The best ammo for YOUR Viper is the ammo that delivers the best accuracy in YOUR rifle.
Sorry, but that's the way it is with spring piston air rifles, generally. In other words, you can have two rifles of identical make and model and they can even be consecutively serial numbered and one may very well show a preference for one ammo type and the other will prefer something else. If you understand fully everything that is going on when you discharge a spring piston air rifle, the surprise isn't that this in the general way of things, but that sometimes, you do have RARE exceptions....
A good example is that most people that I know who shoot .20 R-9's find top accuracy in Beeman Field Target Specials. But that again is kind of exceptional and there are probably .20 R-9's out there that don't shoot FTSs worth a hoot.
Also, when you fully understand all that is going when you discharge a "springer," you'll understand why they generally don't shoot well when fired off a solid rest. Attempts at constraining these guns typically result in irratic groups. Proper springer technique involves a consistant hold that is the same from shot to shot and allows the rifle to freely recoil while maintaining proper follow through. And if that seems like "freely recoil" and "proper follow through" don't go together, you aren't half wrong.
There are some spring piston air rifles on the market that are capable of stellar accuracy that rivals a fine turnbolt rimfire sporting rifle -like Theoben Crusaders, for example. Getting all the precision that these rifles are capable of, however, requires a very disciplined shooting technique, and it is one that probably has more in common with shooting flintlock muzzle loaders than nitro-burning "suppository" arms. Also, just because you're the reigning smallbore champion at your local club, that skill level doesn't automatically translate to getting the most out of a springer. But, if you AREN'T the smallbore champion at your club, and WANT to be, mastering a spring piston air rifle will, in my view, get you a looooooong way toward that goal. You'll develop consistant technique that most cartidge arm shooters never see the need to work toward.
Finally, Gamo could do the world a favor and ship material in with their products that clearly explains why you probably aren't going to see anything close to accuracy with most springers until you've shot through a break in period.
In a nutshell, these guns typically come from Europe or Asia, or some other far off place. They're lubricated to prevent internal corrosion, and sometimes overlubricated for what you'd want in an everyday shooter. Until the excess lube burns off, and the seals start to wear in and seat correctly, you can and probably will have dieseling that isn't consistant from shot to shot. This in turn will cause blown pellet skirts and or uneven obturation in the bore. The effect of that is similar to a poorly crowned barrel. The projectile isn't evenly released from the muzzle, and yaw is introduced. Couple that with velocity swing, and patterns rather than groups are a predictable result.
Ditch the powderbuner benchrest technique. Shoot though the break in process with proper springer technique, and you'll very likely wind up being pleased with how your Viper performs.
-JP
