FWB 601 air pressure -release issue

[peterleduc]

I just purchased a nice condition 601 and after shooting it 30-40 shots the noise changed. Of course it probably useless to describe a noise on the internet but its no longer a pronounced pop/crack. What is probably more informative is that when I cock it again it has a small pressure release similar to a fart.

Can someone give me an idea of possible problems and or solutions?

Peter

[kevinweiho]

Don't have any FWB ssp air rifles, but when the seals on my 103 was going bad, there was a faint "pop". When you cock your rifle and there is still the typical resistance on the closing stroke, then the piston seal is probably still good. Other problems could be deteriorated seals, debris, old grease/oil or rust on the air valve.

[mmajora]

It is most likely your airgun doesn't release all the compressed air. Check out the travel of firing pin, if it's unobstructed. It is also possible that firing ping doesn't cock properly because of too light sear engagement setting - when you cock, it travel back as it should, but after loading it decocks onto safety. Then, when you pull the trigger, firing ping has shorter way to go and thus beats somewhat weaken. Shot is weaker because it has to be in this case, and there's some air left in cylinder.
Another possibility is weak compression spring - and this occurs either when it's broken, or firing ping spring screw is loose and turns by itself.

[Rover]

There is likely a velocity adjustment screw on the back of the action. Tighten it clockwise 1/2 to 1 turn. It sounds like all the air is not being released. I've seen it happen on a couple of Pardini K58s.

[JSBmatch]

FWB 600 series when they get old are well known for valve seal malfunction and its usually because they have perished mainly due to age and some ingress of lubricant. I have changed many seals on the 600 over the years. They are fairly easy to replace as long as you take note of which way round the cone washer is fitted and you use quality tight fitting metric hex drive keys as the action screws are pretty darn tight.

[45ACP223]

Agree, it's the seal with the brass bushing insert behind the block with the four screws. It's a $4 part and takes about 10 mins. to replace. Typically, you notice that the sound of your rifle firing changes and eventually gets to the point that the pellet won't impact the target at 10M. There is still some air in the chamber that isn't expelled until you pull the charging handle again. Here is a photo that shows the parts. Just put them back together in the right order. Good luck!

[mmajora]

What is probably more informative is that when I cock it again it has a small pressure release similar to a fart.

Can someone give me an idea of possible problems and or solutions?

Peter

Quick and simply test: cock the rifle and let it be for like minute. Shooting sound shouldn't be much more quiet. If it is, seal may require replace.
From what original poster wrote, it's no problem with air, but with air release. Anyway, resealing may be good idea anyway.

Another problem could be dirt on seal or part 1750.212.1 - may cause problem with smooth valve open/close.

45ACP223, what is this three pieces oring-look-a-like?

[JSBmatch]

When I visited the FWB factory many years ago when the first 600 series was being produced, they told me that when working on the valve, extreme cleanliness must be observed with all components, They must be absolutely spotless, no dirt or hairs, do not use cleaning cloths that might leave fibres on the seal. better to rinse clean with a alcohol and blow dry with an air can then assemble with clean hands/fingers.

[45ACP223]

In the photo I posted (came from somewhere on the internet), the o-ring in 3 pcs. must have broken when they removed it. An o-ring is suppose to be a complete ring. Also note in the picture that the valve is positioned backwards in the photo. The long end goes toward the firing pin. Here is a link to a replacement tutorial that zanemosley recently posted.

[url]http://www.targettalk.org/viewtopic.php?f=3&t=49913/url]