrifices precious reservoir volume of an already small tube so that will affect shot count a bit.

My guess is the missing piece of the puzzle is the porting details. Power in the mid-teens (~15fpe) is about what a P-rod produces in factory trim where it has the benefit of 1.5x - 2x as much pressure and a huge plenum. Making it produce 18fpe with less pressure and a smaller volume of air requires big porting.
Click to expand...
How much difference could the removal of the forward o-ring on the gauge block make? I missed that detail, but am willing to do another tear down to find out, have spare o-rings on hand lol -
 
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Huma's 30 shots of 18fpe..... Sure it is possible, but not for the average joe who is just going to drop in a regulator. It has been a while since I recorded shot strings of any of my guns. As of late I've just used my chronograph as a means of making sure guns are still shooting where they were tuned to.

This thread prompted me put my little Prod carbine across the chronograph for a full string. This barrel is rather loose and prefers FTT's with 5.54-5.55 head diameters. Note I used 2 Prod mags and 2 modified Mrod mags for this string.

iaW1pO3.jpg


There are a lot of little tricks (copied from Motorhead/Scott) in this one---2mm stem peek poppet, Cobra chamber, 11gram peek hammer, etc. I tend to port all of my regulated guns to 80% of bore. I used the larger Huma plenum with no gauge. IIRC reg is set around 100-110 bar.

As is typical of the way I tune my regulated/cobra chamber equipped guns, once it falls off the reg, it falls like a rock.
 
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mackeral5 said:
Huma's 30 shots of 18fpe..... Sure it is possible, but not for the average joe who is just going to drop in a regulator. It has been a while since I recorded shot strings of any of my guns. As of late I've just used my chronograph as a means of making sure guns are still shooting where they were tuned to.

This thread prompted me put my little Prod carbine across the chronograph for a full string. This barrel is rather loose and prefers FTT's with 5.54-5.55 head diameters. Note I used 2 Prod mags and 2 modified Mrod mags for this string.

iaW1pO3.jpg


There are a lot of little tricks (copied from Motorhead/Scott) in this one---2mm stem peek poppet, Cobra chamber, 11gram peek hammer, etc. I tend to port all of my regulated guns to 80% of bore. I used the larger Huma plenum with no gauge. IIRC reg is set around 100-110 bar.

As is typical of the way I tune my regulated/cobra chamber equipped guns, once it falls off the reg, it falls like a rock.
Click to expand...
So I'm a regular Joe. WTF is a cobra chamber?
 
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SteveV said:
So I'm a regular Joe. WTF is a cobra chamber?
Click to expand...
"Cobra Chamber" is the name given to something Scott S and Travis W developed some years ago. It replaces a stiff valve spring with an "air spring" of sorts. This allows for faster opening/closing of the valve but without a heavy valve return spring. Opening/closing rate can be tuned by swapping jets. Scott S/Motorhead has written extensively about this tuning tool over on GTA.

Light hammers and easy opening valves can give be a bit erratic, adding a properly designed/tuned cobra chamber can damp things much like a heavy valve spring does.

Similar results can be obtained using traditional methods., but heavy hammers/springs create a shot cycle that I am not fond of. I prefer the shot cycle that is created when combining ultralight hammers and easy opening valves. The shot cycle is very snappy, with little to no noise/vibration from the hammer strike.

Giving credit where credit is due, Scott S pioneered this tuning style upwards of a decade ago.
 
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SteveV said:
Yep, it ends up I've been running it wrong by not removing one of the gauge block o rings, SO the plan is to remove the gauge assembly, a stiffer hammer spring, and see what happens.

The gauge presently shows 2000 psi from a 3000 fill, so the reg's output is just slightly over 135 bar, per Huma
Click to expand...
IMO, once you decide to go regulated, there is no reason NOT to open up the ports. Up to 75-80% of bore size is a good target and easily obtained with common tools. This will allow for comparable energy levels at lower pressures, requiring less hammer strike, less valve dwell, etc.

Good luck!
 
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