FAS 6004 Not Firing Pellets

[Tighran]

I picked up an FAS 6004 a while ago to practice and learn with after my Daisy/Avanti 747 was stolen. I had read a few concerns about the quality but it seemed solid and well made so I decided to get it over the Gamo Compact.

I quickly discovered that it was pretty picky about pellets, shooting fine with Crosman Premiers and a tin of "Colt CO2 Pistol Pellets" but not working with RWS Hobby or Meisterkugeln. Occasionally a Crosman Premier will fail to fire the same way the RWS would, with a puff of air I could feel on my hand and opening the gun to find the pellet still sitting in the breech. I'd have to use a tool to push the pellet further into the barrel for it to fire, but this often ended up damaging the pellet and causing it to shoot poorly. I suspected that it was something to do with the skirt size of the pellet, as the "Colt" pellets worked fine in the old Winchester springer I got them with that seemed too tight to readily accept other pellets.

In a perhaps poorly advised move, I decided to remove the barrel to check the breach (which looked fine), and after putting it back in it won't fire the Premiers or Colts either. After seating them a bit further and firing, they would exit the barrel but with a different sound and a clearly different velocity, evidenced by the fact that they didn't punch a hole out of the target but just ripped a hole in it. My suspicion is that the breach face and seals now don't make firm contact against the face with the air port in it and that air is escaping around the seal. There doesn't seem to be much I can do to adjust the barrel position forward and back to tighten this up.
Any suggestion on how I might fix this?

[kevinweiho]

My suspicion is that the breach face and seals now don't make firm contact against the face with the air port in it and that air is escaping around the seal. There doesn't seem to be much I can do to adjust the barrel position forward and back to tighten this up. Any suggestion on how I might fix this?

You can put a shim under the breech to help the o-ring seal more tightly against the face of the air port.

[william]

Is this an exercise in turd-polishing?

[slofyr]

....I decided to remove the barrel to check the breach (which looked fine), and after putting it back in it won't fire the Premiers or Colts either.....

The breech-to-port clearance is probably too wide allowing pressure to blow past the breech seal. Loosen the barrel retaining screws and nudge the barrel back, there should be some slack. With a film of silicone oil on the port face, the breech seal should drag slightly before you hear the latch engage.

[zanemoseley]

I've got a FAS 6004 and it does the same thing. I've had several tins of pellets that it doesn't seem to like. Mine makes a bit of a cork popping noise when this happen. The pistol shoots great but just doesn't like all pellets. I'm curious to see if you find a fix. BTW Airguns of Arizona seemed to be aware of this issue when I contacted them.

[Tighran]

The breech-to-port clearance is probably too wide allowing pressure to blow past the breech seal. Loosen the barrel retaining screws and nudge the barrel back, there should be some slack. With a film of silicone oil on the port face, the breech seal should drag slightly before you hear the latch engage.

This is what I suspected, but since you can't see the amount of clearance when it is closed it is hard to judge, and I was afraid of drifting it too far back and damaging the air port face or breach face.

It came down to trial and error, moving the barrel slightly back if it made the cork-pop sound and failed to fire, and forward if the top failed to close. Eventually I got it back to where it shoots the Crosman Premiers and Colt pellets again without issue, though it still makes the cork-pop followed by a hiss when using the RWS Trainers. I will probably get some silicone oil as well just to help protect the breach seal.

Thanks for the advice; I've now got a picky-but-working gun again instead of an expensive paperweight. Since this seems intrinsic to the design of these lifting-barrel guns I am curious how others like the Beeman P3/P17 and the Gamo Compact get around this issue.

[kevinweiho]

I am curious how others like the Beeman P3/P17 and the Gamo Compact get around this issue.

My Compact has over 10.000 shots and the P17 has about 3.000 shots. I never had any finicky pellet problems.

My Compact is anemic compared to the P17, which is very accurate and hits the steel pellet trap (just as fast as my Izzy) with authority. You can easily tell the overall condition of the seals by just dry firing them; the report should be a sharp crack on discharge instead of a faint pop.

[slofyr]

The breech-to-port clearance is probably too wide allowing pressure to blow past the breech seal. Loosen the barrel retaining screws and nudge the barrel back, there should be some slack. With a film of silicone oil on the port face, the breech seal should drag slightly before you hear the latch engage.

This is what I suspected, but since you can't see the amount of clearance when it is closed it is hard to judge...

With the breech seal removed and the barrel clamp snug [not tight]: stick a shim on the port face, close the top, then tap the barrel back from the muzzle. Lift the top and tighten the clamp. Don't over-tighten because the screws thread into alloy. I haven't measured the factory clearance, but possibly .002" [.051mm] would be a starting point.

I've made this adjustment with the seal in place and without using a shim. The choice is ours. Just be careful not to move the barrel back so far that it rubs the port face.

Cheap shims from an auto parts store are easily cut to size with scissors. Hold it in place with grease. Use wood dowel between the barrel crown and your striking implement.

I have seen a couple of these FAS pistols with rough port faces. Gently smoothing with 600 wet/dry held flat with a small squared block of wood will ensure a positive seal and maximum mv.

As with any airgun, do not store with the breech seal compressed.

[Leon]

Motto of the story is -

If it ain't broke, don't fix it....

[slofyr]

Motto of the story is -

If it ain't broke, don't fix it....

The 604 and 6004 are about as complex as a toaster, and are gems when dialed in.

edit: http://www.targettalk.org/viewtopic.php ... t=fas+6004