I have been fortunate enough to have my hands on an RWS 350 for about a week now and have shot it a bit so I thought I'd give my impressions of this gun.
General
The 350 is 48 inches long and weighs 8.2lbs. I didn't find it near as unwieldy as I have other RWS guns and the weight and length balanced out nicely. Certainly, its one of the lighter of the ultra magnum class airguns. It is generally spoken in the same sentence with the Gamo 1250 and the Webley Patriot/Beeman Kodiak. While lighter and with less cocking effort than the other mentioned guns the others are at or near 10bls unscoped), it also is a tad less powerful. Still, at 21-23fpe in .22, its a beast of a springer. I was getting just over 800fps with 14.3gr Premiers.
Fit and finish
The 350 is typical of RWS guns, meaning the fit and finish is on par with other quality European guns. The wood stock of the gun I am borrowing has a nice grain pattern with checkering. Bluing is dark and consistent throughout. The trigger is nice with an estimated trigger pull of around 2 1/4 lbs. The trigger is the RWS T-05 trigger. The trigger blade is plastic and while that tends to bother some, I've never heard of one breaking or giving any trouble.
Cocking and firing behavior
The gun I am borrowing is barely broken in and as such, there is still a small amount of 'goose honking' when cocking it which I have heard is typical of an oversized seal. I feel certain that with time, this minor noise will go away, and could go away faster with some Macarri clear tar. Upon locking the barrel in place, there was some barely noticeable metal to metal contact; that will go away in time as well. Perhaps a touch of Moly paste would help as well. The cocking arm had a small amount of play in it, less than my TX200 so it wasn't much. The lockup on the barrel was tight with no wobble at all. Firing behavior was the smoothest I've seen in an ultra magnum springer. Recoil was very linear and I was able to remain on target after firing to see the pellet punch holes in paper. Despite being a light weight magnum springer, the recoil wasn't near as bad as my Tomahawk .25, for example. It almost felt like a 14-16fpe springer rather than a 21-23fpe springer.
Accuracy
I had planned on testing several pellets out of the 350, and I still might, but my first pellet choice seemed to be one the 350 really likes. 14.3gr Crosman Premiers were giving me nice ragged hole groups at 20 yards and easy nickel sized groups at 30 yards. All groups were 6 shot groups. All were fired from a sandbag with a very loose hold to allow natural recoil. I used an B-Square adjustable mount and a Leapers 3x9x40 TS scope. The mount has held well despite me choosing not to use the recoil stop pin. Since this is not my gun, I didn't use the stop pin for fear of scratching the receiver. I tightened down the mount and I checked for creep after every 3 shots. So far, about 50-60 shots later, the mount has not moved... a true testament to the balance of weight and recoil of this gun.
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I've still not done any serious testing at longer ranges, but plinking at a large poplar leaf in a tree at a distance of 55 yards showed groups that appeared to be around the 1.5 inch mark. Offhand, I can consistently hit a 3 inch spinner target at 20 yards and hit the one inch spinner about 3 out of 5 shots. This is in no way a representation of the gun itself, as my offhand shooting with most any of my guns gives me the same results.
Conclusion
I like the 350. While not as powerful as the other ultra magnums, I'm sure the extra 3-5fpe they offer wont kill a squirrel any deader. It's accurate and with less practice than many other springers, is a nice bench gun. The light weight makes it an ideal field gun and the light cocking effort makes it a great high powered plinker.
Many thanks to Ledlauncher for the opportunity to test out this fine gun.