It’s been roughly three months since I got my FN303s up and running and I have some notes to share and answers to some questions sent in.
If you bought a surplus FN303 from Keep Shooting or Uncle Sams Retail Outlet it is, in my experience, going to require both a launcher and tank rebuild which I have covered in previous posts. If you want to just give it a try as-is and have a hand pump don’t bother pumping it above 1,500 psi. The launchers only require about 900 psi to operate and that will give you enough to try a few rounds without wasting a lot of effort pumping it up to 3,000 psi. Put a good dose of air gun oil down the air tube before you connect the tank to the launcher just to give yourself a little better chance.
The Taousa hand pump I linked to in an earlier post has the connector included to attach to the FN303 tank. It takes several hundred pumps to get a tank up to 3,000 psi but it can be done. When you initially receive the pump go ahead and use loctite on the screws for the foot pegs and the handle as they will want to fall out very regularly even if you tighten them securely. The instructions with the pump aren’t a particularly good translation but I have found it helpful to add a few drops of air gun oil into the intake hole located under the handle every time you fill a tank to help keep the thing well lubed.
On the subject of lubrication it really is necessary to drop ~4 drops of oil down the air hose of the launcher every couple mags. I have an FN303 that I keep in my shop and use quite a bit to snipe the squirrels on my property. It started leaking slightly after about 4-5 mags without lube and I was a bit concerned that the seals were blown out. It turned out that it just needed some oil. At this point it has had maybe 300 rounds through it and is still going strong. I turn off the air tank valve when I’m not using it but when kept well lubricated the seals in the launcher will still hold enough pressure to launch a round with force.
The RAP4 rounds make an excellent squirrel hunting round provided you select rounds for a concentric tail section to ensure accuracy. The FN rounds are more accurate and work better but they are so much more expensive it just doesn’t make sense. The First Strike paintball rounds are marginal for squirrels. The plus side of the RAP4 rounds is that they seem to be usable for dozens of firings provided you get around to recovering them.
There seems to be a lot of confusion about the requirements for hydrostatic testing of the FN303 tanks and I don’t have a good answer on it. What I can tell you is that if you take one (or a dozen) to your local dive shop they will likely fill it up for a few bucks whatever the date on the tank may be. What will help getting your local shop to fill them up a second time is if the thing doesn’t leak like a sieve. After rebuilding all my tanks once and finding that several still have leaks I recommend paying particular attention the the o-ring on the tank neck to ensure that it doesn’t get pinched when putting it all back together. Of the dozen or so tanks I rebuilt maybe half of them leaked out the neck as I had inadvertently pinched the seal when reassembling. With careful reassembly of those and the addition of teflon tape it looks like I have them all sealed up more or less airtight.
If your FN303 is anything like my surplus ones are the sights are probably rusty and look like shit. Although the iron sights are crap they look a lot better if you clean it up a bit. Remove the front and rear sights and dunk them in Evapo Rust for a few days to clean them up. Some of mine were heavily rusted/pitted and required multiple dunkings but once they are cleaned up it helps the whole launcher look a lot better.