Difference between ARMS and Picatinny rails? 3

[Helepolis]

Hi all,

as the title states, what is the difference between the rails?
I found the correct dimensions for the Picatinny rail but nothing on the ARMS.

Thanks!

 

[JNieman]

Perfect is, indeed, often the enemy of good-enough.

 

[Nescius]

Sure, there's no disagreement about the function of the rail. It usually works for the intended purpose.

I would argue that if the drawing had no tolerances at all, nothing would change out in the real world. Why? The tolerances currently on the drawing are as effective as no tolerances at all...uninterpretable.

Modern manufacturing equipment can easily produce rail that is "close enough" with no human confirmation. Most rail is not checked and nobody cares. Rail that is checked...what drawing is it checked against?

This is all fine and dandy...until you are responsible for a 100% PPAP on a part with the 1913 profile. Then what? I gave up trying to explain to people that the drawing is bogus. As in most similar cases, just fill out the swiss cheese PPAP and submit it...so the customer can ignore it...along with all the other paperwork they fudge to follow their approved ISO plan.

 

[IRstuff]

"3.2.8.3 Bore sight Repeatability.
The XXX must be capable of repeating bore sight/zero after removal and re-installation on its supporting weapon. When set to the neutral position and mounted to an M4/M4A1 on the Picatinny Rail, and then fully detached from the secured bracket, the XXX final beam position shall be within 0.5 mrad of the initial beam position. "

That would be a 0.5 m repeatability at 1000 m; had the requirement been 0.125 m repeatability, I think we could have met that. The spec as written was only intended for a weapon where the max range would have been around 500 m. Nevertheless, assuming a low dispersion round, the odds of hitting center of mass are pretty good, had this been a rifle sight.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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