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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
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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.
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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
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
/> 
.......Go figure?!
- 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:
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 
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