Benjamin Marauder Workshop

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Benjamin Marauder Workshop

    The Benjamin Marauder is a multi-shot PCP manufactured by Crosman in the USA - It is an accurate and good value PCP that lends itself well to tuning and home maintenance.


    Chapter 1
    The Australian Issue M.rod

    My own rifle was one of the first shipments imported into Australia through Ausarms in Sydney.
    The rifle in question although completely safe and compliant in most other first world countries is subjected to several questionable alterations to satisfy the notoriously over-zealous firearm safety laws currently foisted upon the people of Australia.

    The main differences between a `Rest of the World` M.rod and the ones that we get are thus:

    Firstly the perfectly weighted OE hammer spring has been replaced for one that is thicker and stiffer - The reason for this rather clumsy alteration has something to do with getting the rifle through the ridiculous OTT Customs Drop Test – Whist this may put a big grin on John Howards face unfortunately it may well wipe the smile clean off yours as it does significantly increase the amount of effort required to cock the rifle.

    http://www.ebay.com/itm/Benjamin-Marauder-OEM-Hammer-Spring-177-22-25-/230937964199?pt=LH_DefaultDomain_0&hash=item35c4f9aea7

    The other BIG difference is the rifle`s bull barrel – The original M.rod has a air-diverted shroud along with a series of noise reducing baffles to make the rifle more environment friendly and safer to use for both the end user and any innocent bystanders – The Australian one...does not
    ---------------------------------------------------------------------------------------------------------------------------------
    Chapter 2
    Tuning

    My main concern was to achieve the flattest possible curve across the shot count - After much fiddling about on my one I found that with an OEM Hammer Spring Tension on 2 and Stroke on 2 near-as-damn gave me that result - If I wish to alter the velocity I only really need to adjust the Air Screw.

    At these spring settings on my gun I get these approx results on the Air Screw (Screw is turned out from fully in - Figures are Fps first and then Approx FPE using H&N FTT)

    V - 1 = 600Fps - 12FPE

    V - 1.5 = 700Fps - 16FPE

    V - 2 = 800Fps - 21 FPE

    V - 3 = 900Fps - 26FPE

    After much deliberation about power actually needed over shot count wanted I`ve finally settled on V - 2 which gives me 40 useable shots at about 20FPE

    -----------------------------------------------
    Another good tip for improving accuracy is to Float the Air Cylinder – This was one of Billy-Bush-Cooks ideas that I took on board and I found the improvement in accuracy is indeed noticeable.

    More of Mick`s excellent tuning advise can be found in the next post.

    --------------------------------------------------------

    Chapter 3

    Check Your Nuts

    Thought I`d let you know I`ve just had mine in bits again to make a quick fix on something that`s certainly well worth checking / addressing - The Hammer Stroke Screw - I noticed that during my last few sessions of target shooting the guns velocity was creeping up throughout the shot count with a progressively higher shot strike.

    I rechecked my settings (V = 2.2 - T = 2.2 and S = 2.2) and found that S had crept out to 0 - Weird but no big deal so I just wound it back in again and `away to go` - Next time out though exactly the thing happened.

    Now I seem to remember Mick had this problem happen once on his M-rod too so I didn’t really need to think very hard about a solution - So out with the Allan keys and strip down the action - Sure enough the Hammer Stroke Screw had worked itself loose again down to the end of its thread.

    A quick dab of Loctite firmly set the rascal back in its place and I soon had the whole thing back together again and shooting perfectly - Therefore if you ever have the hammer assembly apart for any reason I`d recommend taking the same precaution.
    -------------------------------------------------

    Chapter 4

    A Left Hand Conversion

    Even though Crosman do not offer this rifle for South Paw operation the action can be converted over with just a few DIY tools – The process to do this is shown below.

    The steel hammer chamber milled out from the original L shape to a T shape and the alloy action block grooved out to accept the swapped over bolt.



    The photo of the finished conversion at the bottom of the page shows the existing slot plugged with removable rubber grommet and covered with 6' Picatinny Rail to stop the bolt from lifting into the original slot whilst cocking - This also means the rifle can easily be put back to right handed again if need be.



    I know there`s always room for improvement but as a back shed conversion I`m pretty happy with the outcome – In actuality the conversion was so simple I can`t really understand why Crosman don`t offer a left hand model straight off the shelf.
    -------------------------------------------------------------------------------------------------------------------------------------

    Chapter 5

    The Bottle Brush De-Pinger post

    Here`s a new one to show you guys - It a great idea for a Fab, Cheap and Easy Depinging Device. />





    It came about when I helped a mate tune his M.rod to his own favoured specifications - ie: A Med/High power ratio with a nice rainbow curve and reasonable shot count - Which BTW was V-2.5 + T-2.5 + S - 2.5 returning a 835Fps average over 50 Shots 3000-1900Psi

    After we finished the chrono-string I suggested fitting a depinger `to put the icing on the cake` - Therefore after explaining the challenges of overcoming echoes and the condensation problems associated with current depinging devices my mate comes with this ripper of an idea which ended up working an absolute treat.

    I don`t think his missus was that impressed though as she`s now short of her brand-new kitchen bottle-brush

    Chapter 6
    Lothar Walther Barrel Upgrade

    For those of you who would like to try one Ausarms in Sydney can provide you with a replacement barrel for your M.rod made by the legendary manufacturer Lothar Walther - The barrel has been designed to `drop straight in` but I found it wasn't quite that straightforward and did have a couple of little challenges to overcome whilst shoehorning mine into place.

    The main issue I had was seating the barrel forward enough so I could get the mag back in the action - Every time I snugged the grub screws down it pushed the barrel back a bit too far. - I think LW might have cut the barrel locating recesses a little bit wider than the original resulting in a slight bit of play back and forth - Anyhow in the end I pushed a mag into the breech and put some lateral pressure on the mag whilst tightening everything down - that sorted it

    The other observation made is that the barrel itself has a tight tolerance size at either end but in the middle it has a tolerance of +0.1mm - I am reliably informed that the reason for this is that barrels don`t have to be super accurate in outside diameter over their full length and making them this way helps to keep the cost down a little Therefore if you do choose to change to one of these barrels the best way is to fit the shroud mounting bush from the breech end prior to securing it in the action,

    The other differences in the LW barrel compared to the Crosman one are the internal bore has wider rifling, less grooves and less of a twist ratio - Workmanship wise the bore seems smoother than the original and has a more precise crown - The choke is definitely shorter 1" on the Crosman and about 10mm on the LW.

    Ammo Test: LW Barrel

    Pretty much I`ve found that the LWB seems to like absolutely anything half decent that I push into it. and so far out to 55yds I`ve tried

    Air Arms Field Diablo (Heavies)

    H&N Field Target Trophy (5,5s)

    H&N Barracuda

    JSB Exact (Heavy)Crosman Premiers

    If I had to choose among the bunch I`d have to give it to the Air Arms Diablo - However I`ve ended up defaulting to the H&N FTTs as they come a very close second and I`ve got heaps of them stored in the cabinet

    --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    Chapter 7

    Customising:

    Was it worth it? Well.."It was for me" Mainly because I now have a true PCP Carbine coming in at just a tad under 38" (a full 41/2" shorter than the OE rifle) - I love the new found point ability that this now gives me in the field.

    The 17" LW barrel gives me back the original `Turbulence Void` in front of the Air Stripper too and even though it is now admittedly a little bit louder than the original (by about 6 decibels) it now seems to group virtually any decent quality pellet that I feed into it - Air Arms Diablo seem to go best though.

    The best thing I like about my own M.rod now is it`s individuality - I not only love the fact that it`s now a `one off``air-rifle but I really like that it`s got a true multi-cultural background - a mixture of input and Airgun talent from across the world.

    An American platform - A Unique Australian Hardwood Stock - A British Trigger AND Magazine System (Theoben made those originally) and now a truly competition grade German barrel - Of course I should also mention the British scope mounts (Sportsmatch) Japanese Scope (now a Nikon 3-9x40 AO) and the very good `Harris copy` Chinese Bipod too.

    The other good thing is that because of the original reasonable price of the M.rod it enabled me to do all the fun things to it that I have done - After all I never would ripped into to something as classy and expensive as an AirArms or a Daystate.

    Finally here is the finished article


    "For it is the doom of men that they forget"

  • #2
    This post has been copied from another thread Forum.

    As many of you know, the benjamin Marauder is one of the few truly "Tunable PCP's"
    There are a few differing methods published/posted all over the net but as one of the first Marauder owners in this country I thought I should share what I/we have learned over the past 18 months (that includes the colletive knowledge of Druid & a few others + a thanks to Oleg for bringing them in)

    My tune has worked well in a few rifles if your looking for max, effective power with a reasonable shot count, basically a hunting type tune.
    With an OEM spring & using Crosman Premiers it should give a consistant 30 shots at 930 - 940fps & was very accurate in mine. (.22 cal = 28ftlb)

    Spring tension - 5 turns in
    Hammer travel - 1 turn in
    Vel, screw - 2 3/4 turns out

    These settings also work well as a starting point in a .25 cal but with a shot string of 16 shots.
    In either cal, this tuning method below will have the same effect.

    The idea is to get the Hammer/Valve combo working so that it is in "partial lock" for the first few shots.
    This is where all rifles differ & it depends on your fill pressure & how low you intend to shoot the pressure down to.
    Assuming 3000psi fill. you don't want the hammer hitting the valve hard enough to fully open it on those first few shots. You want the 3000psi to be working against the valve to resist the hammer blow until the pressure drops to just above the mid way pressure in your shot string.
    That way you get a nice shallow rainbow curve in your velocities across the full length of the shot string & the first & last shots are about the same speed with the middle ones only a few (up to 10 or 15) fps faster.

    For me, I use a 30 shot string & my valve doesn't start to fully open (the highest fps in the middle of the string) until I get down to around 27-2800psi but I only shoot down to 2200 (to keep my velocities up & save some pumping

    Someone like Druid who shoots down to 1800psi with a much longer string at lower velocities would have set his valve up so it was in partial lock until it got down to about 2500psi.

    The way to do it is to open the velocity screw all the way to 4 turns out.
    Now charge the rifle to just above your chosen mid point (24-2500 for a long, slow string or 27-2800 for a shorter faster string) & only fire about 3 - 5 shots over the chrony at a time before topping up to that pressure again, (It will chew heaps of air with that screw open & you need to keep it in that pressure range where you want the valve to fully open)
    Adjust the Hammer Travel & spring tension until you get the highest velocity you can at that chosen pressure.
    Now you must work your way up, not down so start with the hammer spring & travel backed off completely. (note that this means screwing the travel screw inward to shorten the stroke)
    The reason being is that you are trying to find the point where the hammer begins to overcome the pressure acting against the valve so it can fully open it.
    If you started out with the hammer hitting the valve with full force, you will only see the velocities drop off because you have started with the hammer fully opening the valve right from word go.
    For a similar reason, if you do this hammer/valve tune at too high a pressure (say 2900psi) you will have a shot string that will be in continual decline from very early in the string. Or alternatively it will give you a string that can go "screaming Eagle" for about 10 shots & then fall off it's perch />

    Once you get that valve opening fully at that mid way pressure, then close down the velocity screw to increase your shot count & set it at your desired velocity. (Low 900's or less is best for accuracy) & you should get a nice flat curve & a long, consistant string after re-filling to max charge pressure (3000psi)

    Above is basically the "A Team" tuning method with a few bits added to help people understand the do's & don'ts as well as the "why for's"

    The A Team were/are a bunch of Guys who helped Crosman develope the Marauder from the drawing board to production & then onto National & International Competition.

    I suggest you familiarise youself with thier Tuning Guide too.


    Also check out Druid's long standing Marauder Workshop thread for a wealth of information as we worked our way through the early stages of getting to know these Practicle, affordable & very Capable Air rifles.

    I wish you many hrs of enjoyment with your new toy & hope that this guide will help get you on your way to bringing the best from your "Benji"

    Cheers, Mick.
    Attached Files

    Comment


    • #3
      Wahey - Another great mod for the rod

      http://www.network54.com/Forum/79574/thread/1383247236/BENJAMIN+MARAUDER+PRESSURE+REGULATORS+NOW+AVAILABL E+AGAIN.

      I never really fancied one of the earlier models as I wasn`t prepared to lose the pressure gauge - Always thought that was a bit too much like not having a fuel gauge on a car
      "For it is the doom of men that they forget"

      Comment


      • #4
        Druid,
        I am a normal sized person. I have handled a Benjamin Marauder and it seemed a bit on the hefty side for me. I would dearly love to source an Air Arms S200 sport but they don't seem to be available in Australia so maybe a modified Marauder is doable. I note that you said it points better with your mods (which I really like by the way). How much does yours weigh with the scope mounted

        Comment


        • Guest's Avatar
          Guest commented
          Editing a comment
          Originally posted by Waldo" post=38343
          Druid,
          I am a normal sized person. I have handled a Benjamin Marauder and it seemed a bit on the hefty side for me. I would dearly love to source an Air Arms S200 sport but they don't seem to be available in Australia so maybe a modified Marauder is doable. I note that you said it points better with your mods (which I really like by the way). How much does yours weigh with the scope mounted
          Waldo,

          If you like the Marauder but it's too heavy, you might look at importing a Discovery. Smaller in the hand, lighter, PCP, is basically the Marauders Little brother.

          It's only single shot though, however I did read on another forum that someone was trying to engineer something in regards to a clip - don't count on it though.

          Talk to Jeff at Hi-powered Airguns.

          Luke


          MOD EDIT Post relocation

          So I've been looking around at ways I can get the gun shooting alot better. Came across this Mod from Bstaley, and it seems pretty easy to do (I think).

          Anyway, just wanted some feedback on what you guys think. Druid and Matt, and anyone else with Mrods PLEASE chime in.

          Luke

          http://www.network54.com/Forum/79537/thread/1315440196/Poor+man%27s+M-Rod%2C+P-rod%2C+etc-+%26quot%3BRegulator%26quot%3B+explained+%28Long%2 9

      • #5
        Well Waldo according to my highly questionable $10 fishing scales - It all weighs in at 4 Kilos smack-on
        "For it is the doom of men that they forget"

        Comment


        • Waldo
          Waldo commented
          Editing a comment
          Thanks Druid. Maybe a modified Marauder is the go for me.

      • #6
        I thought this was a good video on How to replace the Benjamin-Marauder Hammer-Spring

        http://shootingaustralia.net/forum/air-rifles/224-benjamin-marauder-workshop

        Too easy
        "For it is the doom of men that they forget"

        Comment


        • Guest's Avatar
          Guest commented
          Editing a comment
          Originally posted by Druid66" post=65456
          I thought this was a good video on How to replace the Benjamin-Marauder Hammer-Spring

          http://shootingaustralia.net/forum/air-rifles/224-benjamin-marauder-workshop

          Too easy
          No video there Druid.

      • #7
        Try again

        http://www.youtube.com/watch?v=uhtPan7RCU4
        "For it is the doom of men that they forget"

        Comment


        • #8
          Thought I'd post this here. The claims are amazing, and I'm certainly going to look into it as the performance of my mrod in comparison is poo.
          Enjoy fellas!

          http://www.marauderairrifle.com/forum/viewtopic.php?f=28&t=7698

          Comment


          • #9
            After the huge success I had from fitting an Altaros Regulator to my Webley Raider I decided to buy another one for my m.rod - Listed below are the before-and-after figures I got from fitting the aforementioned device.

            Notes:

            Rifle tune on both tests: Air Screw = 2.25 Turns OUT - Hammer Tension = 2.25 Turns IN - Hammer Stroke = 2.25 Turns IN

            The above rifle has a 17" Lothar Walther barrel which decreases the standard OEM power output by approx 10%

            Pellets used on test - H&N Field-Target-Trophy .22 / 14.66 Grns

            Fill pressure on both tests = 3000Psi

            Pre-regulator test results:
            Fps
            800
            792
            795
            800
            798
            803
            793
            801
            803
            805 - (2750PSi)

            808
            801
            805
            804
            806
            808
            811
            803
            800
            802 - (2500Psi)

            804
            806
            802
            798
            796
            792
            795
            796
            790
            784 - (2250Psi)

            790
            787
            790
            775
            775
            772
            777
            772
            773
            769 (2000PSi)

            End Test - 40 x Usable Shots @ approx 21 FPE


            Results with same tune - Altaros regulator installed and reg set at 1900 Psi

            Start Pressure 3000Psi
            Fps
            720
            724
            730
            728
            730
            729
            730
            727
            725
            720

            732
            728
            733
            730
            725
            724
            726
            724
            723
            720

            726
            721
            728
            730
            724
            726
            727
            727
            724
            726

            728
            723
            715
            720
            703 - (Off Reg)

            End Test - 35 Usable shots @ 17 FPE .......Go figure?!
            "For it is the doom of men that they forget"

            Comment


            • Guest's Avatar
              Guest commented
              Editing a comment
              Interesting. Did you fully open your Port?
              heh - that sounds kinda strange.

          • #10
            I thought your pre-regulator tune looked to be working alright, why fix something that ain't broke?

            Comment


            • #11
              The whole point of this test was to compare the rifle with and without a reg plus no other alterations made.

              I have however tried these settings since V=3 - T=3 - S=0 with the intent of pushing up the power-output and this merely pushed the pellet speed up to an average of 785 Fps and the Usable-Shot-Count down to around 30

              Then with this higher state of tune increasing the reg pressure slightly to 2000 Psi increases the speed to the low 800s but then it falls off the reg at only 25 shots

              Needless to say the reg has now been removed - The 22-22-22 Druid-Tune has been re-instated and now I look forward to Oleg telling me "I told you so Mark"

              It`s not all bad news though at least my m.rods now back where I had it and the other regulator on my 12FPE Webley Raider is still working brilliantly
              "For it is the doom of men that they forget"

              Comment


              • #12
                Well at the least now you know, nothing ventured, nothing gained, will be watching for Oleg's comments :P

                Comment


                • #13
                  Me too - It does`nt make a lot of sense does it?! - After all the reg does`nt take up that much space in the air-cylinder and slower velocities AND lower shot counts are`nt something you`d ever expect when you `up-grade` are they!? :lol:
                  "For it is the doom of men that they forget"

                  Comment


                  • Guest's Avatar
                    Guest commented
                    Editing a comment
                    Mark, now that you've figured out that a regulator is an add-on that can make things more complex let's try to work out what is causing it to glitch.

                    First, can you tell me if your regulator has a way of adjusting the volume of a regulator chamber?

                    Second, I'd say that 131 Bar is a bit too high for a regulated gun and you are using too much air per shot. I'd bring the regulated pressure down to 100 - 105 Bar.

                    Third I'd give the hammer spring maximum pretension and set the hammer travel to 14 turns and set the transfer port to fully opened. From there you would need to record a shot string of roughly 40 shots, just to make sure that your velocities are consistent.

                    According to my calcs, Marauder hammer is way overweight and causes air waste, but there are people on yellow forum that insist that it is possible to tune regulated Marauder even without trimming the hammer. I recon you have a chance here to prove me wrong.

                    So what you would need to do is start shooting through the chrony, while backing out the hammer striker by 1/4 turn with each shot. In theory, your velocity should start rising up to a certain point and then will be on decline. Once you've located that point, try recharging and getting the full string reading. I would expect you to get around 40-50 shot at 25-28 ft-lbs, depending on how lucky you are in striking at the optimal tune.

                    This method is extremely crude, but may give you a starting point.

                    Regards

                    Oleg

                • #14
                  Nice one Oleg

                  I reckon you`re right it`s gotta be Air-Wastage - and that can only be linked to Hammer-Strike-Adjustment - Winding the reg right down to it`s minimum would indeed be a good first step - Always a bit of a stab in the dark as the Altaros regs are`nt that well marked This time I shall tread more carefully :P The main thing of course is that I don`t manage to lock it down completely shut like I did on the Raider and then have another `pipe-bomb` to defuse :S

                  Hey I`m beginning to think that a lot of this regulator-malarkey is very much dependent on what power-output you want and what air-capacity the rifle actually has.
                  For example: a slim-cylinder carbine will benefit enormously from a reg if you`re just aiming to get a much higher shot-count at 12-FPE power-levels - However if you`re after FAC type power-levels and would be happy with a similar usable-shot-count with a flatter and more consistent velocity-curve a Hi-Cap Buddy-Bottle Rig is the way to go.

                  On-wards - More Chronying - More experimenting - YES!
                  "For it is the doom of men that they forget"

                  Comment


                  • #15
                    Druid,
                    did you take a look at the link I posted earlier? I think that if you went down that road, you'd get alot better results than what anyone on here can advise you of.

                    Proof is kinda in the pudding. Take advice from guys that have done the mods and got the results rather than those that speculate.

                    Comment

                    Working...
                    X