# Leapers base for RWS Diana rifles – Part 2Testing

by B.B. Pelletier

Part 1

In the beginning, we learned a lot
When I started the Leapers base for RWS Diana rifles development project, I didn’t know what all the variables would be, but that is to be expected in the beginning of any development project. Often, something that sounds dirt-simple will surprise you with nuances and variables you couldn’t imagine before doing a little testing. Which is why the first two batches of prototypes I tried were complete failures. But, we did learn a lot of useful things from them; the most important was that an obvious approach toward making this base will absolutely not work. I’m not going to explain what we discovered, because Leapers deserves some consideration for all the effort they put into the project. It’s enough to say that the obvious approach to solving this problem of barrel droop on Diana rifles does not work. Learning that lesson added several months to what I had expected to be a quick development.

What range would work?
Once we did discover a method of droop correction that worked, we uncovered several more surprises. Leapers allowed me to control the technical specs we were after, which shaved a ton of time off the development. I didn’t have to test anything to know the ranges we were after with this base. I knew we wanted an initial zero of 20 yards, which will put all of these rifles back on zero at 30-36 yards. There is no other distance at which the trajectory is so flat within the useful range of any of the Diana spring rifles.

No two scopes alike
Now what I mean by “an initial zero of 20 yards” is that I wanted a scope base that put the scope at zero at 20 yards when the vertical reticle was adjusted somewhere near the center of its range. Every scope on the market has a different amount of adjustability range (the number of inches of adjustment from one end to the other), but they all have a center. If I could determine the best slope for every scope, so that no matter what scope was mounted they would all be approximately in the center of the vertical adjustment range, then airgunners would have the maximum number of clicks in both directions once they’d obtained a 20-yard zero. And, since the 20-yard zero really puts them on target from 20 to 30 (or even as much as 36 yards), depending on the velocity of the rifle and the pellet style used, this setup would give them the absolute greatest flexibility with their scope, regardless of the make or model.

Not everyone is an airgunner
This is not an insignificant fact. I have heard through the grapevine that some European designers have worked on a similar problem and selected 10 meters as their initial zero point. Ten meters is the worst possible zero point, because the scope and the barrel are not in alignment and must be made to converge. The scope has to be slanted downward to intersect the pellet in flight. By choosing a 10-meter zero, a scope would have to be on such a severe slant that much of its vertical adjustment would be wasted. You’d get only one or two yards with the pellet at the same height. With a 20-yard zero, the greatest amount of useful adjustability remains and the trajectory is the flattest over the longest distance.

What does useful range mean?
To determine useful adjustability, I took into account the fact that very few airgunners will ever attempt to shoot their RWS Diana rifles at ranges beyond 100 yards. In fact, very few will ever intentionally shoot past 50 yards. The fact that the gun will shoot farther is mitigated by the fact that nobody will use it that way. I selected the range within those limits over which the airgunner experiences the flattest trajectory, and they can adjust the reticle if they want to shoot at other distances. With that slope built into the base, the scope always has the adjustability for the other ranges.

A lot of drop!
When I discovered the amount of drop we had to build into it at 20 yards, it was stunning! The barrel was pointing so low we had to make a slope of more than 20 inches to get the scope to the center of the adjustment range with the reticle zeroed. I tested and retested to make certain the slope was correct, but it was. Then it hit me: What if all RWS Diana rifles don’t have the same slope as the RWS Diana 34 Panther I was using for testing?

In fact, no RWS Diana air rifle has exactly the same barrel droop as any other RWS Diana rifle. They’re each unique unto themselves. Diana doesn’t intentionally build barrel droop into each gun. It just happens because of how the rifles are designed…mostly how the breech is made. I won’t go into the reason why they’re like that because we don’t have time for it now, but a study of the design will reveal a barrel slope that’s consistent within certain limits. Unless the barrel has been intentionally bent, it will always droop within those limits. However, that’s true only for the breakbarrels.

Fixed-barrel droop
The fixed-barrel models also droop but not for the same reasons and not by the same amount as the breakbarrels, so I also tested the new base with an RWS Diana 460 Magnum rifle – an underlever rifle whose barrel is pressed into the receiver rather than into a pivoting baseblock. Because of this, the amount of downward slant may be more calculated than with the breakbarrel models. If the fixturing were totally random, I’d expect to find rifles that shoot high as well as low. While there are a few Diana fixed-barrel rifles that do shoot high, they’re rare compared to the number that shoot low. In fact, you can just about bet that a Diana fixed-barrel will shoot low, though the amount of droop is less than that of the breakbarrels.

Not everyone needs one
Many scopes can actually be adjusted for the droop that a fixed-barrel RWS Diana rifle has, and because of that there are a lot of airgunners who don’t even acknowledge the problem. Their scopes are all adjusted up nearly as high as they’ll go, but they’re on target and therefore satisfied. That may be all they need. If they never shoot beyond 40-50 yards, they may never run into the upper limit of their scope’s adjustment. Those shooters don’t really need this new base. But breakbarrel owners will hit the limit much sooner than fixed-barrel owners. Plus, everyone who wants to have some scope adjustment remaining will want the new base.

So what about the fixed-barrel owners? Do we give them the same base as the breakbarrel owners, or do we make a base just for them? The decision was up to Leapers, and they decided to do it right the first time. They made a second base just for fixed-barrel guns that was engineered to the slope I measured on the 460. I checked myself and tested the base on the 460 magnum as well as a sidelever RWS Diana 48 – another type of fixed-barrel Diana rifle. Like I said earlier, no two rifles will ever be exactly the same except by coincidence, but I did establish that the breakbarrels tended to be close to each other and so did the fixed-barrels.

Later testing
All this testing was proven in the third prototype which performed well, except that Leapers wanted to establish that the recoil shock shoulder was a better design than a vertical adjustment screw, so they built two different prototypes – one with the shock shoulder only and the other with the vertical pins only. Of course, by this time, there had to be a prototype set for breakbarrels and a second set for fixed barrels. I had to test both types of recoil restraint in the third prototype, and that added time to the development. In the end, the shock shoulder proved to be the superior design, and the vertical pins weren’t needed.

I took the third prototype to the 2008 SHOT Show and talked with the engineer who was doing the design development at Leapers. We could have gone into production at that point, but Leapers wisely wanted to test the base as thoroughly as possible, so they built a fourth prototype that was essentially the finished base except for some cosmetics.

I discussed the third prototype with Leapers at the 2008 SHOT Show.

Fourth time’s the charm!
On the fourth prototypes and also on the production bases, Leapers put both types of recoil stop – the shock shoulder and the vertical pin. Shooters who feel more comfortable with a vertical pin can have one, though everyone has to use the shock shoulder. It’s really all you need. The base absolutely cannot move once it’s correctly installed, because the recoil shock shoulder bumps against the front of the rifle’s base and comes to a dead stop. It’s the same thing we did by hanging the vertical stop pin in front of the rifle’s scope base all those years. Now, there’s a huge bearing surface, and the new base very nicely conceals the fact that the shock shoulder is hanging over the rifle’s base.

I think in my next installment I will share some of the astounding test data with you (targets used to determine drop), plus I’ll give you a review of installation – what little there is to say. This new base is the fastest, most reliable scope mounting system ever developed for a spring air rifle, and it will cut your scope installation time in half or less. Far less if you were also using adjustable mounts to get rid of the droop.

Categories Education / Training

### 44 thoughts on “Leapers base for RWS Diana rifles – Part 2Testing”

1. I have made comments to Leapers but they seem to not listen, perhaps they will listen to you. We need a FT scope that has the yardage adjustment wheel marked (and can only move) from 10 yds to, say, 60 yds. It makes no sense having a scope that can focus to infinity…..this is a gun scope, not a telescope. I’d like a 36-40x and a 12x for hunter class. Perhaps the market is just not big enough, but air rifles need precision……not great distance.

2. B.B. have you had a chance to look at the peep sights for the A.F. rifles? I’m thinking about buying a set. Would you do a review or give me an opinion? Or maybe ask Paul to throw that in when he does his H.P.A. installment? Thanks from SavageSam

3. Think about what you are asking for. You want a scope so specialized that perhaps 100-200 will be sold. What company is going to do that? Even Premier Reticle only makes a few of each type of specialized modification.

At the 2008 SHOT Show I spoke about this very subject with the head of Swarovski Optics – the top scope manufacturer in the world. He was wondering how many scopes like this he could sell for \$1,500-1,800. When I told him 200 in two years, he lost interest.

And then you also want several versions of this scope. It’s never going to happen because there is not enough business.

However, if you examine field target scopes carefully you will see that they put at least 50 percent of their parallax adjustment range into the 10-50-yards sector. Leapers has put as much as 75 percent into that sector, knowing that deer and antelope hunters barely know what parallax adjustment is for. So there are scopes that have been optimized for field target use.

Airgun field target is a very small sport. There are fewer than 1,000 active competitors in the U.S. and there probably aren’t 15,000 worldwide. Compare that the any bother shooting sport like 10-meter which has 100,000 active competitors worldwide and well over a million individuals who buy the guns and shoot in solitary.

However, if an engineering analysis were done on a scope, it might be possible to turn an existing model into something close to what you want with little additional development. As far as I know, that has never been done in the scope industry.

B.B.

4. SavageSam,

No, I have not yet examined an AirForce peep sight. They are so close to production, yet they are not quite ready.

The last thing I want to do is make a report on a sight that isn’t what people can buy. Whenever I do that I always get asked when I’m going to test the production version.

So I’m waiting. I’m going over to AirForce today to pick up some things to test, and I will check on both the new sight and the Edge rifle it goes on, as I always do.

B.B.

5. B.B. enough of the dangling carrot.It seems everytime I go to the Pyramid site to order this Leapers mount the date of “in stock” gets pushed back.Can you tell us when this mount is finally going to be in stock?Thank-you.

6. progun,

Believe it or not, Pyramyd Air has a manager who calls these manufacturers on items like this and asks when they will be available. They are the ones who change the dates.

These things come across the Pacific in containers, and they often can’t determine the exact date to within better than a couple of weeks. They know when the ship will arrive but they can never tell how long it will take to get through Customs. Then it has to be trucked to Leapers and then shipped to PA.

Leapers was pretty positive about getting them here in July, so let’s give them a chance.

B.B.

7. Morning (almost) B.B. Interesting, I’d have thought the droop would be the same on all the Dianas. Beware the simple little jobs. The’ll suck up more time than a black hole. My 350 Magnum’s scope stop pin is almost sheared off so I’m looking FWD to the new base. A question on scope movement in the rings please. PA mounted it with a plastic shim on the back ring and put some type of “rubber” cement on the inside of the rings to keep the scope in place. What are the torque values for the scope mounting bolts? Do you recommend lock tite on them? Thanks much

8. Bruce,

I’m not aware that there are torque values for the Allen screws on scope rings. Just get ’em tight. And be careful when working on aluminum rings because they strip out easily.

Yes, Locktite blue number 242 is recommended on all scope ring screws.

The shim PS used is a piece of 2-liter pop bottle. They have found that good for shimming the rear of all RWS Diana scope mounts.

The rubber inside the scope rings is usually a material provided by the ring manufacturer. It is a special non-slip[ formula that stops the scope tube from slipping inside the rings.

B.B.

9. B.B.

It has always been a mystery to me why a reputable company like Diana would build barrel droop into their rifles let alone leave it as a random variable.

I’m inside the one week mark for picking up my Smith and Wesson 1911. Whoo hoo. Nothing like the anticipation of picking up a new gun. I had a look at it on Thursday when I filled out the paperwork for the waiting period and the Kimber master dealer on staff was fairly salivating. Haw haw. Now a couple of cleaning questions that come to mind. Surely, you don’t break in the barrel of a 1911 the way you do for a new rifle–especially with the disassembly that’s required. On the other had, why wouldn’t you since the discharge is the same chemical process? Secondly, do you recommend brushing the bore before the 5 minute soak with solvent or after?

Joe B. on Maui, what is an unconditional love program?

Matt61

10. Matt61,

There is no break-in as far as I know. Just shoot the gun.

As for the solvent, follow the directions to the letter. Sweets, for example, lets you leave it in the bore for up to 15 minutes, depending on conditions. Always follow the directions.

B.B.

11. A couple of questions:
1. This is a base only that does not include and rings, correct?
2. The customer is required to provide their own 1 or 2 piece rings/base(s) that will attach to the rail correct?
3. Can any brand of mounts, adjustable or non-adjustable, be used with the Leaper’s Diana base?
4. Are there any provisions on the Leapers/Diana base for recoil stop pins?
5. If not, what is to stop the mounts/rings from moving on the Leapers/Diana base from spring recoil? I understand the base will not move as it becomes “locked” to the receiver.
6.
nathan

12. Really appreciate what you’ve done to make this project happen BB … I bought an RWS 350 Magnum last Summer (my first “Grown-Up” Air Rifle) and promptly ruined the C-Mount that it shipped with … since then I’ve replaced it with one of the B-Suared adjustable mounts, but I’ve always felt that it’s a pretty weak system and in need of regular tweaking just to keep it in zero … I’d been wanting to upgrade my scope to something more robust but have hesitated due to not wanting to deal with the delicate nature of the scope mount … With this new base on the horizon, I’m now looking forward to upgrading to a much better optic and am looking forward to a much simpler, secure and solid mounting procedure.

No real questions here, just lots of kudos. Thanks again!

13. Nathan,

Have you read part one of this report? This base provides a Picatinney base for rings. Use two-piece rings, only.

/blog/2008/06/leapers-base-for-rws-diana-rifles-part-1how-we-began/

Look at the cross slots in the Leapers base. Then read about Weaver rings and look at their crossbars that fit into those slots.

/blog/2007/2/what-is-a-weaver-mount/

Ain’t no slippin’ possible with this mounting system.

This is a base, only, as it says in part one. You have to also buy two-piece Weaver rings, and I recommend medium-height Weaver rings because this base raises the rings high.

B.B.

14. Ash,

Like I said in Part 1, I did this project so I could have a good way of scope mounting to recommend to RWS Diana rifle owners. I was tired of explaining the work-around all those years, and I just wanted to point to a product and say, “Buy that.”

B.B.

15. Optically, I can’t see any advantage in restricting the parallax range of an FT scope — the markings are just that. It seems to me that any imprecision would come from variations in focal length in the objective, etc. I suspect that the larger objectives are needed for FT not only for brightness but also to reduce the focal ratio, keeping the depth of focus low (so that you can tell when you’re “there”). Unfortunately, shorter focal ratios require greater precision in manufacturing, and it wouldn’t surprise me if focal length were allowed to vary somewhat (not necessarily greatly) in order to meet combined requirements…FT is probably the least important market for manufacturers and about the only place a small variation would matter.

Perhaps they could furnish an un-calibrated wheel, which the user could mark to their particular scope. But don’t people do that already? Personally, I would hate a scope that couldn’t focus at “infinitiy”:). Maybe double-speed sidewheels like are used for telescopes sometimes would be useful.

16. BG_Farmer,

Yes, people do mark their own yardage on the scope. You absolutely cannot use the numbers engraved on the outside, because they are only sort of correct at one temperature range.

And you are also correct that this really isn’t a problem for FT shooters.

B.B.

17. Bb,

Excellent report on the RWS base, be glad when it’s availble. Have you finished the test on the Ruger Air Hawk? Also , how is Crosman coming along with the new upgraded Discovery if you know? I’ve shot and shot the Genesis and it’s quieted down. No more detonations. Took A hole tin of pellets. Broke an Bushnell Elite 3-9X40 scope (surprised me) and am now using A BSA 3-12X44 scope which is doing just fine up to this point. Getting nickle groups at 45 Yds. Another \$300 and I’ll have enough for the RWS 460
. Can’t wait.

BobC NJ

18. Bobh,

Still one more Air Hawk test to do.

I’m checking into where Crosman is with the Discovery.

B.B.

19. B.B.

Thanks for the 1911 info.

On the broad subject of scope settings, imagine a military sniper creeping through the bushes. Once he finds a target, he can laser it to get an exact distance, but then how does he convert this information into a sight picture? The airgun analogy would be the FT shooter who you said could register his scope for every single distance he is likely to shoot. But a military sniper can’t do this. I suppose there is some sort of estimation process with the aid of ballistic tables and reference zeros, but this seems awfully chancy, especially when the sniper can’t fire any sighting shots to be sure.

A tactical question. I keep reading that the main flaw of the Garand is the inability to top off the clip in a spare moment. My question for this case and for any tactical reload is what are you topping the clip off with? Do people actually carry around loose rounds to reload their guns during a fight? I could see reloading a full magazine, but then there would be no problem with the Garand. I keep hearing this objection about the need to top off magazines, but as one who has never come close to a tactical situation, it makes no sense to me.

Matt61

20. Matt61,

A military sniper uses the same sidewheel scope that field target shooters pioneered. And they have ballistic correction charts. Even ballistic correction scopes. Remember, they only shoot one kind of ammo, so a ballistic solution is simple.

Yes people top off magazines. Take the M16/M4. It holds 20 or 30 rounds, but the rounds come on 10-round stripper clips, so you can top off a magazine. And yes, they do carry loose rounds to top off. Every country taught its soldiers to top their rifles off before a suspected enemy charge. That was very important in Korea when the Chinese did human wave charges.

Back in WWI, most rifle wwere equiped with a magazine cutoff, so the rifle was used as a single-shot while you were in the trenches, but flip the switch and the whole mag was available in an instant.

B.B.

21. B.B.–Scott298 reporting in(and always say hi to mom”). With my 350 I have been using b-square single piece adjustable mounts with a leapers scope. I’ve shot over a thousand of rounds with this set up and from time to time have had to adjust the rings to get the gun back to zero. I have never sheared a screw off- have had the scope or mount shift-guess I’m one of the lucky ones. With this new Diana set up would you start your initial sight in at 20 yards and do you feel that the Diana rail with the rings you recommend be better than what I’m using now? Loved this piece as it really hit home! Now as far as other guns with barrel droop I guess I’ll have to try viagra. Scott298

22. B.B.

Well, how about that. I guess it helps to have been out in the field. So some of those pouches in military gear were loaded with individual rounds; it’s not something that even an extensive action figure collection would reveal. I think the reloading of a magazine in the dark with fumbling fingers is asking a lot but maybe it comes with practice. Yet another reason to be happy that I won’t be facing a human wave charge.

I’m working through the Bullet’s Flight from Powder to Target, and I do believe I’ve discovered why that book didn’t get a good initial reception (so much that it led to the author’s premature end from disappointment according to the introduction). He needed an editor! Only a serious collector or gun historian would be interested in all of those obsolete models and calibers. But I will persevere with everything except for what is about specific guns.

Matt61

23. BB,
“A military sniper uses the same sidewheel scope that field target shooters pioneered. And they have ballistic correction charts. Even ballistic correction scopes. Remember, they only shoot one kind of ammo, so a ballistic solution is simple.”

The inference of your comment doesn’t make sense to me.

Do you claim a military sniper uses focus for range estimation?! I doubt there is much discernable focus difference between 400 yards or 2000. Parallel light rays don’t support this theory at those ranges.

Is range important to the sniper? Absolutely. Are trajectory charts useful? Yes. Do snipers range by focus adjustments? I’ve never seen anyone make that claim before.

24. B.B.,

Bill S.

25. Scott298,

The new Diana base will be better than what you have now in a couple of ways. First, it will take much less time to mount. Second, the correct slope is already built in so there is no need to adjust anything. And finally, there is no way the new base or the rings you put on it can ever shake loose.

B.B.

26. Matt61,

And 100 years from now, people will think an iPod and a Blackberry is quaint. Those calibers were well-known in 1914. Readers understood what Mann was referring to, though you are right that he needed an editor. His organization of thoughts leaves something to be desired.

B.B.

27. Military snipers are restricted to 10-power, so parallax isn’t too great a problem for them, especially at longer distances.

Law enforcement snipers use Leupold sidewheel sniper scopes. I never said they used them to rangefind, but perhaps the inclusion of a reference to field target was misleading.

B.B.

28. Bill S.,

Crosman is hard at work developing the second rifle in their PCP LINE. IT WILL NOT BE THE DISCOVERY.

IT WILL PROBABLY HAVE THE FOLLOWING FEATURES:

SHROUDED BARREL
REPEATING CAPABILITY.

B.B.

29. BB,
awww… we want more info on the new PCP that Crossman is developing. I understand that you may not have all the latest info but will this be a step up from the Discovery from a performance stand point?
I think Crossman has a winner in the Discovery and if they can build the new model from there (affordability, pump/CO2 features, accuracy etc) and improves upon that… I’m in!!!

30. Rudy,

Crosman will build on the fundamental ideas that went into the Discovery. When I initially told them my idea, it wasn’t for just one rifle, I gave them specifics on two models and a third model that I referred to but the specs were left blank. Every time we dropped a feature from the Discovery, like the shroud, for instance, they added it to the second rifle.

Features were dropped from the Discovery to keep the price under control. However, I have to say Crosman never in their wildest fantasies imagined how successful the Discovery would be. When they started getting a sense that the Disco was going to be a huge success, they immediately dropped any latent resistance they might have harbored for gun number two. They are on board and pulling hard at the oars, you might say.

I am not getting any info on the second rifle, other than the fact that it is indeed being developed. I expect it to be announced around the SHOT Show in 2009 and available soon thereafter.

I think they will retain the 2000 psi and dual fuel features from the Disco, and I expect to see all of the new features I mentioned before. There are some advanced things I suggested they do on gun two, but I’ll have to wait like everyone else to see if those came through.

B.B.

31. B.B.,

Thanks so much for the insight into the progression of development for the new diana scope base. It’s give me even greater hope for achieving the potential of the new diana 54 that I purchased with your direction. I’ve been frustrated with the leapers accushot one piece mount (unadjustable) that I purchased as a temporary solution until this new base is shipped to me. I’ve remounted the scope with the pin installed over the front of the base, added one more “shim” in addition to the one that pyramyd installed and still can’t get the scope (a new Leapers Accushot 3-12×44 AO SWAT) adjusted to anything closer than 3inches low at sixty feet. Even though I’ve read your info about optically centering a scope, I hope that this is all about barrel droop (drop) and hope that the new mount will fix this and eliminate my frustration. Hanging the stop over the front of the existing mount has also resulted in the scope being pushed very far forward and forced me to ackwardly “weld” my cheek on the stock. Looking forward to the new base. kevin

regards,
Jim

33. John,

The Air Hawk is one of the few riflse on which the BSA Adjustable mount might work well. Since nothing is behind it, You would have access to the elevation adjustment. Clamping pressure worked on my Air Hawk test, but I don’t know what would happen over a long time. That’s the only problem, because the rifle has no scope stop, as you know.

B.B..

34. B.B.–Scott298-Upon ordering the Diana scope base what scope rings would you recommend for my 350. I have a leapers 3x12x44ao with a 30mmtube–thanks –Scott298

35. B.B,

Re: Scope rings for the new base you helped design for the diana rifles

36. Kevin,

B-Square used to make adjustable rings with Weaver bases. I know because I own a set in both ring sizes.

But after they were sold, they started eliminating products from the line. They don’t seem to have what you need, so those Millet rings sound good at this point.

B.B.

37. B.B,

Thanks again. Wish B-Square still made the adjustable rings for weaver bases. Also wish B-Square still made the scope level that would work on your new base. kevin

38. B.B.,

Sorry to be such a bother. I’ve been looking for a scope level that will fit your new base. I haven’t been able to find a scope level like the B-Square you recommend for other bases. The only thing I’ve found is the microlevel sold by Longshot (www.microlevel.biz) that attaches to the scope. Have you had any experience with this device? Pro or con? kevin

39. Kevin,

Yes, I have tested the Long Shot and it does work as advertised. It adds some length to the back of the scope, however, so plan for that.

B.B.

40. B.B,

Thanks again. Looks like it adds about 1″, should be ok. kevin

41. B.B,

Your new base for the Diana rifles has shipped from pyramyd air. You promised another installment (Part 3?) for this base where you “will share some of the astounding test data with us (targets to determine drop), plus you’ll give us a review of installation – what little there is to say.” You tested your (and Mac’s and leapers) new base on the 34 panther and the 460 magnum. Did you test this base on a 54? kevin

42. Kevin,

Yes, it is time to do the third installment. Also, look at the new video that Paul Capelleo has done on this base.

I did not test the base on a 54, but I did test it on a 460 Magnum.

B.B.

43. B.B.,

Thanks for the third installment of your scope base. Watched Paul Capelleo’s video and read your installation instructions. I especially like his plug for your articles in the video. Looks like any idiot can install this base and securely mount a scope once and for all on a diana rifle so the odds are in my favor of accomplishing this task. kevin