Tuning Gen 2 MRod .177 / Hill Valve / Huma Reg @133'ish

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jdanvers

jdanvers

Member
Jul 7, 2019
951
372
South Central Upstate NY, United States
. . . the gun is shooting nsa 12.5g slugs really well. Really well. I'm inclined to just leave it alone BUT (lol) . . .

Curiously - dialing the HS on this thing doesn't appear to change the speed *at all* - it's a pretty consistent 960-965fps with the HS backed all the way out or even 3 or 4 full turns in. The speed just doesn't change. This tells me that something ain't quite right. I'm inclined to pull the huma up out of the tube ( I've got a wire tied to it - anyone who's tuned m-rods knows what I'm talking about ) and turn it down - thinking maybe I've got it to hot at the 133'ish setting? I couldn't get the velocity for the slugs with the crosman OEM valve - it topped out in the low 940's and I'd already discovered that this gun with those slugs really likes 955-965 - I ran it unreg'd for a brief time testing / experimenting. So . . . I bought the Hill valve and YOWZA - the thing is like it's on steroids now!!

Again - it's shooting really well. It's not terribly efficient though - I get 30 good shots out of it and then it starts to fall off. Point of impact starts to gradually drop starting around shot 34 - 35 and that is very repeatable. I guess my only reason ("need"?) to pull it apart and dink with the reg is just to see if I might be able to get slightly better fuel efficiency out of it ( maybe 40-45 shots - or more? ) vs. the 30 I'm getting now.

More specs - I've got a nylon ( I forgot what you call them ) hammer in it that "Rocker" from GTA made for me and @present I'm using the slightly heavier OEM hammer spring. I do have one of Tim Hills lighter springs.

I'm open to suggestions.

* OR *

I might just leave it alone. ( it's only a 3000 psi fill anyway so its kinda like - who cares? lol ) BUT . . . . somethings not quite right with no change of speed when dialing hs up/down I'm thinking . . .

Thanks guys
 
. . . the gun is shooting nsa 12.5g slugs really well. Really well. I'm inclined to just leave it alone BUT (lol) . . .

Curiously - dialing the HS on this thing doesn't appear to change the speed *at all* - it's a pretty consistent 960-965fps with the HS backed all the way out or even 3 or 4 full turns in. The speed just doesn't change. This tells me that something ain't quite right. I'm inclined to pull the huma up out of the tube ( I've got a wire tied to it - anyone who's tuned m-rods knows what I'm talking about ) and turn it down - thinking maybe I've got it to hot at the 133'ish setting? I couldn't get the velocity for the slugs with the crosman OEM valve - it topped out in the low 940's and I'd already discovered that this gun with those slugs really likes 955-965 - I ran it unreg'd for a brief time testing / experimenting. So . . . I bought the Hill valve and YOWZA - the thing is like it's on steroids now!!

Again - it's shooting really well. It's not terribly efficient though - I get 30 good shots out of it and then it starts to fall off. Point of impact starts to gradually drop starting around shot 34 - 35 and that is very repeatable. I guess my only reason ("need"?) to pull it apart and dink with the reg is just to see if I might be able to get slightly better fuel efficiency out of it ( maybe 40-45 shots - or more? ) vs. the 30 I'm getting now.

More specs - I've got a nylon ( I forgot what you call them ) hammer in it that "Rocker" from GTA made for me and @present I'm using the slightly heavier OEM hammer spring. I do have one of Tim Hills lighter springs.

I'm open to suggestions.

* OR *

I might just leave it alone. ( it's only a 3000 psi fill anyway so its kinda like - who cares? lol ) BUT . . . . somethings not quite right with no change of speed when dialing hs up/down I'm thinking . . .

Thanks guys
Click to expand...

You need to go the other way. Right now you have too much hammer spring for the reg pressure. If you lower the reg it will only get worse. Seeing that you are only getting 30 shots reinforces that you are over driving the valve.
 
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If you really want to increase the efficiency, install a DIY SSG to remove the HS preload (search is your friend). The preload is wasting air per shot as the valve reopens a second or third time after each shot. Also, tune it to 3% to 5% below its max velocity at the given reg set point. You'll then be able to shoot below the set point for a number of shots up to your current desired extreme spread (ES).
 
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Jdanvers,

I wouldn't think that anything is all that wrong. A well tuned Marauder for 12 ft.lbs, gets around 100 shots. To say that you are getting around 35 shots at that velocity......well, in my eyes that's pretty efficient. 

You describe adjusting the hammer spring up and down, and velocity does not change. That tells me that the balance of everything installed is VERY efficient, and the regulator is putting out its max. If you are looking for higher velocity, you are not going to get it unless you open up the transfer port bushing.. Even at that,, you can only push so much air through a given space.. If you up the reg, but get no more velocity, the transfer port is your culprit. If you are looking to get better air mileage, so to speak, the anti hammer bounce devive as mentioned above, would be a good idea.

Judging by the performance that you do have, and what you info you have given above, I'd leave it alone.

Tom Holland 

Field Target Tech 

Fieldtargettech.com 
 
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Jdanvers,

I wouldn't think that anything is all that wrong. A well tuned Marauder for 12 ft.lbs, gets around 100 shots. To say that you are getting around 35 shots at that velocity......well, in my eyes that's pretty efficient. 

You describe adjusting the hammer spring up and down, and velocity does not change. That tells me that the balance of everything installed is VERY efficient, and the regulator is putting out its max. If you are looking for higher velocity, you are not going to get it unless you open up the transfer port bushing.. Even at that,, you can only push so much air through a given space.. If you up the reg, but get no more velocity, the transfer port is your culprit. If you are looking to get better air mileage, so to speak, the anti hammer bounce devive as mentioned above, would be a good idea.

Judging by the performance that you do have, and what you info you have given above, I'd leave it alone.

Tom Holland 

Field Target Tech 

Fieldtargettech.com
Click to expand...

My regged .177 MRod was getting 115 shots at 18fpe, for an efficiency in the 1.5 fpe/cuin range. He is getting approx .79 fpe/cuin. based on the #'s he provided. I hardly think that is "VERY efficient" as you say. Actually just the opposite IMHO.

If you take an adjustable part and adjust it from MAX to MIN with ZERO change, how could you think something isn't right?

I'd bet the gun gets much quieter when he puts the lighter spring in too.
 
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Hi guys . . .

I did put the lighter spring in it (the Tim Hill one) and upon doing so first impression when comparing it to the OEM one is not so much "lighter" to compress in hand ( squishing it together using pointer finger and thumb ) - that "measure" seemed to me anyway - hard to tell. It may be lighter - 8lb vs a 10lb spring but . . I honestly couldn't tell by hand. What it most definitely is - is shorter. I'm at work now and I did this 3 or 4 days ago so I don't have either of the springs handy but from memory -- I'd say the hill one is . . 1/2" to even 3/4" inch shorter. ( I don't think it is more than an inch ) Cutting to the chase - the gun is now quite "dialable" via the HS - I have been able to dial it back up to the 955'ish fps speed that it prefers for those slugs and . . . . yeah - it may be a little quieter. That m-rod has never really been noisy anyway. I've yet to run it beyond 3 magazines as yet to see if fuel efficiency has in fact changed.

Regardless - it hits critters hard and is really accurate - so I'm good with it. ;-)
 
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Hi guys . . .

I did put the lighter spring in it (the Tim Hill one) and upon doing so first impression when comparing it to the OEM one is not so much "lighter" to compress in hand ( squishing it together using pointer finger and thumb ) - that "measure" seemed to me anyway - hard to tell. It may be lighter - 8lb vs a 10lb spring but . . I honestly couldn't tell by hand. What it most definitely is - is shorter. I'm at work now and I did this 3 or 4 days ago so I don't have either of the springs handy but from memory -- I'd say the hill one is . . 1/2" to even 3/4" inch shorter. ( I don't think it is more than an inch )  Cutting to the chase - the gun is now quite "dialable" via the HS - I have been able to dial it back up to the 955'ish fps speed that it prefers for those slugs and . . . . yeah - it may be a little quieter. That m-rod has never really been noisy anyway. I've yet to run it beyond 3 magazines as yet to see if fuel efficiency has in fact changed.

Regardless - it hits critters hard and is really accurate - so I'm good with it. ;-)
Click to expand...

That's exactly what should have happened, glad you got it figured out. Now IF you wanted to get it running the best it possibly could, at 955fps, here is what I would do. Crank hammer spring all the way in. Turn the reg up a couple bar and try it till you get a reg setting that gives you 985 fps. Then leave it at this reg setting and turn the hammer spring back out till you get to 955. This will put you just below the knee of the reg/hammer velocity curve.
 
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BigTinBoat,

You are correct, to a point. I meant with what he had installed, it wasn't going to get more efficient. If you crank the hammer spring up, and nothing happens, and up the regulator, and there is no change still, it's the transfer port that needs to be larger. When one ups the reg, and no change in power occurs, that's a telltale sign of a flow restriction.....transfer port.

When the spring is changed to a shorter spring, it acts like a hammer denounce device.....sort-of. Being that the hammer spring is shorter, the hammer free floats a bit, and doesn't have the chance to bounce back and forth as much. It does a little bit, but it's negligible.

As far as fine tuning it is concerned, what you described above would be the proper way to get the most out of it.

I'm an advocate for opening up the transfer port bushing to the max, and opening up the metering screw on the right side of the valve. On all of my tunes, that's usually the first thing that I do, then I go from there. Sometimes after it's tuned after that, most of what you described above, you can retain the same velocity by turning the reg back down, saving more air, and being more efficient 

Tom Holland 

Field Target Tech 

Fieldtargettech.com 
 
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