When is a Marauder .. no longer one ? ... it becomes this exotic Monster

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Motorhead

Motorhead

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Nov 1, 2018
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California, United States
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This was a fun project that has been in the works for well over 2+ years now. all the parts and pieces acquired at minimal cost in trades and bargain hunting, most of the exotic stuff self fabricated in house. All said for the rifle minus optics less that a few 100 dollars invested ... Just a lot of time which is free.

After recently having a gracious GTA member do the final machining on the main air tube, all the parts and pieces stashed away could get assembled. Into the mix some modern Tech as well making for a rifle that LOOKS LIKE an M-rod but ONLY used 3 OEM parts
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Those being a partial & re-machined steel Air tube, Trigger group and Stock. EVERY OTHER PART is something custom or one off exotic / prototype.

Inside this beast sits one of my custom balance valves ( actually this one ) with the reversed thimble & external spring. Transfer port is a TAPERED design reducing the output end for increased throat back pressure and faster poppet closing. * tested & proven effective in a previous thread.

Hammer is a buffer type of my own design having an adjustable peek striker thrown at the valve via an External SSG devise where screw protrudes out the back of adjuster when cocked.

Air tube at a length providing @ 80 cc of plenum then a WAR drop block. 500cc 3K aluminum tank with a prototype adjustable output regulator provides the required HPA.

Up on the upper receiver sits a JSAR side lever breech with a full length @ 23.7" LW Poly barrel in .25 caliber. Custom shroud, end cap screwing on placing the assembly into tension being Super stiff and no wiggle !

Stock was cut out as needed for the regulator and kept long on the right side, shortened on the left for gauge & adjustment access. All done painted in Rustoleum textured along with shroud tube.
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Performance wise it took a bit of trial & error in getting the hammer strike correct in not only stroke but hammer weight. The buffering aspect of hammer while not active keeps the valve lift in check providing a few more shots off reg without valve over dwelling. Total hammer weight @ 37 grams and stroke @ 3/16" less than OEM spec maximum.
This rifle was conceived and set up to be a Pellet shooter leaving the slug duty to my WarP .22 ( Another thread ) In my extensive testing with the LW Poly not only were JSB 25.4 Kings happy at +/- 1000 fps from it, the Benjamin 28 grains were too at 960/970 with JSB 34's trucking along in the upper 800's. This on 2000 psi set pressure leaving me with 1000 psi to play with on the 500cc tank.

Here is where rubber meets and road sort of speak .... Having a very blended array or technologies many of us have seen these past couple years, some fortunate to work with
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has been married into this build with the results being pretty darn astounding IMO.

As you see the gun with the spec parts mentioned, shooting the Benjamin 28 grain dome pellet at @ 960/970 fps guns cruising along at an easy 58 ft-lbs. Accuracy at 80 yards is inside a QUARTER coins group if I'm doing my part. ( not going to share groups or entertain such look at this silliness ) 
Last full tank string of shots taken started at 3000 psi and after @ 62 shots both gauges were at 2K and just showing movement lower. * So were seeing 62 shots on 1000 psi off a 500cc bottle.

The numbers using Lloyds calculator has it at: avg FPE/cuin per shot 1.72 with avg PSI used per shot 16

Damnnnn I'll take that too the bank any day, any where !!

As too if or not there is more power available
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.... ABSOLUTELY being just a matter of pressure increases and adjusting hammer strike to match.
Well now I know I've built a worthy platform that with a barrel swap to unchoked could, would be an AWESOME slugger ... or just leave it be as the SLEEPER it appears to be
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Thanks for following along,
Scott S


 
I'm curious though about your hammer design. How does it work?
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Only picture is that of it's prototype .... This version shown is an extension assembly screwed into the hammer strikers 1/4-28 threading.

The length of the extension is that of the reduced amount of stroke. ( this hammer was for the WarP .22 slug gun which has a longer stroke than a M-rod.)

With the latter buffer hammer used in the above build, hammer is one piece with the @ 3/16" extension built in. Retractable strike tip in PEEK remains and no longer is there an o-ring for contact against valve body. Current hammer is MDS nylon and just let it contact the valve body if and when that happens. * also less bounce reactive than the poly o-ring. ** valve is a modified WAR

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On the end of the extension ( Buffer end ) sits a retractable strike tip that when dropped below flush will create contact of the outer most area of the extension to the back of the valve body at some point further it is retracted. Ideally set based on hammers weigh, spring energy driving it etc ... the poppet is pushed in and buffer adjusted so when poppet lift naturally stops the contact with valve body is just shy of happening. When you come off the reg set point and valve starts opening easier you start bottoming out against the valve body and poppet lift is limited. This keeps the valve from over dwelling and buys you some shots under the regs set point.



Understand that BALANCED valves don't really respond like a conventional knock open valve where a bell curve with pressure can be established nearly as easy.

In most instances hammer weight in use is in excess of what really required with finely tuned set up ... The heavier ( Over weight ) hammer allows a very broad power range and pressure the valve will process & use of a buffering system is a crutch that allows it.

* While guns operates currently with 37 grams of hammer weight ... I can & have at the same power W/O the buffer run with a hammer of just @ 26 grams and gotten a very similar tune. Sadly doing so getting MORE power is difficult because there simply is not enough mass to open the valve at a high reg set point with less weight.



Always a compromise somewhere, this is no different.



Scott S
 
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Hey Scott, did you modify the factory valve body or did you make one from scratch? Curious on the material used. I'm finding that I like this hard Ketron PEEK for my valve poppets, but I can't use anything harder than 360 brass for my valve bodies (485 brass is tough to get a perfect seal with that PEEK material). 

I'm prototyping some balance valve designs for a couple of my PCPs - similarly, with plans for SSGs, adjustable throw hammers (and some other completely whacky ideas that may or may not work 🙃). Are you getting any hammer bounce with this setup (and is it worse at lower reg pressures)?
 
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Hey Scott, did you modify the factory valve body or did you make one from scratch? Curious on the material used. I'm finding that I like this hard Ketron PEEK for my valve poppets, but I can't use anything harder than 360 brass for my valve bodies (485 brass is tough to get a perfect seal with that PEEK material). 

I'm prototyping some balance valve designs for a couple of my PCPs - similarly, with plans for SSGs, adjustable throw hammers (and some other completely whacky ideas that may or may not work 🙃). Are you getting any hammer bounce with this setup (and is it worse at lower reg pressures)?
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As to balanced valves and all the variants I've fiddled with, balance ratios etc .... have been using a recycled valve body. Done m-rod valves, SS1 & SS2 bodies and well WAR bodies.

some have been on aluminum seats with delrin poppets, some peek too tho much trickier to get sealed especially at lower pressures or balance ratios.

My most desirable is using WAR valves with there Stainless seats with peek poppet.

In ANY of the configurations if and when you can get a good seal and gun will fill and not leak .. YOU WANT TOO use an SSG or free flight hammer staying away from any poppet stem preloading.

SSG's work IMO far better than free flighting with a slack spring. Every case I've experienced with uncontrolled jack hammering has been when a free flight spring or a very soft SSG was used and when hammer was sent back upon poppet closing there was enough bounce to get valve to fire again again again .... That sucks !!



Hope this help you,

Scott S
 
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Here a picture of a Balanced converted WAR valve using a PEEK poppet looks like. * This built on the typical design of the poppet head having an opposing "male" end up into a "Female" thimble. Picture up above of the INVERTED redesign has the thimble as the backside of poppet head and the male portion with the o-ring fixed to the intake grate.



The latter can create a smaller volume balance chamber because the spring is external to the chamber. Also the o-ring that seals the chamber to poppet no longer has the vent hole passing threw the root diameter of the 0-ring groove.



In Function they operate similar given the same balance ratio of Poppets sealing diameter to the seat and that of the balance chambers diameter.





TMI for some ... food for others !!!



Scott S







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Well time for an update after @ 6 months of barrel/caliber swaps, valve & hammer tweaks etc ....

Today no more screwing around with the smaller calibers in this monster having put back in the LW poly .25 we started with.
Last we were fooling with it the valve was back to a large balanced configuration, original hammer short stroked and tapered transfer port.
Adjustable regulators set point tho sitting on @ 2400 psi and we have a 480cc CF 4.5k bottle fitted now.

Get it sighted back in at 50 yards just to see how it shot ? ... Wow really really hard shooting both Kings and King heavies @ quarters diameter off shootin sticks and a stool. Too much recoil to be real steady, so likely more accurate than i was seeing.

CHRONY .... JSB 25.4 kings @ 1010 fps @ 57.5 ft lbs !! with the king heavy 33.95 @ 935 fps !! At a whopping 65.8 ft lbs power !!

Had figured early on just a matter of pressure to find more power ... Yea no poope !!

Scott
 
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What's the size of your barrel and transfer ports? Pressure isn't the only solution for power. I'm getting 965fps with 33.95 heavies at 2000psi from modified WAR cobra valve. Stock marauder barrel with about .21 barrel port. And there's still a couple of improvements to be made. This tech is not at it's peak yet. Not even close.
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I would say YOU HAVE NOT read the entire post ... have no clue gun can be cocked with your little finger ... very very quiet ... stellar air efficiency.

And this build has never been about seeking Maximum power ... but utilizing some new tech to make a gun that is a superior user experience in not only operating it but having such low cyclic vibration shooting it. The accuracy too exceeds a heavy hammer, heavy sprung conventional configuration you describe owning.

Never has it ever been said that balanced valves would or even could exceed or even make the power of a conventional valve ... what power they do make comes a lot easier mechanically making for a much more docile shooting gun. Use a lot less air in general for equal power ( Higher power levels ) and can set up at these higher power levels to have greatly improved efficiency.

Power comes from the PRESSURE and ability to deliver it as quickly as one can behind said projectile before it's motion down barrel starts. All the rest is TIMING of how the pressure gets there, how quickly it peaks and then collapses when adding more air flow no longer buys you any power/speed.



Different miens = differing shot profile etc ...




 
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UPDATE ....
Bottlerauder is now set up as a .22 using a 23" HW 6 groove No choke barrel shooting in the @ 47-48 fpe range which does heavy pellets and 23-25 grain slugs excellent !! It is IMO the ideal balance in power and air use for this rifle. * can be turned up to shoot harder, but as set is in the sweet spot. Efficiency remains outstanding !


 
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