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Posted: 1/5/2002 9:05:01 AM EDT
[Last Edit: 1/5/2002 9:07:00 AM EDT by NYPatriot]
There is a rumor floating around that the NATO standard Picatinny rail specs. have been changed (made slightly larger), and that the only commercial manufacturer currently making flat top AR15 upper receivers with the new specs. is Rock River Arms.

Anyone hear anything about this, and can anyone out there provide hard factual data that the Picatinny rail specs. have been officially changed?

Link Posted: 1/5/2002 10:28:25 PM EDT
From what I understand, everybody makes picatinny rails to their own specs.
Link Posted: 1/6/2002 7:16:39 AM EDT
Actually, Weaver rails are made to any specs you want. Picatinney is an actual specification that provides ALL dimensions. Failure to meet any dimension results in - a Weaver rail.

Link Posted: 1/6/2002 11:00:28 AM EDT
This is IIRC, so bear with me.

jimmybcool is correct - the spec for picatinny rails is ALL dimensions. The width dimension is +/- a few thousandths and the RR receivers are on the high end of the scale, but within milspec. Current milspec is the same - unchanged.

Tate
Link Posted: 1/6/2002 9:52:44 PM EDT
???
Link Posted: 1/6/2002 10:01:10 PM EDT

Originally Posted By jimmybcool:
Actually, Weaver rails are made to any specs you want. Picatinney is an actual specification that provides ALL dimensions. Failure to meet any dimension results in - a Weaver rail.




I recently read somewhere that a guy had trouble mounting his Weaver rings to a Picatinney rail, the result being "looseness".
Should we stick to Weaver/Weaver and Pic./Pic. to get the desired correct fit?
Link Posted: 1/6/2002 10:16:37 PM EDT
Link Posted: 1/6/2002 10:26:50 PM EDT
Troy, thanks for clearing the haze of misinformation for us.

What amazes me is Rock River Arms is apparently telling those who have purchased their flat top uppers that their mounting rail is machined to the "new" spec., and that all the other manufacturers will soon follow suit.

It would seem that, in reality, their uppers are out of spec., and they don't want to admit it.
Link Posted: 1/6/2002 10:34:15 PM EDT

Originally Posted By NYPatriot:
Troy, thanks for clearing the haze of misinformation for us.

What amazes me is Rock River Arms is apparently telling those who have purchased their flat top uppers that their mounting rail is machined to the "new" spec., and that all the other manufacturers will soon follow suit.

It would seem that, in reality, their uppers are out of spec., and they don't want to admit it.



Now I remember why I keep recommending Bushmaster.
Link Posted: 1/7/2002 12:56:19 AM EDT
Link Posted: 1/7/2002 2:05:47 AM EDT
Troy a lot of NV gear now uses the 1013 rails, there are retrofit kits to switch even the old AN/PVS-4 and TVS-4 to rails. The only units that have the old mounts are those that have yet to be issued flat tops or MWSs.
Link Posted: 1/7/2002 3:33:42 AM EDT
[Last Edit: 1/7/2002 5:34:49 PM EDT by QCMGR]
The Geometric Dimensioning and Tolerancing (GD&T) callout uses the M modifier. This specifies perfect form at MMC or max material condition. The tolerancing calls for .006 from the C datum at MMC using a TOP (Tolerance of Position Modifier). TOP for an external FOS (Feature Of Size) equals MMC (.835) pulse the TOP tolerance value. (.006) This tolerance is applied to the virtual condition boundary 90 degrees to datum plane C and centered between the basic dimension. The part will look like this:

The width of the rail is .835 - .005. MMC is .835 and LMC is .830 with TOP callout allowing for .006 float centered 90 degrees from the C datum at MMC centered between the basic dimension. This arrangement would yield a bonus tolerance of .006 at MMC.

Bottom Line:

The rail can be a maximum of .841.


If you download the print, it has a new rev. date.

In reality, you would want to stay close to nominal. The comments here indicate they may be running out of specification.
Link Posted: 1/7/2002 4:03:09 PM EDT
Link Posted: 1/7/2002 4:24:07 PM EDT
Link Posted: 1/7/2002 6:10:15 PM EDT

Originally Posted By QCMGR:
The Geometric Dimensioning and Tolerancing (GD&T) callout uses the M modifier. This specifies perfect form at MMC or max material condition. The tolerancing calls for .006 from the C datum at MMC using a TOP (Tolerance of Position Modifier). TOP for an external FOS (Feature Of Size) equals MMC (.835) pulse the TOP tolerance value. (.006) This tolerance is applied to the virtual condition boundary 90 degrees to datum plane C and centered between the basic dimension. The part will look like this:

The width of the rail is .835 - .005. MMC is .835 and LMC is .830 with TOP callout allowing for .006 float centered 90 degrees from the C datum at MMC centered between the basic dimension. This arrangement would yield a bonus tolerance of .006 at MMC.

Bottom Line:

The rail can be a maximum of .841.


If you download the print, it has a new rev. date.

In reality, you would want to stay close to nominal. The comments here indicate they may be running out of specification.



no chit huh?
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