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Picatinny vs. Weaver

Discuss Leupold, Bushnell, Swarovski, Weaver & more. Need advice on a scope for your firearm? We can help!

Picatinny vs. Weaver

Postby wildblue on Wed Jan 21, 2009 7:40 pm

The recoil lugs on true Picatinny scope rings are much larger than Weaver style rifle scope rings to better fit the dimensions of MIL-STD-1913 (Picatinny) rails. The recoil groove on Picatinny rails is .206. Not plus or minus, but .206 if the manufacturing was done correctly. Weaver base recoil slots are plus or minus .180, again, depending on the manufacturer, and with a certain amount of leeway.

So, Weaver scope rings will fit on Picatinny bases, but Picatinny rifle scope rings will not fit on Weaver rails. That's how it's supposed to work. Unfortunately, manufacturers and consumers interchange the monikers, occasionally resulting in non-compatible components.

For instance, Leupold recently changed their superb Mark 4 rifle scope rings to fit Weaver bases, so they are no longer true Picatinny due to the reduced size of the recoil lugs under the rings. In another example, Burris XTR rings are marketed as Picatinny but they are not. They are Weaver. In another Burris twist, they label the XTB bases as Weaver mounts, but they are Picatinny mounts. Aimpoint is on the ball and calls a spade a spade. They offer scope rings for their top quality reflex sights in Weaver AND Picatinny.

Slowly manufacturers are starting to make all rifle scope bases Picatinny and all riflescope rings Weaver style to insure compatibility with all newly manufactured items.
wildblue
 

Postby Steven_L on Thu Jan 22, 2009 6:10 pm

That was part of a blog post I wrote a while back. Thanks for reading it.

http://blog.tacticalstore.com/2007/06/p ... -base.html
Aim Hard!

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Weaver on Picatinney -No, No!

Postby bearclawthedonut on Thu Jan 22, 2009 7:25 pm

Be careful with putting Weaver Rings on a Picatinny rail.

I've got a Kel-Tek, SU-16c with a builtin picatinny rail. I ordered a Zeiss Z-Point-Reflex Red Dot Scope back when there was some confusion about which mount system Zeiss was using. I assumed that the Zeiss red dot sight with a Weaver mount would work fine on my picatinney rail. Well it fit allright, just fine as the mounting bar on the sight was smaller than the picatinny slot. But this Zeiss red dot has it's own builtin mount - a clamp the holds the red dot sight tight to the rail. (Man that's a real painfull pinch if you catch the web of your thumb in that clamp.) I's a strong clamp allright, but not strong enough to keep the Weaver mount red dot sight from sliding back and forth in the larger picatinny slot.

The result was after eight or ten shots - you lost your zero. You had to keep rezeroing. What a pain. Finally, I had my gunsmith make a shim, he milled it precisely, to take up the extra space. Since then no more rezeroing. I've talked to others who have had this same problem with Weaver scope rings on a picatinny rail. Admittedly, the problem is worse on the KT, SU-16 as the receiver and the builtin picatinny rail are made of plastic. But be forwarned, Weaver rings/mounts will not work on a picatinny rail unless they are very, very tight - this pretty much elimiates many aluminum rings.

By the way the Zeiss red dot sight is great, but very, very small. Cool looking photo-cell that actually works. I've had mine for almost five years with the original battery. During daylight the battery only operates the controls (on/off/brightness of red dot). The photo-cell powers the dot.
bearclawthedonut
 

Postby Steven_L on Fri Jan 23, 2009 3:22 pm

You may certainly use a weaver style ring with a smaller recoil lug on a base equipped with the larger picatinny slots. Move the rings to the frontmost position before tightening. Recoil will cause them to want to move to the front, and they cannot. On a spring piston airgun you would move the rings to the rearmost position since the dual recoil wants to move the rings towards the rear of the gun. An alternative is to position the rings in the slots you want as far away from each other in the slots as possible, or as close as possible.

Even true picatinny bases and rings have some play. There is always room. They are not press fit. A common issue in mounting is too much tightening of rings and bases. If you were to use a torque wrench set at 65 inch pounds for bases such as Leupold Mark IV, Badger, Nightforce, etc., and then take the wrench off and use a standard socket wrench, you would be amazed at how easy it is to turn and tighten even more. 65 inch pounds is not a lot, and I generally don't use a torque wrench anymore because I usually give the bolts another quarter turn or so anyway. Same with ring screws. It's easy to get carried away, though, and shear off a base screw or crush a scope tube. Be judicious if you think you know more than a torque wrench.
Aim Hard!

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Rings to Base

Postby bearclawthedonut on Fri Jan 23, 2009 6:37 pm

Yes, as you suggest Weaver Rings can be used on Picatinny bases. But the rings must be mounted tightly to the bases, particularly on a semi-auto, such as the KT, SU-16 where you have both recoil forces and the auto operating forces transfered by the bolt/bolt carrier. These forces move both rearward and forward. This tends to loosen things, such as ring mounting screws and even scope mounting (to the rings) screws. The liberal use of lock-tight, blue works fine and can be broken (unscrewed) if necessary. I've never used a torque wrench to mount rings to bases - I just tighten as tight as I can with a large screwdriver (depending on the type of ring) - to no more screw movement. While this works fine for me, I would not let my brother do this as he has much stronger hands.

Scopes must be clasped firmly by the rings to prevent movement, but not crushed. I've never crushed a scope, but it is possible. Some rings I've used come with a paper like gasket fitting in the lower (some the top also) half of the ring below the scope that helps to firmly hold the scope in place, while lessening the likelyhood of crushing the scope. I like that system. I also like Burris Zee rings, they are made of steel and are nicely machined. Not like something comming from Bsquare. But Zee rings are a bitch to put on and take off! No disagreement here, just different viewpoints, different concerns.
bearclawthedonut