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FAS 6004; rediculously low velocity

4783 Views 15 Replies 9 Participants Last post by  1911
Last January I bought a FAS 6004. The fit and finish of the pistol is superb, everything is there to make it a very usable 10-meter competition fun gun.

The only problem is the velocity is only 303-320 fps with best 7.0 gr. match pellets. I tried 3 different Match pellets, but it didn't matter;still very low velocity!

I contacted AoA and asked them why they advertised 400 fps. when there gun only puts out 300 fps. They stated to me that was the info supplied by the manufacturer; Chiappa Firearms. The big problem is I don't have any targets the thickness of toilet tissue and because the velocity is so low, over half of the pellets won't penetrate the clay in my silent pellet trap.

I haven't been in contact with AoA in a while, so I may contact them on Monday and see if there is a "fix" yet for there wondertoy........................
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How's the accuracy Ray? If it's consistant and accurate I wouldn't worry about terminal velocity. At least not for a 10 meter air pistol.

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The accuracy is very good. The main problem is the pellets won't penetrate the clay on my silent pellet trap and over half of them bounce off the clay after they penetrate the paper. If there they had been a little more honest in their advertising and stated correctly that the velocity was 305-320 range I would not have bought the pistol.

I have an IZH46 and a 46m. The low end 46 still does 395-405 fps and easily stays in the clay of my silent pellet trap. Does anyone know of a fix to get the velocity close to 400 as advertised?......................
The manual doesn't say anything about oil in the air inlet but you might try a drop of silicon/pellgun oil. https://www.chiappafirearms.com/uploadimmagini/altrimanuali_documento_7.pdf

If it's punching nice groups I'd just cut a piece of 1" styrofoam and put it in front of the clay to catch the spent pellets. Obviously it bothers you but the object is tight groups not terminal velocity. Speed is moot as long as it's consistent shot to shot.

I have the same air pistol that I also got from AofA, they did not seem to be willing to do anything about the velocity but here is a link to tuning the air pistol the gets you a very good increase of velocity.


By tightening the seal between the barrel and the air chamber you gain quite a bit of velocity. Even with the tune up the velocity is still very low but the tuneup is worth doing.
Thanks so much! I will be doing the tune. You know; sometimes I really get sick and tired of having to deal with the liars and BS artists that are so full 0f themselves that they see no need to be honest and actually practice any semblance of integrity..........
Hope the tune-up helps. The tune up shows using a metal shim washer, I got some of those and the inside diameter was just a bit tight and instead of trying to ream out the shim washer I just cut one side of the washer so it sprung open just a bit and then fit it in. Let us know how it works for you. I was a little disappointed that Airguns of AZ did not know about this tuneup. Good luck with yours.
fas 6004

I bought one too, now it's going back to AOA for a refund
it's the second gun I've tried and both had the same problem
nice concept, POS
I did the tune up and mine works great now. The tune up is fairly easy to do. The breach seal shim and barrel adjustment made a big difference in mine.
I did the tune up and mine works great now. The tune up is fairly easy to do. The breach seal shim and barrel adjustment made a big difference in mine.
Do you know by how much your velocity was boosted? And if it's consistent?

I've been considering buying one of these for awhile, but may hold off now. Dunno.
It's been a little while ago but I do remember it came up to the advertised fps. by my crony with RWS Hobbys. It has continued to shoot around the same fts after about 700 shots. It is a real tack driver and a pleasure to shoot after the mods. When I first got it it was shooting about 50fps. low with the RWS Hobbys. I would buy one again but only if I did the mods too. I'm a lefty and I love the ambi grips. Not as accurate as my HW45 but a great shooter for the price imo.

The gun is a POS send it to me and I will send you a $100 to help cover your misfortune.....PM me if interested...
LOL, it's is a very nice gun although I think maybe overpriced. I actually prefer my Daisy 777 and 747 to it. Trigger is little better than the Daisys but not a lot. The Daisys are just as accurate and easier to maintain IMO.
How's the accuracy Ray? If it's consistant and accurate I wouldn't worry about terminal velocity. At least not for a 10 meter air pistol.

Frank I have the same problem with mine the trouble with this pistol is that when Chiappa took over the production
of the excellent 604 they screwed up the barrel and the air discharge port, mine has the exact problems RAY 1946
commented on. The 604 was superb, Chiappa cut corners the breech seal does not fit the air discharge hole there is a gap between them that is difficult to fit due to insufficient depth of the barrel O ring here is a treatise on the repair, takes a lathe and a McMaster xring to fix."

"The problem with the FAS is its barrel. Its breech is not correctly finished and needs popping on a lathe to touch the inner recess or following the method on here...Its an easy job for an engineer but could be daunting for someone without hand skills.
It also wants a phosphor bronze brush shoving through to knock off a couple of high spot burrs inside ...You need to use a 10x glass to see them but they are present....Alternatively use the method on here, using wet and dry paper.
Next the breech seal of the FAS sits in a groove which is a shade too deep. It needs a backing washer or a twirl of floss to the rear of the O ring to lift it up to prevent gas loss and prevent lower edge of the barrel nicking the bulkhead face below the transfer port..Which can occur when this shallow seal beds in.The SIG groove is 0.3mm less shallow being just enough to not give rise to the same problem..
Once sorted the FAS velocity rises 30 fps and seals nicely without the metal of the barrel contacting the bulkhead face.
I use an O ring in place of the hard alloy barrel fixing washer ...it has a touch of give but keeps the barrel nudged up until the screws are tightened ...most throw out this alloy washer as in Stoffs post on here..but locking up the barrel can then be more of a guesstimate. With a prouder positioned seal, i still feel the positioning washer has its place!
Finally a piston pack of 0.3mm will give both guns a 30 fps shunt upto 400 fps territory if you want that."

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On mine, I removed the piston, and applied two layers of aluminum duct tape to the piston top, then trimmed carefully with a new razor blade. Reassembled and got a nice velocity boost. It was around 400 fps with Hobbys. Redoing the barrel/chamber interface is a must also. These two mods make the gun much better and aren't difficult at all.
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