Aside from the slight niggle with actually opening and closing the gun, everything had been working fine – until I took it to the club (not having checked it at home first) and straight away felt the cocking stroke to be wrong: on closing the gun, there was some movement, but no real resistance, a slight ‘pffft’ of air, and only then compression. Power was low, I assume, for a couple of shots, but non-existent for a couple of others – the pellet simply did not move.

I’ll say now that I don’t quite know what exactly caused this, but the gun has been stripped, cleaned, re-lubed and put back together – and has worked for another few visits to the club.

I had already found a dismantling guide for the FAS and the 6004 came apart in exactly the same way. One slight constructional difference, I think, is that the 6004 has a brass bushing passing through the valve housing for the rear pivot pin (which on mine, at least, was a tighter fit in this bushing than the frame) The actual finish of the valve housing, though, doesn't really bear comparison to the 604.

http://i301.photobucket.com/albums/n...hiappa/001.jpg

Removing the cylinder and trigger assembly from the frame, it was – still – quite a tight fit in the frame, notice the wear and scratches on the side of the blued steel trigger mechanism housing. I don’t know, of course, how this compares to the original; like the overlever and frame rubbing slightly, does this suggest parts just being cast and then not really tidied up before assembly?

http://i301.photobucket.com/albums/n...hiappa/004.jpg

Of the various parts in the trigger mechanism, the trigger pivot pin is fixed in place, the sear and hammer are not, and the latter was removed quite easily. The hammer had what looked like wear on the bent – full cock ‘notch’, if you will – and its front face below this, where it gets dragged past the sear on cocking (this is visible looking behind the trigger when opening the gun). I didn’t notice what these surfaces looked like brand new: would this really have just been left as the rough unfinished edges of the steel laminations – and still expect to get a decent trigger pull?

http://i301.photobucket.com/albums/n...Chiappa/08.jpg

The trigger mechanism, valve housing and cylinder came apart as expected, after which the piston was removed from the valve end of the compression cylinder. The o-ring here wasn’t damaged at all, so that wasn’t the cause of the fault, but it has gone back in with a light smear of silicon grease – when I first got the gun, I lubricated it with Abbey SM50 through the air inlet hole. The outside diameter of the piston head also got a smear of Moly G-N paste – I suppose with the movement of the cylinder on opening and closing the gun, there could be some contact here.

http://i301.photobucket.com/albums/n...hiappa/006.jpg
http://i301.photobucket.com/albums/n...hiappa/007.jpg
http://i301.photobucket.com/albums/n...hiappa/010.jpg

Examining the bore of the compression cylinder, it did seem to be marked about half way along, possibly just slightly worn. Whether this had some bearing on the issue, I don’t know – could a less than perfectly lubricated o-ring not seal on this portion? This cylinder is supposed to be stainless steel – that is what the handbook refers to, not in the parts list but in the general description of operating the gun: “The stainless steel cylinder is designed to achieve a consistent air pressure with little effort while loading.” I saw what looked like brass edges, beneath an external (and internal – except where it was worn?) plating, mostly at the rear edges where it is chamfered to fit over the valve housing and sealing o-ring.

One benefit of having the gun apart was that the small steel insert at the rear of the frame for the overlever catch to engage with could be removed – access to its securing nut was a bit limited otherwise. This was given an extra chamfer at its top edge, so the overlever catch can ride over it more easily, and the recess in the frame it sits in was gone over lightly with a flat file – just enough to touch some high spots (hmmm - what did I say about the frame being cast and not cleaned up).

http://i301.photobucket.com/albums/n...hiappa/011.jpg
http://i301.photobucket.com/albums/n...Chiappa/12.jpg

The gun now opens cleanly when the release catch is pressed, and can be pushed shut without having to press the catch while doing so. Since the rearsight hasn’t broken yet either, I do still enjoy shooting this – comparisons with the Gamo Compact are inevitable (I’ve had the club gun out) and while that gun is superior in some ways, the handling of the 6004 is undoubtedly much better.

Postscript – this is what individual pellet holes look like at 10 metres on ‘Bisley’ target cards. This was with RWS Geco, which felt slightly tight when loading but still gave muzzle velocities of around 360 – 370 ft/s. I also used up a tin of Bisley Practice which loaded much more easily, but they were a little heavier and slower.

http://i301.photobucket.com/albums/n...Chiappa/14.jpg
http://i301.photobucket.com/albums/n...Chiappa/15.jpg

Iain