by B.B. Pelletier
Barrel droop is a phrase that I believe was coined by Tim McMurray to describe the airgun barrel that points downward in relation to the top of the receiver (where the scope is mounted). It's been around as long as there have been airguns, but it was the scope sight that made it visible.
What is barrel droop?
From the name, you might suspect that we're talking about a barrel that somehow bends downward, but that's not the case. Barrel droop is actually a straight barrel that's been mounted in the receiver so that its axis points downward. There are bent barrels that point down, of course, but that's not what we mean by barrel droop.
Why does the barrel point down?
Good question. Why does the barrel of your Winchester model 70 point down? You say you think it doesn't? You're probably right. Yours probably points up! The point I'm trying to make is that almost no rifle barrel points exactly straight ahead in relation to the rest of the receiver and, more specifically, to the machined mounting pads where the scope bases go. Airgun barrels are the worst offenders, by far.
Come with me!
Take a close look at the Webley Patriot. If you've followed this blog, you know I think a lot of the Patriot, but look where the front sight is mounted. It's on the end of the barrel, isn't it? Where's the rear sight?. It's on the OTHER END OF THE BARREL! You may not be able to discern that in the photos, but both sights are mounted on the barrel. This is a breakbarrel rifle. That means the barrel swings down through an arc when the gun is cocked. The sights maintain a perfect relationship with each other because they both move. So, naturally, the gun shoots to where the sights are adjusted. If you mount a scope on the Patriot, where does it go? On the back of the receiver - the part that doesn't move when the barrel is cocked. So, a scope will be sensitive to where the barrel points, while the open sights just ride along with it.
But it's not that simple
Let's now look at an Diana RWS model 52. Because it cocks with a sidelever, the barrel doesn't move on this model. Plus, the rear sight is mounted on the receiver tube - not on the barrel. Know what? The RWS 48 and 52 have reputations for being droopers! Yes, they do. So, that fixed barrel that you thought would take care of everything didn't do all you had hoped, did it? Don't fret, though. The Weatherby Mark V that cost you $1,200 last year doesn't point straight ahead, either. You took care of that one when you sighted in your scope, and you'll do the same for your air rifles, no matter what kind they are.
Here's what's happening
First, the bore of your rifle does not run straight through the center of the barrel unless you paid a lot of money for it to be made that way. Second, all screw threads have room for fitting - called "tolerances." They cannot be perfectly machined and still go together, so if your barrel is screwed into your receiver, it isn't straight. If it is pressed in, as are most airgun barrels, it isn't straight either because the hole in the receiver isn't straight, which is my next point.
Third, the hole in a rifle receiver is not bored straight in relation to anything. What would it be straight WITH? Fourth, the grooves or mounting points on top of the rifle receiver are not straight with the receiver, except by accident. In short, in the world of manufacturing, everything is off by just a little. Usually, the amount they are off is so small that you don't notice it; and it's cancelled when you sight in. Sometimes, everything works together against you, and the rifle has a REAL problem!
The fact is that most of today's spring-piston air rifles point down to some extent. If the angle is small, you can correct it with the scope adjustments. If it's large, you need an adjustable scope mount. Tim McMurray sold a "Drooper" scope mount that corrects downward slant. For really bad rifles, there was the "Sooper Drooper." He had the rings bored out on an angle so they held the scope on a downward slant. It worked, but adjustable mounts came along and eventually proved even better. We'll look at them tomorrow!