Putting the squeeze on the Mrod - Aftermarket Valve inquiry

[Precision Action]

Originally wanted a jsair SS balance valve, but Jsair went through a period where they were moving shop and were down for a while. So, when it came time to order parts for my Mrod, I went with Don Cothran's powerhouse. After all, Don does impeccable work, probably the highest grade machined parts I have seen. I still have to work out some kinks on my rifle, and have had some difficulty getting it tuned. I don't think my plenum is large enough to handle the powerhouse valve, which opens up like a bass fish gulping its prey. In order to get more shots out of my rifle, with external bottle attached, I am going to have to cut the regulator down to around 147-149 bar, is what I figured. Velocity is completely not impressive, at 787 FPS. (AND yes, my .22 Diana 34EMS is only a smidge slower.)

So, would jsair's ss balance be more efficient with air consumption versus delivery? Or would it not matter?

Also, has anyone purchased an aftermarket barrel for their Mrod that is longer than the stock barrel? Thinking a longer barrel would help increase velocity without burning through my air supply.

[Hobbyman2007]

There definitely something wrong if all you are getting is high 700’s. Do you know how big the plenum is in your rifle? I would think that is the holdback if not it could be the porting. In most cases when trying to achieve max power regardless of valve used , big ports ( bore size) and at least .5cc per desired FPE of plenum is needed.

[PikeP]

If you left porting stock (.14" transfer port or barrel port) then high 700's is actually normal for a 34 gr in a stock .25 cal regulated marauder at 147 bar. Mid-low 800's for 25.4...


Valve type does NOT GIVE or TAKE power, what they(balanced valves) can do is allow you to operate the valve with less hammer energy, but they will not output more energy than its stock counterpart.

I would avoid all balanced valves in your Mrod personally, and sell the cothran valve, unless you plan on .30 + cal and gobs of power...in fact, just sell it all and buy a 1k mid-level gun that has all the bells and whistles and shoots at the power level you want in stock form

Your gonna find yourself in a money pit...now if you have money to blow, by all means feel free.

Alternatively, port the rest of the air path (transfer port + barrel) to around .1875" or so, and tune your hammer weight + spring so its not wasting air and leave it be.

[fatmike]

I have 3 marauders I bought as parts guns. I plan to modify them to be regulated 40/40 tuned guns. I'm not planning on much more then that or the money spent will be well over what the guns value to me is. I plan to open the airway and use a lighter hammer to begin with and see where I'm at.  The parts for marauders arent as available or as inexpensive as they used to be.  Anything over 450$ with the gun included I can just buy something manufactured to the better specs.  It's fun to tinker but I want to remain above water with it. So many lo cost airguns available today.

[Mr Fluffy Tail]

i went with the Hill valve hammer and spring, its sold as a pretuned set, 'and' i used a hill machined depinger so .. its not the plenum size ..likely the hammer, spring, and the port needs to be larger ... Hill uses a high prssure fuel straw to replace the tf port and the barrel port is drilled and cleaned up with a burr ...  but it did 900+ with 34s easily ... theres spring adjustment left to go even higher ..

[Frank in Fairfield]

Fun to read about tuning.
I have three Gen I Marauders in the three calibers.
Motörhead did his thing on the .177 but the other two, save the lawyer spring removal, are untouched..
They shoot fine..

[AlanMcD]

I have three Gen I Marauders - my first was a .22 from 2010, then added a .25 in ~2016, and then built a bottle-rod out of extra parts last year.

Back in those "early" days there weren't that many other great options out there for the money, and that was the heyday of M-Rod custom parts availability.  Basically the only thing "factory" on my guns anymore are the breech blocks, trigger groups, and fill ports.  Lots of time and money spent on them over the years improving them - the time is irrelevant as it is a hobby, but the money is real.  The first one in the stable probably ended up costing me close to $900 before I was done (although the parts keep bouncing between guns - I think of them as my adult Mr. Potato-head set).

I have no real regrets, as it was the best thing to do then, and I could not afford to drop all that coin at once and did not want to wait five years or so to buy my first PCP.  But I will say that I did eventually buy a used Daystate Air Ranger for not much more than I dropped into that first M-rod, and there is no comparison - as much as that custom M-rod (with Boyds stock with custom cheek riser) was nicer than a factory M-rod, the Daystate is about that far ahead of my custom M-rod . . .

Bottom line, all of this is just an example to reinforce what Matt and Mike said - these days, it is not worth going there.  There are better guns available for less money than you will put into the M-rod, and you won't ever get it back out (but as suggested, probably the best return would be to sell the Cothran valve out the gun, as those are still in demand).  The Marauder is still a solid gun to own, but any money spent on customizing would probably result in "less gun for the money" than you can just go out and buy today (unlike 5 years ago).  But if you feel you have to keep at it, I get it . . . 

[Precision Action]

There definitely something wrong if all you are getting is high 700’s. Do you know how big the plenum is in your rifle? I would think that is the holdback if not it could be the porting. In most cases when trying to achieve max power regardless of valve used , big ports ( bore size) and at least .5cc per desired FPE of plenum is needed.

Every time I go and shoot, I connect my mrod to a Scott safepac to ensure I have plenty of air for whatever. My velocity measurements came from a session where I was needing to run some tests and re-zero out my scope. For that session, I shot H&N field target trophy, because they are uniform, and I rather consume them for tests than slugs, slugs get pricey. Here are the stats:

Pellet Grain: 20 gr
Plenum Size: 30 cc
Muzzle Velocity: 787 FPS
Tank Pressure: 200-185 Bar
Regulator Pressure Setting: 155 ~ 160 Bar
Current FPE: 27.51 FPE

It does appear there is something reducing the efficient operation of the rifle, not sure exactly what.

[sb327]

Don’t these have a screw under a screw tp adjustment? Might be worth checking.

Dave

[kkarmical]

There definitely something wrong if all you are getting is high 700’s. Do you know how big the plenum is in your rifle? I would think that is the holdback if not it could be the porting. In most cases when trying to achieve max power regardless of valve used , big ports ( bore size) and at least .5cc per desired FPE of plenum is needed.

Every time I go and shoot, I connect my mrod to a Scott safepac to ensure I have plenty of air for whatever. My velocity measurements came from a session where I was needing to run some tests and re-zero out my scope. For that session, I shot H&N field target trophy, because they are uniform, and I rather consume them for tests than slugs, slugs get pricey. Here are the stats:

Pellet Grain: 20 gr
Plenum Size: 30 cc
Muzzle Velocity: 787 FPS
Tank Pressure: 200-185 Bar
Regulator Pressure Setting: 155 ~ 160 Bar
Current FPE: 27.51 FPE

It does appear there is something reducing the efficient operation of the rifle, not sure exactly what.

What are the numbers without the regulator?

[Precision Action]

What are the numbers without the regulator?

Sorry for the late response, I had to spend some time in developer land working on plugging a vulnerability.

It is going to be rather difficult testing that one out at the moment. I do not remember how exactly it happened, but at the moment the pressure gauge manifold is leaking air like something crazy. It busted both orings, and I have yet to find one that seals it correctly.

But on the good side of things, I swapped out my home made SSG for one fabricated by JSAIR, and after some adjustments was able to get an additional 5 meters per second out of it. Not home yet, but getting there.

Does anyone have any experience with Nielsen 25 caliber 34.5 slugs? I went from shooting JSB slugs to the Nielsen, and the result was shotgun spray.

[Motorhead]

What are the numbers without the regulator?

Sorry for the late response, I had to spend some time in developer land working on plugging a vulnerability.

It is going to be rather difficult testing that one out at the moment. I do not remember how exactly it happened, but at the moment the pressure gauge manifold is leaking air like something crazy. It busted both orings, and I have yet to find one that seals it correctly.

But on the good side of things, I swapped out my home made SSG for one fabricated by JSAIR, and after some adjustments was able to get an additional 5 meters per second out of it. Not home yet, but getting there.

Does anyone have any experience with Nielsen 25 caliber 34.5 slugs? I went from shooting JSB slugs to the Nielsen, and the result was shotgun spray.

34.5 slug in a 20" Marauder barrel at the power most M-rods shoot at ... IMO Way Too Heavy a slug !!
That weight and speed required to really get any accuracy / performance would require that rifle running in the 60+ FPE range

[Precision Action]

If you left porting stock (.14" transfer port or barrel port) then high 700's is actually normal for a 34 gr in a stock .25 cal regulated marauder at 147 bar. Mid-low 800's for 25.4...


Valve type does NOT GIVE or TAKE power, what they(balanced valves) can do is allow you to operate the valve with less hammer energy, but they will not output more energy than its stock counterpart.

I would avoid all balanced valves in your Mrod personally, and sell the cothran valve, unless you plan on .30 + cal and gobs of power...in fact, just sell it all and buy a 1k mid-level gun that has all the bells and whistles and shoots at the power level you want in stock form

Your gonna find yourself in a money pit...now if you have money to blow, by all means feel free.

Alternatively, port the rest of the air path (transfer port + barrel) to around .1875" or so, and tune your hammer weight + spring so its not wasting air and leave it be.

I appreciate the advice and agree, in the long run, it would be more fiscally responsible to make a larger initial investment in an air rifle, rather than attempt to fiddle, piece together, and patch a lesser expensive rifle into something a user would be happy with. Although, the latter is easier due to contingent restrictions. The MRod is my first venture into PCP, and after my time shooting air rifles I still have reservations spending more for an air rifle than I would for a powder burner.

As for porting, I do not own a drill press, and would hate to attempt to port anything without one. It is not the same thing by any stretch of the imagination, but Cothran does provide a transfer port adapter for 25 cal, which I already have. My inquiry about the jsair valve, was more or less, an attempt to settle down any regrets I may possess.

[Motorhead]

.25 using a Cothrin ... Transfer path all the way too and including barrel @ .180" diameter

[Precision Action]

34.5 slug in a 20" Marauder barrel at the power most M-rods shoot at ... IMO Way Too Heavy a slug !!
That weight and speed required to really get any accuracy / performance would require that rifle running in the 60+ FPE range

OK, I will come off the grain some, look into something in the lower twenties and give it a try. It is a shame, though, I still have four boxes of 275 round Nielsen 34.9 remaining.

The reason I ask is that I was shooting JSB KnockOut Slugs .251 Cal 33.49gr and not doing too bad, but when I made the move to 34.9 Nielsen, all heck broke loose. It is only a difference of 1.4 grain.