Leapers base for RWS Diana rifles - Part 1
How we began
by B.B. Pelletier
I've wanted to write this report for a long time, but I didn't want to get you all excited about something you couldn't buy. Now I hear that Leapers will be shipping the scope mount bases they designed for RWS Diana rifles in July. Since it will take several reports to cover these bases adequately, the time has come to break silence.
The year 2007 was busy for me. Besides developing the Discovery with Crosman, I was also working on this base. Here's how the project got started. Some time in 2006, I told a reader how to mount a scope on an RWS Diana rifle. That must have been the thousandth time I had to go through that litany, after which I had to convince him that these problems really do exist and then I recited what I had done to try to convince Diana that their scope base needed to be changed. Weary and desperate, I met with David Ding of Leapers at the 2007 SHOT Show and asked him to make this base.
My buddy Earl "Mac" McDonald was with me at that meeting, and his contribution turned out to be equally important. I just wanted a base that would provide a positive mechanical scope stop for most Diana rifles. I was tired of hearing that some people had sheared-off screws and long grooves cut through the steel bases of their rifles. The only way to positively afix a scope to a Diana spring rifle (with the exception of the models 46, and the Schutze), is to hang a vertical scope stop pin in front of the scope base. This looks dorky, not to mention the crudeness of having to do it that way. But the holes on the rifle's scope base are too shallow to hold a scope stop pin, and the large-headed screw at the rear has a thin shank that will not take the strain of a scope mount bearing against it under repeated recoil. If you're using that screw as a stop, you need to know that it will shear off.
This is what happens every time! The scope stop holes are too shallow and the pins rip out the back, cutting a groove backwards. This rifle had only 200 shots (approx.). The large-headed screw was already sheared off.
Don't butt the rear ring against the large screw head at the right. With the new base, you won't have to.
My contribution was the design of a plate that fits in front of the rifle's scope base. I even named the plate the recoil shock shoulder to convey the message of what it does. Leapers executed it beautifully, and you can't tell that their base is mounted any way but correctly. It just looks right. They radiused the bottom of the shock shoulder to conform perfectly to the spring tube diameter, so this base looks organic to the rifle. I also asked for a relief slot to protect the fragile large-headed screw from contact with the base.
Long job becomes short
Because the new base conforms so perfectly to the base on the rifle, it mounts in just seconds. The technicians at Pyramyd Air will find their scope-mounting time is cut drastically when they start using this new base. And, if that were all the new base did, it would be worth the money, but that's only half the tale.
Remember that Mac was at that meeting, too. After I made my pitch, he chimed in by asking if they could possibly engineer in a forward slope to cure the barrel droop problem some of the guns had. Oh my gosh! I'd completely forgotten that necessary step! Once you solve the anchoring problem, there may still be a barrel droop issue.
What is barrel droop?
Barrel droop means that the barrel's bore is pointing downward in relation to the plane of the scope base. When a scope is mounted, the barrel shoots noticeably lower than the scope looks. To compensate has always meant cranking up the elevation knob to bring the pellet back up to where the crosshairs are looking or inserting a shim. With some RWS Diana rifles, this isn't always possible or there's too much shimming that has to be done. Some of them have a large enough angle of droop that the scope cannot be zeroed at 20 yards, which is the most common zero point for most air rifles.
Diana wasn't convinced
For several years, I asked the management at Diana to fix this problem. Whenever I met them at the SHOT Show or at IWA, I would lobby for a change to the barrel droop problem. My suggestions fell on deaf ears. I'm sure I sounded like some airgun fanatic to them. After all, their guns were easy to sight in with the open sights that are installed on the barrel. What's the problem? They hadn't responded to the hundreds of people who called and wrote to ask what they were doing wrong. I had! Again and again, I told people how to either shim their mounts or, better yet, how to use B-Square adjustable scope mounts - mounts, I might add, that Dan Bechtel, the founder of B-Square, developed specifically for the airgun barrel droop issue.
So, when Mac spoke up, he saved the day. As long as a new base was being developed, let's solve ALL the mounting problems at the same time. Well, hearing that gave me another idea. Since this was just going to be a scope BASE, why not make it the best base we possibly could, which would be a Picatinny rail that accepts Weaver rings? That way, after the base was installed, the rings would just snap into the grooves and the mounting job would be complete.
That meeting lasted for 20 minutes, and David Ding decided right then that he would develop the base. I would test it and when it was ready for the market, the problem of scope-mounting a Diana rifle made after 1985 would be over. Instead of a 20-minute tutorial, all I'd have to do would be give the link to the part they needed.
In the next installment, I'll tell you about the testing I did. It lasted all year and pretty much revealed that this base won't be easy to copy. There's a lot more to show you and more that you need to understand about this base, so please stay tuned.