I have a Smith & Wesson MP2.0 compact in 9mm and have a Trijicon RMR mounted to same. I like the gun and use it for carry. However on occasion I get carbon/ soot that comes up via hole on the rear edge of the top of the chamber after the gun is fire that dirties up the lens of the optic. I suppose the hole is there to provide a view to see if the gun is loaded. It becomes rather difficult to see especially in low light when this occurs. . Anyone else have this issue and most importantly , is there a remedy?

I use lens cloths (the small ones that pack into the small bag with a key ring) and lens wipes to clean the optic window. An added benefit to lens wipes is many of them have anti-fog products incorporated into the wipe.

Interesting. In 2017 I bought a M&P 9L core. The gun turned out to be the most inaccurate handgun I've ever owned.Big disappointment as I really liked the gun otherwise. To remedy it I purchased an Apex 5" barrel for it. This cured the accuracy problem but introduced the very problem you described. I lost interest in the gun and pushed it to the back of the safe.

Fast forward to about two months ago. Finally sent it to S&W to see if they would fix it. Disappointed but not surprised as they say they returned it unchanged with a target that had a vertical string of four holes measuring 2.25" shot at 10 yards. Apparently they consider that acceptable accuracy. I shoot at twenty five yards.

So I tried Apex for the residue problem. Pleasantly surprised. After shooting them a picture of the chamber end they said it was missing a cut on the face of the chamber. They paid shipping both ways. Two days later I get a call from Doug. He says that's an early barrel and Apex has changed the material they're using and wants to send me a new barrel. Works for me. I installed it Friday and shot 200 rounds thru it. No residue. It's great when a company stands behind it's products. I wouldn't hesitate to buy from Apex again.

In comparing the factory barrel to the original Apex barrel you could see the angles of the bottom of the two hood protrusions were very different. Now in my case the sight was a Burris FFII. It might sit back further from the inspection port than your RMR. I have a RMR but it's mounted on an AK. I'd be interested to hear from someone else with an RMR on a M&P to see if they have your problem or does your barrel have an issue?

This apparently is a known issue with the M&P 2.0s and a variety of optics as documented in several online reviews and blogs.

The most sensible "fix" I've read to date is to treat your optic equipped M&P as a maintenance issue and clean the lenses after every range session.

Does it "solve" the issue? No.

But it does prevent excessive buildup.

Well that answers that. I just thought that much cleaning might wear off some kind of coating it appears to have on the glass.

I do not like the LCI for just this reason. There is a product called Cat cr*p, that will help by coating the lens, but especially with a RMR you will still get the carbon blown up on the lens. There is a company that makes a plate with a blast shield that I TE'd that really did do a great job of mitigating it. I can't remember the name, but have it at work if you would like to give them a try.
A SRO mounts more forward than the RMR and has less blast.

__________________
Plastic has no soul

Anyone make M&P 2.0 upgrade barrels that delete the mass hole? That would be a better cure.

Can't delete as half of the hole is part of the slide, at least it is on my 9L.

This may be the tail wagging the dog, but does anyone make an aftermarket barrel that deletes the loaded chamber indicator? Would that solve the problem?

I have not found one, but it would seem an aftermarket barrel with just a nub on the barrel hood to fill that void in the slide would go a long way.

An easier solution would be for Smith to eliminate the problem...but lawyers and all that.

__________________
Plastic has no soul

They could easily move this feature to the extractor, and just have it protrude a bit more to indicate the chamber is loaded.

The current method they use has been called a "Mass-hole" (dash optional.) So I assume this was something that was a legal requirement in Massachusetts. I don't know if it had to be a hole, or the extractor method would have been sufficient.

Since they are moving their HQs out of MASS maybe the hole will go away.
I have a compact 2.0 coming in and I plan on mounting a Holosun EPS on it and will see how it does.

I'm hoping this is not an issue as maybe different angles but if I had done more research I would have purchased the pistol to be a red dot host.

As mentioned, Cat Cxxp does help, protects the lens and makes for easier cleaning. I have used it for years and think of it like car wax.

The M&P CORE we haveis a first your core with the same type barrel and I kept a lens pens small bottle is cleaner and a lens cloth or more modern micro fiber rag for rifle scopes handy since 1973 and dot optics since the early '90's to cleans lens with . So your options are you can sell it or trade it ! . But some thing else . We have had a M&P core also for 10 or 11 years with RM02 on it but a holosun green circle dot today .

Smith isn't the only company that uses a hole. My P365 has a slot shaped hole. It only has fixed sights so I don't know if any residue is ejected.

I contacted S&W about the hole in the barrel and the issue with getting the red dot dirty.

Answers from two different S&W customer service reps they both told me that was the way the pistol was designed.

Calculated Kinetics makes the "Dog Tag" optic mounting plate that has a forward section that blocks the escaping gases from the LCI port.

__________________
SFC, US Army, Retired

I am an LE firearms instructor at an agency with a lot of M&P guns and a constantly increasing number of shooters using RDS. I'm also an RDS instructor. I have never seen the **** on the objective lens create any real issue, even on range sessions involving hundreds of rounds in a day.

But the lens does need to be cleaned. I recommend using a "lenspen" available at photo stores, using the brush side to remove any hard particles and the cleaner side to then clean the lens. I also recommend using Zeiss, B&W or similar lens cleaning fluid with a soft cotton or microfiber cloth. Clean, all-cotton tee shirts can be cut into small swatches and used. Don't wash with fabric softener, and use an extra rinse cycle. I also carry in my bag some Zeiss pre-moistened lens cleaning towelettes. They work fine and can be obtained from major online camera stores at pretty low cost per unit.

All of these work well and I have not seen them scratch a lens, but use at your own risk. I have not conducted any formal tests and am not responsible if you scratch your optic. Do not use tissue, clothing you are wearing, paper towels, napkins, etc., and I am reluctant to use Q tips.

The Calculated Kinetics plates look interesting, but I have not tried them and they won't be approved until we are sure they cannot interfere with retention holsters. I am tempted to obtain one for T&E purposes.

No one uses the LCI hole. I wish they would get rid of it. But I doubt they will.

__________________
I see dead people

The Calculated Kinetics DOGTAG mounting plate has a deflector between the LCI hole and the optic that eliminates about 80% of the problem.

Attached Images

DOGTAG.jpg (53.3 KB, 23 views)

I have a 5" ported core kit on my M&P 1.0. I also found a Storm Lake non ported barrel for it. I've never shot more than 150 rounds at any one time but never noted any build up on my RMR with either barrel.

Contacted Calculated Kinetics and placed an order for their "Dog Tag" mounting plate. I also have one coming from them for my Glock 45. Very curious about their products, more to follow I'm sure.

That was the name I couldn't think of earlier. It works pretty well.

__________________
Plastic has no soul

this was an issue with a Safariland 6290.. the plate was just a touch too thick to reliably release the ALS. CK was getting a couple ALS holsters to modify the plate so it would work.


And I agree totally on getting rid of the LCI.

__________________
Plastic has no soul

Can you modify the holster of do you need to modify the plate some how?

The plate on mine was just a little too thick to allow it to release. It might have been a tolerance stacking issue. If you are using a Safariland duty holster I would check with them, but I bet they have addressed it already.

__________________
Plastic has no soul