Picatinny, Weaver & dovetail scope bases

by B.B. Pelletier

Today’s post is an answer to a question that came in last week. The reader asked, “What are the differences between Weaver, dovetail and Picatinny bases and rails?”

This is a question that a lot of airgunners and firearms shooters have and are unwilling to ask because they think everyone else knows the answer. I thought I knew and was surprised to discover a few things I didn’t know. For our discussion, the terms base and rail are synonymous.

Dovetails have been used by cabinetmakers for centuries.

Dovetails look like…well, the tail of a dove!
The dovetail is centuries old and probably originated with woodworking joinery. This is not a history lesson, but we are surrounded with antique furniture that’s held together by this joint. I believe the name originally came from the fact that the triangular shape of the joint resembles the tail of a dove.

The airgun dovetail is a parallel set of grooves running along the top of a receiver to which scope sight bases may be clamped. The width of the airgun dovetail is often quoted as 11mm, but in reality it varies from 9.5m to almost 14.mm! Not a lot of standardization there! However, modern airguns seem to conform to the 11mm size more than vintage guns. BSA is the notable exception.

This Slavia 631 has dovetails for mounting a scope.

B-Square publishes a free brochure on airgun scope mounts. It has a chart of the sizes for most popular airgun dovetails. B-Square is also the ONLY mount maker who has attempted to do anything about the variation in airgun dovetails. They have created airgun mounts that adapt to dovetails of varying widths and angles – something all other mount manufacturers turn a blind eye to. That is the reason that I usually recommend B-Square scope mounts over all other mounts on the market!

Get B-Square’s airgun mount brochure free!

Don’t use rimfire dovetails!
Rimfire rifles are also grooved for scope mounts. The industry settled on dovetails with a 3/8″ separation, which turns out to be surprisingly close to 11mm! But the mounts made for rimfires and sold in discount stores or gun stores are the lowest form of garbage! Never use them on an adult airgun.

Weaver mounts don’t work on airguns
Weaver mounts originated just before 1950. They were the first attempt to provide standardized scope mounts for rifles. They feature an integral recoil block to keep the rings in one place. Before Weaver mounts, rifles were most often drilled and tapped for small setscrews that sometimes snapped under heavy recoil. The Weaver base has a 3.8mm cross-key slot that accepts special Weaver keys located on the bottom of all Weaver rings.

Weaver base has cross slots that accept the keys found on the bottom of Weaver rings.

Weaver bases are great for firearms but too wide for airgun rings. Also, the locations of the cross slots are not standardized, so Weaver bases work best with two-piece rings. But, there is something even better!

The Picatinny rail is the most versatile of all bases
Picatinny Arsenal in New York is an ordnance arsenal. In the 1960s, they created a new type of scope mount for heavier weapons. It resembles a Weaver base, but the notches are 5mm wide and located at precise intervals along the rail. Any manufacturer can make a mount to fit a Picatinny rail! In the 1970s, Picatinny rails migrated to small arms use, and today they are widely used by the military and law enforcement to hold not only scopes but also flashlights, lasers, rangefinders and night vision devices.

The Picatinny rail is the most recent and the best of all three base systems!

Picatinny is not the same as Weaver!
This is where I became confused, because Weaver rings easily fit into Picatinny bases. The problem is that Weaver cross slots are smaller, which allows a lot of slop, so even though they do fit, Weaver rings are not compatible with Picatinny bases!

It’s academic to most airgunners
Since you won’t find Weaver or Picatinny bases on an airgun, they are almost academic, as far as airguns go. However, if you want to use a set of Weaver rings on an airgun for some reason, B-Square has an 11mm to Weaver adapter. In all other cases, you want 11mm airgun dovetail mounts.

Anymore questions? Let me know!

40 thoughts on “Picatinny, Weaver & dovetail scope bases

  1. I was looking into this very recently and learned that 3/8 rifel and 11mm airgun cuts are also at differnt angels! One is cut to grab flat withn the mount at 45 degrees and the other at 60 degrees. (I forget who was what) you can get a grab with a missmatch but not the friction that a correct fitting offers, and damage is likley.

  2. i was recently disappointed when i bought a du-10 , a set of scope mounts, a scope and a set of scope stops, only to find that the stops required a hole in the rail which the drulov did not have!

  3. Oh thank you so much. I just got my airsoft gun yesterday and it had a picatinny rail on it but the scope i bought for it came with dovetail rings. Thanks for helping me clear this up so i can get the right rings.

  4. I’d like to re-use some B-Square tri-ring mounts on an airgun with an 11mm dovetail. You mention the 11mm to Weaver adapter, but in looking at the B-Square catalog I also see a “Dovetail to Picatinney Adapter” (17015) on their airgun page. Since you say that the Pincatinny rail is the most versatile, it would seem that you’d prefer the Picatinny adapter, so why doesn’t PyramydAir offer that adapter? Because it’s not adjustable? That adapter doesn’t have “11mm” in the name, so perhaps it’s not for an 11mm dovetail?

  5. I went to the B-Square website to find what you mention, but it isn’t search-friendly. The new owners of B-Square are not experienced mount makers, so it’s quite possible they have fallen into the trap of calling an 11mm dovetail just a dovetail – disregarding the fact that Picatinny and Weaver are also both dovetails.

    If I had someone in the company to check with I would, but since they relocated to Florida in July I’ve lost all my contacts.


  6. Yeah, the B-Square website sucks. The best thing you can do to learn what products they have, independent of my question, is to simply download the PDF of their catalog and scroll through it. That’s where I saw the page specific to airguns with nice pictures of both adapters.

  7. what about open sights for these 11mm dovetails? where would be a good source for decent iron sights which utilize the 11mm dovetail?

    thanks so much for a great source of information… 3 years old and still a open topic of discussion. thank you.

  8. Paulo,

    You need a mount that no longer exists. The Slavia/CZ 630 is a wide 14mm dovetaiul that requires a cross-key.

    B-Square makes a 13.5mm mount for the Webley Patriot that will work because it has the cross key to mate in one of those three scalloped grooves on the top of your receiver. You will have to grind off one of the cross keys on the base of the mount to make it fit.





  9. The article helped me, but I'm still a bit confused. A scope I ordered a while ago came with some weaver/picatinny 1" rings, but I didn't use them since my air gun had dovetails. Recently I dug those up and decided to make a "tactical" light by putting a 1" flashlight in the ring and sticking it on one of my air guns. When I tried to put it on the gun, the ring didn't fit on the mount.

    I was trying to put it on a UTG barrel mount with weaver rails. The ring looks like it was made for something slightly smaller than the weaver rails, despite being advertised as a weaver ring.

    Why won't it fit? Is there some sort of adapter I can get to fix the problem?

  10. After further inspection I realized that they are the right sized rings, but they have a ridge in the middle between the clamps that makes it so that they can't go further than the very end of the rails, since the ridge goes in a groove. However, I see no way to get the ridge into a groove since the screw only comes out so far and I can't take one side of the clamp off.

  11. You may have noticed that Weaver dovetails have 3.5mm cross slots in them. Those are for a Weaver cross key that is part of every Weaver mount base. The ridge in the middle of the base is the cross key for the cross slot.

    11mm dovetails do not have cross slots for a cross key.


  12. I bought a cheapo red dot for my kids crosman m4. Didn't realize it had a picatinny rail. The sight has a dovetail mount. Does anyone make a dovetail adaptor that fits on a picatinny? All the ones I've seen are the opposite. Thanks.

  13. i would like to get a truglo red dot but will it fit into the ventilated rib of my A302 Beretta shotgun? If not, how can I solve the problem?

  14. Do you remember the model # of the BKL Drooper mount that you used on your Slavia 631? I have a European Slavia 631 Lux airgun with the wide 14 mm . I called BKL and the lady there swears that the only drooper unitized CZ Slavia mount that they have is the 200 series, which will only fit the 3/8" Slavias. She tells me that the 400 series do NOT have Drooper compensation but that they will fit the wide European 14 mm mount. What gives? She was not easy to talk to. I hate arguing with wimmen!-John-PS-Gotta e-mail address?

  15. John Waldron,

    Would a solution to mounting a scope on your drooping Slavia 631 Lux be to buy the BKL 400 series mount and either shim the scope in the rings or bend the barrel on your gun?


  16. Kdawg,

    No. What you are calling a "dovetail" (Picatinny rails are also dovetails) is an 11mm scope base and a Picatinny dovetail is 1/2-inch, which is much wider than 11mm.

    Leapers makes an 11mm to Picatinny adaptor, so an 11mm scope mount can be used on a Picatinny base.



    They call it a 3/8" adaptor, but 3/8" and 11mm are nearly the same, and it will work.


    • Aah! That’s what happened with my 3-9X40 AO with mounts included when it wouldn’t tighten up on my Airmaster I measured to see what the difference was and the gun’s is right @10mm while the mounts are closer to 1/2″ which is 13mm. Back to the rings game… one of these days I’ll learn all the stuff to look for to make sure this’ll work or maybe not.

  17. Does anyone know why manufactures insist on slash-labeling rails as Weaver/Picatinny? This is extremely annoying since they are not the same mounting rail. Also, very, very, seldom will one ever see a CAD drawing which would allow someone to make an informed decision.

    • Mah,

      It’s done for marketing. Weaver rings will fit Picatinny bases and with spring guns the recoil is all in one direction, so they work quite well. It’s similar to 3/8″ and 11mm rings being used interchangeably. They aren’t quite the same but they often do interchange.

      Real Weaver rings are not found in the airgun community that often. They remain the purview of firearms.


    • From what I’ve read, the main differences are:

      1) Picatinny defines a standard spacing for the cross slots, Weaver doesn’t define a slot spacing (so low possibility of moving a scope from one gun to another unless only one ring has the cross-beam — even then you may not be able to get the same relative position; the base for my Marlin 1894 has only two slots, one at each end)

      2) Picatinny slot width is defined a bit different — but the cross bars on Weaver compatible rings will fit Picatinny (for best results, one may want to make sure the rings have been pushed against the main recoil edge before tightening).

      While Picatinny rails are probably common — mil-spec Picatinny rings are probably not on the consumer market.

  18. Does anyone know what the most common picatinny rail size is? And seccond what scope would you recommend for a UTG L96 airsoft rifle which i have recently purchased.

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