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Discussion Starter #1
I have a Springer Precision mounting plate for my RMR on my AXG Scorpion. I'll probably need suppressor-height sights but want to keep them as short as possible.

Does anyone make a thinner plate with some kind of recoil management? This thing is about 0.19" thick.
 

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Discussion Starter #5 (Edited)
I thought AXG Scorpion allows direct mount of RMR without adapter plate.
Yes. All load bearing is on the screws though. While this is a carry gun and I don't bang the sight on a barrier to rack the slide, it's still pretty high stress.

So . . . two 6-40 screws with minor diameter of 0.106" . . . cross sectional area is 2 x 3.14159 x 0.106^2 / 4 = 0.018 in^2 . . . 120 ksi steel . . . 2160 lbs yield stress in tension

Figure . . . I don't know . . . 10% of that for an upper fatigue limit in shear? That's 216 lbs.

Guesses on top of guesses . . . 50 g's at an eighth of a pound mass . . . ~6 lbs applied load during recoil vs. 216 wildassguestimated capacity.

But then you have a load applied right at a stress riser, the threads, so the resulting stress right at the thread would be maybe 10x that. So you start getting toward 60 lbs (equivalent) applied vs. 200-ish capacity.

It's probably fine, just that I'm not terribly happy with depending on "probably."
 

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Yes. All load bearing is on the screws though. While this is a carry gun and I don't bang the sight on a barrier to rack the slide, it's still pretty high stress.

So . . . two 6-40 screws with minor diameter of 0.106" . . . cross sectional area is 2 x 3.14159 x 0.106^2 / 4 = 0.018 in^2 . . . 120 ksi steel . . . 2160 lbs yield stress in tension

Figure . . . I don't know . . . 10% of that for an upper fatigue limit in shear? That's 216 lbs.

Guesses on top of guesses . . . 50 g's at an eighth of a pound mass . . . ~6 lbs applied load during recoil vs. 216 wildassguestimated capacity.

But then you have a load applied right at a stress riser, the threads, so the resulting stress right at the thread would be maybe 10x that. So you start getting toward 60 lbs applied vs. 200-ish capacity.

It's probably fine, just that I'm not terribly happy with depending on "probably."
Oh, man, there goes the fun in bolting it on, squeeze the trigger and smell the gun smoke. 😊 You lost me with the very first ^ in your formula. Good luck.
 

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Discussion Starter #7
Well, what do we actually know about screws failing or sights losing their zero from movement?

Mention of it reported on this forum is my motivation for a plate - increased strength. I don't need it as an adapter.
 

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Well, I'm pretty new here. I've been trying to un-#$% this mess I have found myself in...

My AWESOME wife got me one of the early X-Carry units. ******* LOVE this gun. The more I shoot it, the more I love it. (coming from HK VP9 and M&P 2.0, and I think I was playing with a 1911 in the crib shortly after birth) Anyway... Wanted a threaded barrel for my X-Carry. Early inquiries showed "... for all but X-Carry". Didn't bother to ask why... Well, I find a Sig-made BBL (on sale) that doesn't have that disclaimer, so I buy it. It doesn't fit. ***?!?!? Get ahold of Sig.. this part was a bit of a gong show, but after sending the gun in... (why the SN wasn't enough to let them know) they email me and tell me the original X-carry units had a bull barrel, and the threaded bbl wouldn't fit in the bull slide.... they "offer me" a new slide (at a discount) so my threaded bbl will work. Goodness gracious..... OK, in a little bit of ******** here cuz I'm past the return window for the threaded barrel. Get the new slide, try to put the Romeo1 RDO on the new slide.... screw holes are just a micro-tad too big. (compared the cover screws to the optic crews with a Micrometer, and... ta-daaaa!)

So, I call Sig this morning, and... sure as shooting... they changed some things. So all this 'modular' crap is not nearly what it's cracked up - or advertised to be.

Found this thread, while trying to find a solution. The guy on the phone from Sig this morning tells me I have to get: 1) RomeoPRO, or 2) DeltaPoint to fit the new slide, OR... an adapter plate. GRRRRRRRR.

C&H may have one, but they are east-coast, and closed by now. Lakeside is not far from me, he emails back quickly, but does not make an adapter plate to go from "new" slide pattern to Holosun/Trijicon footprint. (BTW, Lakeside is a pretty cool premise, read their purpose on the website)

To say I'm kinda irritated at Sig right now (not cuz they had to make the changes to meet gov't contract, but because they didn't bother to tell me what the flying howler monkeys is really going on.) would be an understatement.

Reading EngineerScott's physics equations make sense to me. If I could find a couple of the right sized screws, I could mount the Romeo1 on the new slide, but it'd be just the screws locating it, and I'm not sure that's enough. Those various engagement bosses are there for a reason, and while I don't use my optic as a hammer, I'm inclined to agree with E-Scott about wanting some more strength.

Not sure I want to dump another $500 in a Leupold or RomeoPro, when I prefer the Holosun product and they are way less money. Not excited about an expensive mounting adapter either. Maybe this slide goes naked for a while....

PE
 

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Discussion Starter #9
Some of those companies will do a custom one-off.

The . . . uh . . . "non-standard" nature of Sig had me wait till I had gun and sight in hand before getting a plate. And I also contacted Sig and Trijicon directly. I found it difficult to sort on Springer Precision's site so contacted them. They nicely directed me to one of their products that would work.

So you might try contacting companies in question and get the specific requirements from them. Web sites don't even close to get into the detail you need for navigating minor design changes.
 

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^^ Thank you :) After all the hassle, that's the plan I'm trying to pursue. :) I got long-winded in my post, but most of that was to share that Lakeside (by his own statement) doesn't seem to have what I'm trying to find.

... sure wish they would all just agree on a standard footprint, in the interest of customer service, and consumer choice. Reminds me of the bolt-pattern issues on the pickup trucks..... they all gotta be 'speical'....

PE
 

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The answer is the CHPWS filler plate. Recoil bosses stem from the RMR's original intended application as a rifle mounted red dot, where there was no material to retain the optic within a slide cut. The optic was made to accept recoil bosses for rifle mounts. In a slide riding application, a direct mill should provide sufficient fit to prevent recoil from fatiguing on the fasteners. With the 320 optic cuts you can achieve a similar fit to direct milling using the filler plate, and it does appear to also feature recoil bosses. It wont be quite the same as a direct mill (especially in depth of mounting) but it does provide an effective shim to ensure the screws are not being loaded with shear stress.

We do know that lack of a filler plate or recoil bosses on relatively loose optic cuts has caused optics to lose zero or come off guns in training classes but often these are improperly torqued and/or substandard fasteners. It is not incredibly common, particularly with the plethora of tight optics cuts and good quality fasteners and mounting components. It really becomes a problem when people cheap out, particularly on fasteners, but also on mounting solutions. Provided you don't cheap out, all will be fine. But the filler plate for $55 is good peace of mind.
 

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Discussion Starter #12
Thanks all.

For what it's worth I asked Trijicon about it. They said, in part. "The locator pins are extremely important to the mounting of the RMR®. This reduces stress on the screws avoiding failure, and maintains the zero." They "strongly recommend" using a plate such as mentioned above.
 
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