I was curious after reading in another glock thread about the potential issue of Gen5 guns getting hot enough to affect an attached slide mounted battery powered optic.
So tonight I took a few measurements using IR Temps. A minor disclaimer is that emissivity is a real issue in measuring stuff like this and I didn't try to adjust for it in any way. SO these are probably just indicative temps and not precise, but given the values and my goals it doesn't make any difference.

Starting temp of the barrel 54.5F
Starting temp of the optic 60.1F (I don't know if it generates a bit of heat itself or where it sits in the holster means I heat it a bit)

After 100 rounds fired at an fast but aimed pace (approx 1/sec, 5 mag changes)
barrel 160.7F
optic 62.4 F
at this point you could touch the barrel briefly and hold the slide without difficulty.
I was surprised at how little it had increased.

So after that measurement I shot another 50 rounds again about as fast as I could while still holding the dot on the target.
barrel 200.1F
optic 64.5F

I didn't have any more loaded mags so I loaded up another 25 rounds and then fired them.
But in the interim the barrel had cooled (slide was locked open) and those temps did not exceed the previous high.

I can't imagine what I might do shooting that would substantially increase these temps into the danger zone for the optic so I have ceased worrying about my RMR.
FWIW>

“One accurate measurement is worth a thousand expert opinions.”
— Grace Murray Hopper, Rear Admiral, U.S. Navy

Thank you!

That's good stuff. Thank you.

It is interesting how little temperature shift the optic had. I would have expected more heat transfer.

I measured the barrel at the very end of muzzle in the above. What was interesting is that when I measured the barrel at the breech end that the temps had not climbed at all versus the slide. So I think heat has to go from the barrel end (very small contact area with the slide), raise the temp of the slide (which it does but large mass versus the barrel contact point) and then get to the optic.
Edited to add. In all of these I shot then locked the slide to the rear so I could get the thermal camera to measure the barrel. It may be that if I let the barrel heat soak the slide by leaving the slide closed more might be transferred to optic... I'll actually measure that the next time I can go shoot and test.

You could also let it sit after heating her up good and measure every minute until things stabilize. I'd expect the slide and optic to keep getting hotter for a little bit.

quote:

Originally posted by sigfreund:
“One accurate measurement is worth a thousand expert opinions.”
— Grace Murray Hopper, Rear Admiral, U.S. Navy

Thank you!

Ain't that the truth. You've got morons on the internet wasting their and everybody else's time positing stupid theories look the one that appears to be disproven here. One guy can take a few minutes and a thermometer and prove it wrong.

Makes me want to go out with one of my Glock full auto conversions and see what happens... Except there are no shortage of Sage Dynamics videos running various Glocks and optics through 500 rounds in just a few minutes to prove that this is a non-issue.

Good work, OP

If I understand correctly, your test pistol is a Glock 19X. The 19X has a PVD coating, different from the nDLC finish on regular Gen 5 pistols.
The theory I have heard is the nDLC finish is causing the hotter temperatures. While I am not sure PVD vs nDLC would much change the optic temperature, it seems like you wouldn’t want to use a 19X for your experiment.

More than optic temperature, I would be interested in you comparing a PVD 19X to a Gen 5 19 with the nDLC slide finish.

I'll run the same on a Glock 45 as a matter of curiosity. But I really don't give a hoot what the glock temp is, I want to know what is transferring to the optic which is the most sensitive part. There may be IR measurement issues with barrel and the various coatings, but the optic is plain black aluminum and the readings are probably pretty good. In addition one could easily handle both the slide and optic in bare hands so I am completely confident with these volumes we are not transferring any material amount of heat to the optic.

Hrcjon, I had posted a quote and a link here in regards to emissivity measurements that someone else did on another forum. Seemed that it was important. My post was deleted; I presume I violated some rules.. If you're curious, pm me.

I'm gonna make a SWAG here and say that unless you are firing almost non stop except for magazine changes it's going to be very difficult to overheat the slide cut mounted optic on a modern semi auto pistol. The barrel is where the action is, and the slide really doesn't have enough contact surface to transmit that kind of heat.

Who did the RMR cut?

Parker Mountain Machine in NH.