
Regular readers of this blog are probably familiar with the Theoben line of air rifles from England, and Theoben’s patented gas ram spring system. The advantages of the gas ram spring are many: Less vibration, no metal fatigue, no spring torque, quieter, and infinite adjustability. Those of us who own Theobens tend to be fanatics about them.
Theoben has pretty much had this technology to themselves since 1982, when they founded the company. One American company that I’m aware of (Vortek, of Farmington Hills, Michigan) tried to come out with their own gas ram spring, but Theoben’s lawyers successfully argued that the Vortek design was a patent violation. Now that Theoben’s US patent has expired, Crosman has come out with their own gas-ram airgun.
In Crosman’s own PR they don’t mention previous art in this field- not surprising, as they’re not looking to promote Theoben!- but they do repeat the same benefits that Theoben has always stressed. They also add one additional one: Their ram is pressurized with nitrogen, rather than with air. This is curious, as Theoben used nitrogen for a time, and then switched to air. Perhaps Theoben didn’t find any advantage in using nitrogen?
The use of nitrogen does suggest that the gas piston is not user serviceable. Earlier Theobens had a user-accessible gas valve, and Theoben distributed a high-pressure air pump used in pressuring the ram. The problem with this was that too many owners tried to pump their guns up to magnum power levels, damaging the ram and destroying the piston seal, and so they went to a factory sealed system that requires sending the ram or gun to a service center if pressure is lost. My Theoben Sirocco is an earlier model with the valve, and I own a pump; this was very useful when I pulled my Sirocco out of the safe a while ago and discovered it had lost all pressure- probably from not having been used in several years.
At a list price of $390, and an advertised price of only $324, compared to $682 for Theoben’s cheapest gas ram gun, I have no doubt that Crosman are going to have a hot seller on their hands. The synthetic stock and camo finishes should make it a fine hunter, too. I am a bit disappointed that Crosman is touting the ability of this gun to achieve 1200fps in .177 with super lightweight pellets (see previous post), but with proper .177 pellets in the 7.5-10gr range, or in .22cal, it should be a fine performer. Doing the math, 1200fps with a 6grain pellet translates into 19 ft/lbs. A 10gr Premier would take that down to 929 fps- ideal velocity for an airgun.
Thanks to Christopher Robinson for tipping me off to the Nitro. You can read his discussion on the Nitro at the Airgun Advice forum.