Be cautious with optics screws

[GJM]

Last year, when I was working with Leupold on the Delta Point Pro, they were testing a Pro on their accelerated testing machine, and broke the two screws holding the optic to the fixture. Today, my wife was checking zero on a C More RTS 2 mounted to a 320 Legion, using a Springer Precision plate, when the zero seemed to move three inches. We looked at the optic and realized not one but BOTH screws attaching the C More to the Springer plate had sheared. We had recently mounted this optic to replace a defective Romeo 3 Max and had reused the Springer screws. Pictures below.

Moral of the story is to not reuse screws when replacing an optic, as they are a potential weak link. The sheared screws ruined the Springer plate, but that is better than if the optic was direct milled, and they sheared in the slide.

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[RAM Engineer]

So replace screws every time you change batteries?

[Alpha Sierra]

Last year, when I was working with Leupold on the Delta Point Pro, they were testing a Pro on their accelerated testing machine, and broke the two screws holding the optic to the fixture. Today, my wife was checking zero on a C More RTS 2 mounted to a 320 Legion, using a Springer Precision plate, when the zero seemed to move three inches. We looked at the optic and realized not one but BOTH screws attaching the C More to the Springer plate had sheared. We had recently mounted this optic to replace a defective Romeo 3 Max and had reused the Springer screws. Pictures below.

Moral of the story is to not reuse screws when replacing an optic, as they are a potential weak link. The sheared screws ruined the Springer plate, but that is better than if the optic was direct milled, and they sheared in the slide.

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How many tightening cycles did the screws on Leupold's test rig have? Those on your wife's pistol?

How tightly does the sight on your wife's pistol fit into the mount?

The CZ mounting plate on my gun needed some clearance on the front lip to let an RMR go in, and even then if the sight wasn't almost perfectly plumb it would jam on the recoil studs, that's how little clearance there is on that setup.

[MVS]

I have not broken any screws. Just a couple of days ago I did strip the head out of one trying to take a defective RMR on my Gen 5-19.

[Maca]

What was the torque on those screws? I have been using a vortex wrench to torque to 12 lbs.

[OlongJohnson]

Are they quality grade 12.9 screws (like those made by YFS in free Taiwan)? Or the finest Chinesium from the mainland?

[GJM]

I don’t how many cycles the DP Pro screws had, but it was being endurance tested on a special machine. It is interesting that the screws were the weak link for that test scenario.

I believe there were four cycles on the screws that broke today. I called Springer and they were very helpful. They asked me to remove the plate and check the screw length, and it turns out the screws were about a thread or so too long protruding below the plate, preventing optimal tightness, and allowing vibration which led to the shearing. They have another replacement plate and screws on the way too me already.

Long term, I wish the industry could standardize on a footprint like the Acro, and direct mill slides, so we could eliminate multiple failure points for shearing and stripping screws. I do think using fresh screws is a good approach when changing optics.

[NickDrak]

Any idea on the manufacturer of the screws? Lots of Taiwan (YFS) screws out there in the pistol mounted optics universe.

[GJM]

Any idea on the manufacturer of the screws? Lots of Taiwan (YFS) screws out there in the pistol mounted optics universe.

Will ask Springer the next time I speak with them.

[Alpha Sierra]

I don’t how many cycles the DP Pro screws had, but it was being endurance tested on a special machine. It is interesting that the screws were the weak link for that test scenario.
They had to have failed in tension, rather than shear, unless there were no recoil bosses/studs in whatever setup they were testing


I believe there were four cycles on the screws that broke today. I called Springer and they were very helpful. They asked me to remove the plate and check the screw length, and it turns out the screws were about a thread or so too long protruding below the plate, preventing optimal tightness, and allowing vibration which led to the shearing. They have another replacement plate and screws on the way too me already.
I kinda agree with you. Four cycles seems a lot to ask of such skinny screws (6-32?). Without knowing more about their metallurgy all one can do is err on the side of caution.

If your wife's optic's screws were too long, the only way they would not have developed enough joint tension is if they were bottoming out on something solid (like on the slide).

[BN]

Long term, I wish the industry could standardize on a footprint like the Acro, and direct mill slides,

They'll probably get to that right after they standardize iron sight dovetails. :(

[OlongJohnson]

Any idea on the manufacturer of the screws? Lots of Taiwan (YFS) screws out there in the pistol mounted optics universe.

In the world of gun hardware, YFS is an upgrade to a great number of parts.

[Erick Gelhaus]

Found this out the hard way with a T-1 - when going from from a LaRue mount and (yet again) re-using the screws to attach it to the stock, no elevation mount. Still need to get it to a machinist.

[NickDrak]

In the world of gun hardware, YFS is an upgrade to a great number of parts.

Direct (US made) replacement hardware can be sourced directly from McMaster-Carr for most applications.

[OlongJohnson]

McMaster doesn't list country of origin on the site, generally.

I just looked at the last order I have from them, still sitting on my work bench. Origin is marked on the boxes. SAE sizes are from US, except for a bag of washers that's "CN" (probably not Canada), and metric sizes are from TW. The coating on the TW screws is cleaner and more uniform, generally.

So it appears McMaster sources hardware from wherever seems best to them, just like Fabory or any other quality distributor.

H-K makes me happy, but I don't worry about a YFS mark.

[Alpha Sierra]

I don't care much about country of origin as long as I can get a cert and the country is on the DFARS list.

[TAZ]

McMaster Carr is your friend. You can buy a box of high strength alloy or SST screws of your liking for around $20 a box of 25. Thats 12 battery changes. Re-using teeny screws that are torqued and beat on by a reciprocating slide isn't saving you that much $$.

[CanineCombatives]

Agreed, can you specify torx over allen heads?

[GJM]

DP Pro just came loose on a Shadow 2 slide, direct milled by Primary. Screw broke.

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[OlongJohnson]

Maybe you need one of these:

https://www.amazon.com/Alden-4507P-Grabit-Broken-Extractor/dp/B000Q60UOO

[ssb]

Screws and MOS plates are why I decided I was willing to put up with the ACRO's shortcomings...

[miller_man]

DP Pro just came loose on a Shadow 2 slide, direct milled by Primary. Screw broke.

51268

Ohh, not excited about seeing that, have 3 slides done by them. Not that I think it is an issue with primary. Do you have a round count on that set up?

[GJM]

Ohh, not excited about seeing that, have 3 slides done by them. Not that I think it is an issue with primary. Do you have a round count on that set up?

The problem is the Leupold screw. Was a prototype ruggedized Pro, so it was in many different slides. I really need to change screws when I move it.

[miller_man]

Ok, good to hear that.

On the other hand, reading this thread has made me realize I have re-used two sets of screws when switching over to the SRO and moving my RMR over to another slide. I will look into getting some new screws, I may be switching over to try out a Holosun soon.

[MickAK]

DP Pro just came loose on a Shadow 2 slide, direct milled by Primary. Screw broke.

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Just out of curiosity, have you checked the calibration of your torque wrench recently? Doubt you haven't or that that's the issue but I've seen a lot of money wasted over tool calibration errors.

I think with the amount of money you appear to spend on these things you might look into retapping the threads so you can use the fastener that appeals to your specs instead of taking what they send you or finding something else that fits. What do you use for threadlocker?

[GJM]

Just out of curiosity, have you checked the calibration of your torque wrench recently? Doubt you haven't or that that's the issue but I've seen a lot of money wasted over tool calibration errors.

I think with the amount of money you appear to spend on these things you might look into retapping the threads so you can use the fastener that appeals to your specs instead of taking what they send you or finding something else that fits. What do you use for threadlocker?

I have loctite blue, red, 222 and the Vibra Tite stuff. Typically use blue loctite.

[MickAK]

I have loctite blue, red, 222 and the Vibra Tite stuff. Typically use blue loctite.

Well, there shouldn't be enough heat there to shake Loctite and I don't think there's enough vibration to require red. It doesn't look like a loosening to vibration failure either.

I'm not a good enough machinist or metallurgist to advise on what thread pitch/fastener material that could be changed to, but I would be surprised if a good sharp machinist couldn't find a good fastener and re-thread right quick.

[GJM]

Well, there shouldn't be enough heat there to shake Loctite and I don't think there's enough vibration to require red. It doesn't look like a loosening to vibration failure either.

I'm not a good enough machinist or metallurgist to advise on what thread pitch/fastener material that could be changed to, but I would be surprised if a good sharp machinist couldn't find a good fastener and re-thread right quick.

My first choice would be the Acro’s Mount, but after that a screw with a Torx 15 head would be my choice, with a bag of screws I changed proactively.

[MickAK]

My first choice would be the Acro’s Mount, but after that a screw with a Torx 15 head would be my choice, with a bag of screws I changed proactively.

Well, that's your call, and that might be a small amount of maintenance for the benefit gained, similar to oiling. I would like not to worry about the mount screws, and I'd like to see that engineered out. https://www.bakerrisk.com/wp-content/uploads/2015/03/avoiding-bolt-failures.pdf Not always possible but always ideal.