A New Air Pump and more tales of the Air Arms Shamal

Two weeks since my last post, well Chrimbo is a busy time. With the arrival of a 9 week old Bedlington Terrier/Whippet lurcher pup things got a trifle hectic. We call him 'Scatterbone' and things are still hectic, but soon we'll have him out in the fields coursing bunnies for the pot.

I've been topping up the Shamal with air at the local gun shop for 3 quid a fill and could see that as being expensive with the amount of shooting i'd like to be doing , so today we popped to Gloucester to get Scatterbone his jabs and then went into Allsports and bought a Hills Air Pump. There's a bit of concern about moisture getting into the air reservior  with hand pumps compared to the dry air you get from a bottle and you can buy Dry Pacs to fit onto the pump to absorb any moisture, but the bloke at Allsports reckoned in all their time handling PCP's they have never seen any problems with moisture, and though they could have sold me a Dry Pac for an extra £40 on top of the £139 I paid for the pump, they said it wasn't really worth it, and they've been dealing in all kinds of guns for over 60 years.

The pump came in a box with very simple instructions on the back; simply bolt on the footplate with a supplied allen key, screw on the handle, and screw on the hose at the base (I used a 14mm spanner to secure), then you're ready to go. The Shamal doesn't need an adapter so the hose screws directly onto the fill valve(same 14mm spanner tightens this), well this one doesn't as its quite an early one (00071) and Air Arms 1st venture into PCP.

This is a 3 stage pump which means that it's 3 pumps  built inside each other working on both the up stroke and the down stroke. It's very easy to pump until the pressure in the reservior is the same as the hose. Then you're filling up the rifle and you have to put a little more effort into each stroke which increases as the pressure builds. Pressure can go all the way upto 275 bar (4500psi), though I found 185 bar was ideal for the Shamal although its written on the side of the rifle that 207 bar, 3000psi was the maximum fill level. I found that if I stopped for half a second at the end of each stroke it filled quicker, which I could easily see on the guage at the base of the pump. Being 6 foot tall it was a lot easier to bend my knees slightly and put my body weight behind the down stroke with a straight back, for me it was really little effort to fill the rifle though i reckon i might be a little knackered filling to 250 bar. At the base of the pump is a small brass knob which you tighten up before you start pumping; this will release all the air from the hose when you loosen it after filling the air reservior. You end up damaging seals and all sorts if you disconnect with 200 bar of air pressure in the hose.

All in all a good investment as i've filled the Shamal up twice already this afternoon already saving me 6 quid at the local gun shop - admittedly I could have shot longer on the first fill but the pellet speed would have started to drop off. This way I can just keep the Shamal firing 50 or so good shots at the top off the power curve, and not need to adjust or compensate on the scope other than for distance and wind. The scope will be zeroed  at 30 yards, spot on for those 50 shots.

  

On any PCP, the trigger releases a weight known as a hammer, held back against a spring - this springs fowards and strikes the stem of a hammer valve which releases some of the air in the reservior into the barrel, which expands rapidly, sending the pellet flying out the barrel. If I filled the Shamal to it's max pressure of 209 bar, a .177 pellet would exit the muzzle at 700fps. As the the pressure drops in the reservior, the pellet's speed increases creating an upward curve, until we get to 185 bar and a pellet speed of 800fps. I then get 50 shots at this speed until the pressure drops to around 100 bar, where the pellet speed will start to drop off. Back down to 700 fps over the next 20 bar used, at which point the pellet speed will start to drop more drastically, creating the downward curve, creating your power curve. If firing at the same paper target, the 1st shot would fall 3 inches low of the point of aim or bullseye, with the next 20 shots creeping up to the POI, the next 50 shots hitting the POI, the next 20 shots dropping slowly down to 4 inches below the POI, and after that dropping off more drastically.

 That is why I like to fill the Shamal to about 185 bar and top her up again after roughly 50 shots, this pretty much garauntees my POI through my scope. So for me the hand pump is ideal, supplying free air after an initial investment, and my hieght and wieght make it easy to use. If i'm out hunting I wouldn't really need more than 50 shots anyway, and if I did it's not really that heavy to carry to a hide, though if I were stalking I could see it getting a bit cumbersome.

In a later post I will do a full write up on the Shamal and let you know how well it performs.  TTFN.

Wing Commander Sir Nigel Tetlington-Smythe.