Reset barrel in FAS 604

[kiyoti]

I received a FAS 604 that was completely disassembled from my brother's estate. I found a guide online by Frenando Perello and bought a seal kit from the UK and was able to rebuild it. However, the barrel was removed from the slide and I have not found any info on how to properly set it for proper mating to the valve body when closed.

Thanks for any help or advice you can give,
Steve

[slofyr]

... how to properly set it for proper mating to the valve body when closed....

The goal is to prevent the barrel from contacting and marring the port face while adequately compressing the breech seal against the port face. Make a port face shim with two layers of standard 20# printer paper. With the two screws of the barrel clamp snug but not tightly holding the barrel, and breech seal removed, fold the paper shim down over the port face and close the top until it latches. Now, tap the barrel from the muzzle end with a wood dowel and light hammer. Being partially snugged in the clamp it will move back, contact the paper shim and stop. Lift the top and secure the clamp screws. The only structural load on the barrel is from the compressed breech seal, so don't over-tighten the clamp screws because they thread into alloy. Install the breech seal and test fire. With the 604 a two-paper shim should be enough, but if you think the seal is over-compressed reset the barrel with a shim from three pieces of paper. During use, it's worthwhile to occasionally put a finger print of silicone oil on the port face to keep the breech seal happy.


The OEM breech seal in the early 604 was not a standard o-ring. If you have a later production pistol it may have an o-ring which appears to disappear into the groove. In that case, you may need to put a .005" shim under the seal. They are commercially available, or make one from paper.



The above applies to the newer 6004, too, but there are other concerns with that one before reseting the barrel. I'll be posting some info about that pistol soon.

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

[kiyoti]

Slofyr, thank you, that was exactly what I needed. The breech face is already gouged, but it appears to be outside of the o-ring sealing area. The pistol is now working fine. Thank you for assisting me in my entry into 10 meter air pistol.

Steve