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View Full Version : SU16 rail isn't Picatinny spec (MIL-STD-1913)


maxicon
02-22-2005, 9:09 PM
I've been playing around with rails, mounts, Swan sleeves, etc., and was a bit surprised to find that many folks don't follow the so-called Picatinny MIL-STD-1913 spec for their rails.
http://www.biggerhammer.net/picatinny/

It seems that a lot of stuff is designed to be Weaver compatible without being 1913 compatible. A Weaver mount is a design, Picatinny/1913 is a spec. Weaver slots and crossbars vary dramatically, even across different Weaver-brand products. Generally, Weaver bars fit in 1913 slots (loosely), but not all 1913 compatible bars fit in Weaver slots.

In particular, with the SU16's rail, the slots are too narrow and the spacing's too short as a result. This isn't a problem with most rings, which are designed to work with either Weaver or 1913 slots, but for any mounts that are designed for a tight fit in a 1913 or for 1913 slot spacing, they won't fit.

I have a couple of extended rails I wanted to try on the SU16 to move my scope further forward, and when one crossbolt is in a recoil groove, the other falls right on top of a stop. Same with an A3 carry handle; it just doesn't fit.

Likewise, the railed gas block on my new varmint upper isn't built to the 1913 spec (I'm still working on whether this is normal with the vendor, but I think it is).

Here are the key dimensions:
Design__Recoil groove_____Center-center
1913____0.206 + .008_______0.394
SU16____0.185______________0.375
Weaver__~0.155 (varies)____Varies

Recoil stop height varies a good bit from the spec of .118 +.008 (most I've checked are 0.100-0.110), but this isn't critical for most stuff.

So, it's a good thing to be aware of. One-piece mounts won't fit an SU16 if they've got two cross-bars designed for 1913 spacing. Two-piece mounts are likely to be OK, since most have a crossbar that's small enough for either, but you won't be able to switch them between a flat-top AR and an SU16 without moving the rings, which sucks.

You'd think this would be a no-brainer, but apparently not. Anybody know if the newer SU16s have gone to 1913 spec rails?

max

maxicon
02-22-2005, 9:09 PM
I've been playing around with rails, mounts, Swan sleeves, etc., and was a bit surprised to find that many folks don't follow the so-called Picatinny MIL-STD-1913 spec for their rails.
http://www.biggerhammer.net/picatinny/

It seems that a lot of stuff is designed to be Weaver compatible without being 1913 compatible. A Weaver mount is a design, Picatinny/1913 is a spec. Weaver slots and crossbars vary dramatically, even across different Weaver-brand products. Generally, Weaver bars fit in 1913 slots (loosely), but not all 1913 compatible bars fit in Weaver slots.

In particular, with the SU16's rail, the slots are too narrow and the spacing's too short as a result. This isn't a problem with most rings, which are designed to work with either Weaver or 1913 slots, but for any mounts that are designed for a tight fit in a 1913 or for 1913 slot spacing, they won't fit.

I have a couple of extended rails I wanted to try on the SU16 to move my scope further forward, and when one crossbolt is in a recoil groove, the other falls right on top of a stop. Same with an A3 carry handle; it just doesn't fit.

Likewise, the railed gas block on my new varmint upper isn't built to the 1913 spec (I'm still working on whether this is normal with the vendor, but I think it is).

Here are the key dimensions:
Design__Recoil groove_____Center-center
1913____0.206 + .008_______0.394
SU16____0.185______________0.375
Weaver__~0.155 (varies)____Varies

Recoil stop height varies a good bit from the spec of .118 +.008 (most I've checked are 0.100-0.110), but this isn't critical for most stuff.

So, it's a good thing to be aware of. One-piece mounts won't fit an SU16 if they've got two cross-bars designed for 1913 spacing. Two-piece mounts are likely to be OK, since most have a crossbar that's small enough for either, but you won't be able to switch them between a flat-top AR and an SU16 without moving the rings, which sucks.

You'd think this would be a no-brainer, but apparently not. Anybody know if the newer SU16s have gone to 1913 spec rails?

max

Technical Ted
02-22-2005, 9:23 PM
http://www.biggerhammer.net/picatinny/

Stevil
02-22-2005, 9:31 PM
None of the SU rails are to spec... God knows why BUT the great thing about SU's is they're made of Zytel... so break out the files and your Dremel and make 'em things fit damnit! http://calguns.net/groupee_common/emoticons/icon_biggrin.gif

maxicon
02-22-2005, 9:38 PM
Well, I thought about that, but I figure my GGG Scout Rail was $40, so I'll take the drill press to that first, and with that mounted, I've got a 1913-spec rail.

I hate to cut on a gun's receiver, but it would be nice to be able to switch stuff over. Only problem is I'd be taking out a whole recoil stop, leaving a triple-wide gap, but it's not like recoil's a big problem.

Still, it sucks. They could have done it right just as easy as screwing it up!

maxicon
02-23-2005, 10:41 PM
Another interesting tidbit, taken from a post over at www.ktog.org: (http://www.ktog.org:)

Someone asked Keltec about the Picatinny spec, and got this reply:

"Our SU-16 "A" & "B" models accept Weaver rings. While the "C" & "D" models accept both the Weaver and MIL-std 1913 picatinny rings."

Thank you,
Kel-Tec Customer Service


max

Stevil
02-25-2005, 11:54 PM
Yup, I was wrong, sorry. The C & D and you'd also suppose then the CA have MIL-SPEC 1913 picatinny rails. http://calguns.net/groupee_common/emoticons/icon_smile.gif