Gamo’s GX40 magazine-fed carbine PCP is made in the UK, and as far as I can tell, apart from the stock, is exactly the same as certain BSA models. Gamo (Spain) bought BSA during the 1980s, and air rifles are still produced in Birmingham, England – a possible explanation for the similarities.
The GX40 we received for testing is in .177 calibre and came standard fitted with a muzzle-brake, and although this kept the rifle short and handy (basically a carbine), it proved to be rather loud, so I fitted an aftermarket suppressor (½UNF thread).
Two features stand out on this rifle: the large and comfortable black synthetic stock with a pistol grip, and the 10-shot magazine. The butt-pad is of sturdy, high quality black rubber. Overall length, with the muzzle-brake fitted, is 101cm and it weighs 3.8kg.
The rifle’s air cylinder is rated for a maximum pressure of 232Bar, which is considerably more than that of my Air Arms 400 (less than 200Bar), and having only a dive cylinder with a maximum pressure of 200Bar, I could not fully top up the cylinder. The gauge is mounted in front of the cylinder, beneath the barrel, and is easy to read. The fill adaptor on the rifle is covered with a piece of plastic that slides on and keeps dust and dirt out. This is the only part of the rifle that looks rather flimsy and out of place.
The action works with a bolt, and to remove the magazine you need to pull the bolt fully back. The 10-shot magazine then slides out to the left. The magazine has a knurled rotor, and to insert a pellet you need to line up the hole in the cylinder with that of the housing, something that can be done with one hand, while handling the pellet with the other. The magazine fits into the receiver one way only, and a magnet pulls it into position once it is partially inserted.
To shoot, you close the bolt, which feeds a round from the magazine, disengage the safety and fire.
The magazine cylinder rotates automatically when the bolt is opened, indexing another pellet in line with the chamber. It’s also numbered and you can see at a glance how many shots are left. A white dot appears on the magazine when the last shot is fired.
With this type of indexing system it is possible to chamber more than one pellet if you’ve forgotten that a pellet was already loaded earlier. This happened to me on a few occasions, but I was able to get rid of both pellets by simply firing the gun.
The plastic two-stage trigger has a rather long first stage and the trigger break is fairly vague compared to that of an Air Arms, but with practice I got used to it and found it surprisingly good, even for shooting tight groups. The trigger is adjustable, but the change in maximum and minimum settings not as distinct as I would have liked.
The safety is a trigger-shaped lever ahead of the trigger; pulling it towards the trigger engages the safety; pushing it forward readies the rifle to shoot. I had to constantly remind myself to engage the safety before chambering another pellet. Engaging the safety after reloading is not a safe practice.
The rifle comes with a fill station adapter and I filled the cylinder to just under 200Bar. I tried JSB Monster pellets (13.43gr) and managed 20 shots with all velocities between 826fps and 811fps, of which eight shots measured between 812 and 813fps. From shot 21 to 24 the velocity dropped to between 809 and 803fps, and from shot 26 velocity dropped below 800fps. I checked the pressure after shot 25 and the gauge read 100Bar. The Monster pellet’s energy at a velocity of 812fps is 20ft-lbs or 27J.
Read the full article in the November 2018 issue of Magnum.