When I first started tuning of my Armada, when I shot over the Chronograph with a 3000psi fill. The best I could get was a 713 fps shot. I thought that was pretty pitiful considering how much I had invested in the gun and I knew a $30 Crosman 760 Pumpmaster could get around 650fps with a .177 pellet right out of the box. 
So, the search was on. I soon found that most unregulated Benjamin Armada/Marauder guns were shooting much better. Out of desperation I asked why my gun was shooting like it was in a Facebook group. Within 15 mins a kind person answered “Check your breech o-ring”.

Marauder Breech .25 o-ring aka #10 (fraction - inch - mm) W 1/16 0.0625 1.5875 ID 1/4 0.25 0.00635 OD 1/8 0.125 0.003175

Sure enough, when I pulled the bolt back and peered into the breech I found the o-ring was gone! I must have shot it down the barrel when firing the first or second clip, seems like I remember forcing a pellet or two into the chamber on my first hand pumped fill. Oh well, live and learn eh?

So, I searched around the house and found a cheap set of o-rings that I had bought at a dollar store for something else, found one that looked about the same size, lubed it with some plumbers silicone grease and stuck it in there. BOOM – instant 100fps increase per shot. By the way, I now run a Durometer 70, and keep spares in my shooting kit.

Below are the results:

Average: 700.7 FPS
SD: 10.7 FPS
Min: 668 FPS
Max: 713 FPS
Spread: 45 FPS
Shot/sec: 0.1
True MV: 715 FPS

Average: 804.4 FPS
SD: 5.5 FPS
Min: 794 FPS
Max: 812 FPS
Spread: 18 FPS
True MV: 820 FPS

Breech o-ring specs:
Some auto parts store’s will call it a #10
Hardware store or online:
Fraction – Inch – Metric
Width 1/16 – 0.0625 – 1.5875
Inside Diameter 1/4 – 0.25 – 0.00635
Outside Diameter 1/8 – 0.125 – 0.003175

Tuning the Benjamin Armada/Marauder

The MarauderAirRifle forum is an excellent source for all info regarding the Benjamin Marauder and the Benjamin Armada 25 (The Armada has the same internals as the Gen 2 Marauder – it’s just dress up to look like an AR15 and out of the box accepts all Picatinny mount accessories).

Below are the settings my rifle shipped with and the Hill Tune that I am using now.

Stock tune for my Armada 
Valve Screw(VS) 3.5 (Clockwise all the way in then Counter Clockwise out (CCW)
Hammer Throw(HT) 3.5 (Clockwise all the way in then Counter Clockwise out (CCW)
Hammer Spring(HS) 4 (Clockwise all the way in then Counter Clockwise out (CCW)
Hill Tune as far as I know, I seen these settings in a post talking about the Hill Tune
VS 5.5 CCW
HS 4.5 CCW
If you head on over to the MarauderAirRifle forum – the Abbreviations below will come in handy when trying to understand what they are talking about if you are new to this sport and PCP airguns in general:

Marauder Air Rifle Forum Abbreviations

I want to say thanks to all the guys who share what they have learned while shooting these guns. I am writing this post so hopefully I can help others in the community, then way I have been helped.

On a side note:
Did I mention how accurate and powerful these magnum air rifles are? 24 rounds punched a hole all the way through my not so trusty well shot up and duct taped sand bag.
So when practicing in your back yard it might be a good idea to place a couple shots in each spot on your target and backstop or the neighbors pets or kids might get hurt. Or maybe put a sheet of 1/4 inch plate steel behind your backstop for insurance.
Please share this blog on Facebook and Twitter. If you would like to post some of your tips and tricks you know feel free to send me an email.
Also, check out the links page. If you have any links you would like to see there. Please let me know.
Oh, and check out the APG Store link in the menu. Sure its an Amazon store, but I did take the time to build it, and the cost to the purchaser is the same. Sure if you make a purchase I might make a few pennies, but I have to support this habit somehow.
Thanks for stopping by, Dan Spechtenhauser