A look at the Gamo AF10

[Iain K D]

I took the opportunity of having my AF10 apart for a bit of a clean to take some detailed photos of the various parts of the mechanism. There are one or two interesting points about the action, and it’s different in some significant details to the other three overlever single-stroke pneumatics in the Gamo range, the PR15/45/Compact (which have a large degree of commonality between them).

http://i301.photobucket.com/albums/n...%20AF10/01.jpg

First step in dismantling is to remove the two screws that hold the right-hand grip (it’s actually more than just a grip, forming a cover plate for the trigger mechanism as well) in place, located in the centre of the grip and behind the trigger. Some care is necessary here though as these screws don’t go into the frame itself, but into separate steel bushings inserted from the left. The larger of these, in the grip, is quite secure, but attempting to unscrew the smaller screw will just cause the bushing to turn as well and chew up the frame a little (I speak from experience here). It is necessary to grip the head of the bushing with pliers, which is just possible, when removing the screw.

http://i301.photobucket.com/albums/n...%20AF10/02.jpg

With the grip removed the simple trigger mechanism can then be seen. The trigger slides back, guided by a steel pin at its rear end (in the curved slot) and the smaller bushing passing through it at the top. It comes into contact with an arm, pivoted on the valve housing, the lower end of which is visible; the top end of this arm holds the valve closed when the gun is cocked. A spring attached to the frame pulls this arm forward, and must be removed before the air cylinder can be lifted from the frame. There is a spring below the trigger (not visible here) to give the first stage of the pull, and the crossbolt safety catch and how it blocks the trigger can also be seen.

http://i301.photobucket.com/albums/n...%20AF10/03.jpg

This differs from the other Gamo SSPs, which rely on an internal hammer (cocked by the movement of the air cylinder on opening the gun) to knock open the valve. On this gun, the valve is pushed back into the housing, by a step on the inside of the frame, as it rocks downwards on opening the gun (and the air cylinder rocks up slightly).

The two pins at either end of the frame (more precisely, the steel ‘cradle’ forming its top half), passing through the air cylinder and overlever assembly, can now be removed, together with the pin linking the overlever to the tail of the piston rod. This last pin is splined at one end to grip the overlever, so needs tapping out from the other end. The various major assemblies can then be seen, including the magazine which I don’t normally have fitted.

http://i301.photobucket.com/albums/n...%20AF10/04.jpg
http://i301.photobucket.com/albums/n...%20AF10/05.jpg

The arm holding the valve shut can now be seen more clearly, to remove the valve housing the plain steel bushing (which acts as the rear pivot for the air cylinder) is tapped out after which the housing can be gently pulled out.

http://i301.photobucket.com/albums/n...%20AF10/06.jpg
http://i301.photobucket.com/albums/n...%20AF10/07.jpg

The pivot pin for the valve arm is now exposed and can be removed if necessary, the green o-ring seals the join between the air cylinder and valve housing. At the top is my diy breech seal, which fits into the transfer port. One point which puzzles me is the purpose of the white ring behind the seal; if it were felt or foam (and acted as an oil reservoir) that would make sense, but it’s just in a fairly hard plastic (and the manual makes no mention whatsoever of any maintenance requirements).

http://i301.photobucket.com/albums/n...%20AF10/08.jpg
http://i301.photobucket.com/albums/n...%20AF10/09.jpg

Another point which had me puzzled (and worried) at first was on reassembling, with the valve housing in place and pushing the pump in there always seemed to be a leak somewhere. It took a while before I realised that, without the end cap to act as a guide, it was very easy to tilt the piston rod slightly relative to the cylinder, which prevented the piston seal from working. With the end cap in place, even only loosely, it kept everything concentric and allowed the seal to function correctly.

It is necessary to pull the pump/piston out of the air cylinder from the valve end, due to the design of the end cap at the forward end of the cylinder. This is held in place by two short steel pins passing through the air cylinder, which cannot be removed outwards (impossible to grip) but must instead be pushed inwards to clear the walls of the air cylinder. This is only possible with the piston rod removed giving the pins somewhere to go.

http://i301.photobucket.com/albums/n...%20AF10/10.jpg
http://i301.photobucket.com/albums/n...%20AF10/11.jpg

A bracket on the end cap acts as the mounting for the gun’s 10 shot magazine for lead ball ammunition. As soon as the gun is opened slightly, this is pushed upwards in line with the transfer port, which is formed into a chamber. Closing the gun, the magazine is pushed down leaving a shot in line with the barrel. Unfortunately, this doesn’t give any space for a breech seal and so I simply do away with the magazine, load pellets singly directly into the barrel, fit a home-made breech seal ... and get a muzzle velocity more in line with the effort that goes into cocking it.

http://i301.photobucket.com/albums/n...%20AF10/12.jpg
http://i301.photobucket.com/albums/n...%20AF10/13.jpg

The barrel – which is rather lightweight looking – is held in the overlever by a single screw beneath the muzzle. Slackening this allows the barrel to be slid forward slightly (to accommodate the thickness of the breech seal) or removed completely. The barrel also holds in place the two overlever catches which engage with the valve housing, one on either side. One benefit of this design is that the rear of the overlever is completely open, giving very good access to the barrel, making the loss of the magazine no great problem as it is very pleasant to use as a single shot.

http://i301.photobucket.com/albums/n...%20AF10/14.jpg
http://i301.photobucket.com/albums/n...%20AF10/15.jpg

Iain

[mickson]

A first class write up, for me what the pistol section is really about, on a personal note i prefer to shoot the pr15 to the af10 feel & accuracy seemed better to me atb ...mike...

[Iain K D]

Thanks for that.

I've handled, but not used, a PR15 and yes, they do have a different feel. The AF10 is perhaps a bit too light and has, I suspect, a less precise trigger.

Regards,

Iain

[Phil G]

Nice one Iain.

I have one of these and while it needs no attention right now it's good to get an overview.

Many thanks for your effort in compiling this posting.

Good luck, Phil

[Rob M]

Thanks for this! That's an excellent write up, ace photos too! I was interested to read your comments about the breech seal, I tried to improve the seal on mine by reprofiling and polishing the end of the barrel, but reading your account I realised that now I have a lathe, it might be possible to make a small hollow bush out of brass with a recess for an O-ring, this would also reduce lost volume which might help the power a little. The downside would be losing the ability to fire lead balls from the magazine, which although I've got some Gamo lead ball ammo, I've never used.

I've got one of these, while I prefer the Webley Nemesis, these are fun little pistols and quite nice to shoot. Cheers!

[Iain K D]

Some pictures which I hope make clear how I made up my breech seal, from a thick rubber washer.

http://i301.photobucket.com/albums/nn75/IainKD/03.jpg

http://i301.photobucket.com/albums/nn75/IainKD/04.jpg

Regards,

Iain