Archive for March 15th 2010

Dear Reader, there are a couple of things you ought to know about Your Humble Correspondent. The first is that I am a beady-eyed, unrepentant, not-in-the-twelve-step-program bookaholic. My wife claims that reading is my “real” hobby and that everything else springs out of that. I think she may be pretty close to the truth.

Second, I make most of my living as a writer by working with various high-tech and medical organizations. I have neither a high-tech nor medical background, and if there is a secret to my success, it is my curiosity. I simply want to know how things work, and I’m not afraid to admit my ignorance and ask “stupid” questions to get the answers I seek.

That same curiosity applies to accuracy sports, like airgunning. So the other day, hoping I could solve some of the mystery of what makes some airguns accurate and others not, I ordered a copy of Rifle Accuracy Facts by Harold R. Vaughn from Precision Shooting Inc. Vaughn was Supervisor of the Aeroballistics Division at Sandia National Laboratory until 1986, and he has an insatiable curiosity about why do some rifles shoot much better than others.

Chapter 5 in Rifle Accuracy Facts is devoted to “Scope Sight Problems.” In it Vaughn recounts how “A number of years ago I bought two expensive high-power variable scopes of a well-known brand that were identical. I noticed that my shooting accuracy suddenly deteriorated, and decided something had to be wrong with the scopes. The only thing to do was to mount the receiver in a rigid vise then jar the mounted scope and see if the reticule returned to the same aiming spot.” It didn’t.

He also noted in a table that the lower the recoil weight, the higher the acceleration in g’s that the scope would be subjected to. An experimental sliding-rail rifle with a recoil weight of 6.25 lbs was subject to 480 g’s, while a 13.2 lb. heavy varmint rifle suffered only 162 g’s.

Emboldened by this information, I called an advertiser in Precision Shooting that specializes in custom modifications to scopes for benchrest competitors. I explained to the owner of the company the problems that springer shooters (particularly those who are shooting high-powered springers with sliding rail anti-recoil systems like the RWS 54 and 56) sometimes have with shifting point of impact.

He said something that really surprised me: “I wouldn’t use a variable power scope for critical target work.”

When I asked why, he explained that in order for a scope to be variable power, there had to be some lenses within the scope that were free to move. When severe recoil hits those movable lenses, they can jostle around and disturb the point of aim. If the recoil is harsh enough, it is inaccuracy just waiting to happen.

So here’s the bottom line on all this: if you have been shooting a heavily recoiling springer (or gas ram), and you’ve been noticing your shots sometimes fall exactly where the gun is pointed and sometimes they inexplicably go elsewhere, it just might be your scope reacting badly to the recoil. As a result, you might want to consider changing to a fixed power scope like the Hawke Sidewinder Tactical 30mm 10X42 or the MTC 10×44 IRS. And if you are ordering a heavily recoiling springer, I heartily suggest purchasing a fixed power scope to go with it.

Til next time, aim true and shoot straight.

– Jock Elliott