Mrod reg

[FuzzyGrub]

I believe the TSS has a nylon tipped set-screw for locking down the adjustment, so you should be fine. 

[shorty]

This is a pretty good read here about how the 40/40 tune or more can be achieved on your 25 cal.

https://www.gatewaytoairguns.org/GTA/index.php?topic=116706.0

[dpittman]

Paul, I have no mods at all. I think my settings are hammer spring 3 turns clockwise and striker all the way ccw. I think my vms is open all the way. Hope this helps you some. The king heavy pellets at only 725 are a little too loopy that is why I want to boost the speed s little.

[int3man]

I'm not comfortable enough, nor do I have the self confidence to start modifying the stock parts!  I have no idea the weight of the Hammer.  I got it from Rocker1 right after I bought the rifle because I was told it was a must have!  LOL!  The more I read different posts about tuning, the more confused I become.  I want to learn, but it sure would be nice if there was an instruction manual that gave some common settings to try first and then adjust from there...

This is where I'm at now...  I closed the Velocity Port on both rifles and then opened them a full 5 turns.  On the .22 I brought the striker all the way back next to the body of the hammer and backed the hammer spring all the way out and then went to shooting and adjusting over the chrony.  I have that one sitting right at 900 fps using JSB 15.98 gr pellets, so I'm happy with it.  I't bone stock except for the regulator that is set at 2000 psi.

The .25 is another story.  Did the same thing but the best I can get is 725 fps with JSB 25.39 gr pellets.  I'm kind of disappointed in the results and am thinking of removing the MDS Hammer and the TSS and going back to stock and see what happens. 

I don't know if I fully understand the function of the TSS, but it's almost as if the adjusting screw should be twice as long as it is.  Twice I adjusted it to the point it went right through and then I had to disassemble the rifle to get it threaded back into the back piece.  I thought the idea was having two springs that could be adjusted independent of one another, but it appears the adjuster pushes both springs equally.  Or at least they do when I'm at a point where the rifle is making more than 500 fps!  If the adjuster is just moving the inner spring, the rifle is producing less than 500 fps...  I'm not sure if it will work, but maybe I'll try replacing the outer spring with the stock spring and see what happens... 

My goal was to get between 800-850 fps, but as it sits it doesn't appear to be capable of producing that output...

UPDATE: I swapped hammer springs and put the stock hammer spring in the TSS and have been able to get a pretty consistent 800 fps from my .25 Mrod.  Still thinking I need to do something different, but for now, it is workable...

Hi Well my 2 cents worth.  You got the Hammer from Rocker1 and he is in Florida, so I would go back to him and have him tune it for you.  He has all the tools to what you need for your rifle.  Open up the Barrel TP and make you a .187 TP  you'll be in the 800 with the TSS and the light weight hammer.  40 / 40 is readily available on the MRod's.

Michael :- )

[Rat Sniper (AKA: PaulT58)]

Well, I put it back to stock with the exception of the regulator and am getting 820 fps using 15.89 gr pellets.  Seems the TSS and MDS Hammer are more for lower power higher shot count applications. 

If I lived closer to David, I'd definitely drop it off and have him work his magic, but I'm not a big fan of the Postal System, UPS or FedEx, and don't want to chance it getting mangled while in transit...

[AlanMcD]

I have Huma regulators in both a .22 and .25 Marauder.  I have the .22 and .25 plenums with the built in gauge port, as well as the XXL tuning plenum that is used with the existing gauge port.

The plenums with the gauge port can be modified with a Dremel to hog out unneeded aluminum, as the material for the gauge port forms a full “ring” inside the plenum for easy manufacturing.  Doing this will add about 6ccs of plenum space.  See the picture to understand what I am referring to here (and no comments about how ugly I made the part – it is functional    ).

The plenums have the following lengths and volumes (as measured by the water that they hold, measured up to the threads that the regulator mounts to, in a graduated cylinder):

.22 plenum: ~11 ccs, ~17 after mods, 56mm long (not counting regulator)
.25 plenum: ~16 ccs, ~22 after mods, 70 mm long
XXL plenum: ~28 ccs, 85 mm long
Gauge port: ~2.5ccs, ~8 after mods, ~35mm long (if I recall correctly, as it is in the gun now)

Most valves probably have around 5 ccs of volume within them, thus – assuming we mod for more plenum space – we have the following approximate plenum sizes in the different set ups:
.22 regulator:  ~23ccs
.25 Regulator:  ~27 ccs
XXL by itself:    ~33 ccs
XXL with gauge port: ~42 ccs

There is probably another cc or two that comes when the regulator is threaded into the plenum, but all these values are good for comparisons to each other.

As for performance, you can definitely get where you want to go, but you may need to install one of JSAs new SS valves.  Prior to switching to this valve, I ran a modified stock valve and the .25 cal modified plenum, and with the regulator set at 2100 psi the best I could shoot the 34 grain pellets was about 775.  With the SS valve and that same plenum / regulator setting I could hit about 820 fps for 20 shots with an ES of 2%.

I switched to the larger plenum, and even though it ate up 2” more of my HP reservoir space (I figure I am at ~150 ccs now and was at ~180 before), I found I now get 20 shots at about 850 fps with the same 2% ES (just 1.2% ES if I limit it to 16 shots or two full mags).  It turns out that it actually uses less air per shot with the large plenum shooting at 54 FPE than it does with the smaller plenum shooting at 51 FPE – that is the level of efficiency gain that comes from the larger plenum.  I won’t know how I end up tuning mine until I can get to testing the accuracy at longer ranges (plus I have a longer lightweight tube on order that will more than recover the volume lost in the reservoir from the larger plenum).

I think if I dial back the speed to 800 fps with the 34 grain pellets, I could get to 25 shots, but I doubt 30 at that power (at least not without the longer air tube).So you can get where pretty much where you want to go, and the best path there for that high power set up would be with the XXL plenum and a hogged out gauge port (or Hill high flow one) and a new SS valve with the right flow path (I run a 0.190” transfer sleeve and barrel port). . . .

[dpittman]

So assuming no machining on stuff which setup has more plenum. Huma reg with gauge port or standard Huma reg and Hill gauge port.. I don't want to be tearing down my gun every day to "try" stuff. Wanna get it right  the first or second time.

[squirrel_hunter]

Well, I put it back to stock with the exception of the regulator and am getting 820 fps using 15.89 gr pellets.  Seems the TSS and MDS Hammer are more for lower power higher shot count applications. 

If I lived closer to David, I'd definitely drop it off and have him work his magic, but I'm not a big fan of the Postal System, UPS or FedEx, and don't want to chance it getting mangled while in transit...

I have shipped a box(same box)with Mrod action to 0utlook Washington from 0hio 7-8 times with zero damage.protect the trigger and pack box correctly and you will not have a problem.i always insure package and have it marked fragile...as a matter of fact I getting ready to send another Mrod action that way for light air tube and regulator.

[Rat Sniper (AKA: PaulT58)]

So assuming no machining on stuff which setup has more plenum. Huma reg with gauge port or standard Huma reg and Hill gauge port.. I don't want to be tearing down my gun every day to "try" stuff. Wanna get it right  the first or second time.

LOL!  Good luck with that!  I have the Huma Regulator with the Gauge port, so it seems I would need to enlarge the inside to get more volume.  I'm not comfortable with that, so I'm kinda stuck right now.  The Hill Gauge Port would give you more volume after the regulator, but I believe that would come with a loss of stored air volume in the tube since you are introducing another component that takes up space.

I just ordered a lighter valve spring and a .161 TP from Hill to see if that will help.  I removed the TSS and MDS Hammer yesterday and put the stock parts back in.  I can now get 820 fps out of the 25.39 gr pellets but for only about 15 shots on the regulator.  I'm hoping the lighter valve spring will work better with the MDS hammer. 

I'm not so sure about the TSS.  To make any sort of power with it installed, I had to increase tension on the hammer spring to the point where the adjustment screw went completely beyond the threads, which resulted in tearing into the rifle once again to hand thread it back together so I didn't cross thread it trying to back it out.  I might look for a longer adjustment screw and try it again.

[Rat Sniper (AKA: PaulT58)]

Well, I put it back to stock with the exception of the regulator and am getting 820 fps using 15.89 gr pellets.  Seems the TSS and MDS Hammer are more for lower power higher shot count applications. 

If I lived closer to David, I'd definitely drop it off and have him work his magic, but I'm not a big fan of the Postal System, UPS or FedEx, and don't want to chance it getting mangled while in transit...

I have shipped a box(same box)with Mrod action to 0utlook Washington from 0hio 7-8 times with zero damage.protect the trigger and pack box correctly and you will not have a problem.i always insure package and have it marked fragile...as a matter of fact I getting ready to send another Mrod action that way for light air tube and regulator.

I'd definitely insure it!  Do you ship the entire rifle, or do you remove it from the stock and just ship it without the stock?  That seems like it could help reduce shipping costs some.

My other issue is the want to learn.  If I ship it to someone else, I don't have the opportunity to learn how to do it myself.  To me that's part of the fun of owning an air gun.  It can also be a frustrating part, but by doing it myself, I hope to gain the confidence to try new things later on.

[triggertreat]

FWIW, my standard .25 Huma, Hill gauge port and SS valve gives me 34ccs all together.  I ran multiple fluid test to verify this.  This is without any kind of mods to them.

[AlanMcD]

dpittman,

I really don't know the volume of the .25 cal tuning plenum - by the pictures, it clearly looks shorter than than the one with the gauge port so they probably are trying to equalize the available plenum volume between the two.  However, we can't tell if they are equalizing the volume without the gauge port or with the gauge port (most likely with the stock gauge port).

My guess would be that you will get the most plenum volume from the tuning plenum and a hogged out or Hill gauge port, but if you really want to know you can ask them from their contact page on their website - they are good about answering questions.

As Paul said, the tuning plenum and gauge port together will take up more of your reservoir space, reducing the high pressure air available to fill the regulated air space.  All things being equal that would reduce the shot count, but when shooting at high power you need more plenum space to shoot efficiently.  I have found that the efficiency gains more than offset the lost reservoir space - but you have to gain the plenum volume for that to work.  If you lose resevoir volume without gaining plenum space that would just be bad.  In my specific case I gained about 15 ccs of plenum with the XXL tuning plenum at the cost of  about 30ccs of reservoir space but still came out ahead in terms of shot count at power through the efficiency gains.

Paul,

I have had no issues with getting power with the TSS - set up right, it can actually increase hammer strike energy simply because it has two springs in it.  I love mine, and I actually use it as a simple two power level adjuster in mine (full out to full in on the inner spring).  I suggest trying different springs in it if you can't get enough power.

[AlanMcD]

That is the perfect bit of missing info Keith!

So it looks like ~41 ccs with the XXL tuning plenum and a Hill gauge port, and ~34ccs with the .25 tuning plenum and the Hill gauge port.  Neither of us have tried both, but they both will work for what you want.  Worst case, Huma does sell the plenums separately for about 35 euros if you ever want to change things up.

There really are no mods that you can do with the tuning plenums as they are already maxed out on volume for their length.  The mods really only apply to the plenums with a gauge port, and to the stock gauge port if you don't want to buy the Hill one.  I have one similar to the Hill port (I think it came from Addicted to Airguns many years ago, and I modded the other myself (it is easy with a Dremel and a metal cutting bit - just carve out the excess).

[FuzzyGrub]

Alan and Keith,

Thx for posting the plenum info.  I was toying with the idea of a reg'ed Mrod at 55FPE with the 34g JSBs.  Looks like that would drive a larger plenum than I have and probably not achievable with a mod'ed oem valve. 

[AlanMcD]

John,

You can get there with the JSA SS valve - that thing is amazing.  I tested it without the regulator and I had no problem pushing the 34 grain pellets over 1000 fps.  I did not leave it there as the accuracy is probably lousy, but someday in the summer I may pull the reg and test it at those speeds at distance just to see what it does. 

At the other end, I was able to tune for a decent string with the 25.4s at around 850 fps.  It is amazingly versatile . . . . but a little complicated to get your head around with the jet changes too.

[triggertreat]

Alan and Keith,

Thx for posting the plenum info.  I was toying with the idea of a reg'ed Mrod at 55FPE with the 34g JSBs.  Looks like that would drive a larger plenum than I have and probably not achievable with a mod'ed oem valve.

I don't know, if you can get all the ports to 3/16" and enough flow through the valve you just might hit that power level.  I think the only difference might be the reg set point and possibly the cocking effort.

[shorty]

This is what your expectations should be in 25 cal. Stock modified valve with standard Huma with gauge port and ultra modified valve with modified gauge port huma reg. Stock hammer,stock barrel length.

This is not for bragging or anything like that. This is what you should expect if not better from purchasing parts since mine were all done in the garage.

Reg setting is at 2050 psi

[squirrel_hunter]

Well, I put it back to stock with the exception of the regulator and am getting 820 fps using 15.89 gr pellets.  Seems the TSS and MDS Hammer are more for lower power higher shot count applications. 

If I lived closer to David, I'd definitely drop it off and have him work his magic, but I'm not a big fan of the Postal System, UPS or FedEx, and don't want to chance it getting mangled while in transit...

I have shipped a box(same box)with Mrod action to 0utlook Washington from 0hio 7-8 times with zero damage.protect the trigger and pack box correctly and you will not have a problem.i always insure package and have it marked fragile...as a matter of fact I getting ready to send another Mrod action that way for light air tube and regulator.

I'd definitely insure it!  Do you ship the entire rifle, or do you remove it from the stock and just ship it without the stock?  That seems like it could help reduce shipping costs some.

My other issue is the want to learn.  If I ship it to someone else, I don't have the opportunity to learn how to do it myself.  To me that's part of the fun of owning an air gun.  It can also be a frustrating part, but by doing it myself, I hope to gain the confidence to try new things later on.

send just the action.i have a couple of air rifles that way I can work on one and still have some to shoot...

[dpittman]

This may sound like stupid question. Can you have too much plenum in a regulated gun. I see Huma has a .30 XXL plenum. If I was desiring about 50 fpe with jsb 33.95 mkII in my mrod would it be necessary to have this or stick with standard .25 reg. With the larger plenum could you have a lower set point to get higher power.

[triggertreat]

This may sound like stupid question. Can you have too much plenum in a regulated gun. I see Huma has a .30 XXL plenum. If I was desiring about 50 fpe with jsb 33.95 mkII in my mrod would it be necessary to have this or stick with standard .25 reg. With the larger plenum could you have a lower set point to get higher power.

You can easily hit 50 FPE with the standard .25 version as long as the ports are opened up and you have the correct set point.  The larger 30 cal plenum will just make it a little easier to do with the added volume.