My first gun I had milled for an RMR. I just bought a different gun that came with plastic optics plates. There are aftermarket metal plates I can get but I’m wondering if it’s necessary. Are there any known issues with plastic optics plates?

I cringed when I read this post but then don't really have facts to back up anything cringe worthy. I would just be concerned about whether it would hold zero continuously based on some bias I might have for a plastic optic plate vs metal of which I have no previous experience with nor have I heard of any issues with them nor do I know anyone running a plastic optic plate.

I have the C&H Defender on my issued Glock 45 with a Holosun 507c green. The plate is polymer with a protector in front of the optic. Its been just fine so far.

This message has been edited. Last edited by: BennerP220,

Which gun?

Smith and Wesson ships their guns with plastic plates. The guns have screw holes for essentially everything they support in the slide itself and the plates essentially index the optic in the cut and provide some recoil support with plastic bosses.

Theoretically, there probably isn't anything wrong with it. C&H actually makes a polymer Glock MOS plate, but it's a much tougher polymer than I've seen in the S&W plates and uses metal T nuts (irrelevant on the S&W). The plates from S&W are pretty flimsy and on my one S&W CORE gun, I bought a metal plate from C&H.

When I evaluate an optic mount, one of the things that is important to me is how the plate fits into the optic cut. This gets into materials and process.

A machined plate is the gold standard. Cast plates (like Glock factory MOS plates) generally are not very precise both in actual dimensions and in flatness. Injection molded plastic is similar, but generally more forgiving. You'll see the Glock cast plates snap because they're brittle.

The injection molded plastic ones are more likely to conform, but the amount of support they provide is questionable. Softer plastics may allow you to over torque screws. Inaccurate molding may not make the plate flat (enough) and allow uneven support and torque and fatigue one screw over the other.

Screws are just a terrible thing to put on a handgun slide. Look at every handgun slide you've ever seen...nothing is screwed in. The closest thing are set screws on sights (and Glock front sights), which generally recommend or require thread locker and are relatively low load. Screws on adjustable sights are also common, but are again fairly low load and have a detent system. Asking screws to hold an optic down is already a lot, and a poorly designed plate that does not adequately stabilize the optic body in the pocket puts a lot of stress on the screw shafts as the screw is now asked to hold the optic in place in two planes.

So I guess the short answer on plastic plates, is that it depends. I think you can probably make a plate that is good enough, but honestly at $60 or $75, I'm probably going to just buy a quality, machined plate if it is available.

The polymer plates are better than the cast MOS plates because they can flex without breaking, but a well machined steel plate is the best but more expensive option.

quote:

Originally posted by DanH:
The polymer plates are better than the cast MOS plates because they can flex without breaking, but a well machined steel plate is the best but more expensive option.

The question becomes where is the force loaded if the plate flexes? Probably onto the screws. So you still potentially sheer the screws and get hit in the face by your optic, but at least you can reuse the polymer plate until your machined one arrives...

When you compare it to the MOS plates, if they flex a little they snap. Then again, any plate seems to be better than MOS plates.

I remember a lot of people poo poo the MBUS, when they first came out.

I picked up an FN 502 a couple weeks back and the plates are plastic.
On the 502 I can understand it because the mass needs to be kept lower to keep the gun cycling since it is a .22 and all.

As for larger caliber guns I don’t really see a huge issue just shooting. But say one has to do a one handed reload and needs to rack the slide then opts to use the optics as it’s push point.
I wonder how well the plate would hold up.

quote:

Originally posted by 12131:
I remember a lot of people poo poo the MBUS, when they first came out.

No doubt. Even to this day. I think they're more than proven.