I intended to use a magnifier on an impending rifle project. To prove the concept, I used a Eotech/magnifier setup briefly during a range session yesterday.

A drill had a friend and I shooting three close range targets unmagnified, and then employing magnification to discern the proper simulated distant target to engage. There were three targets which were numbered in such a way that you could not read the numbers without magnification. The observer would call out the number to engage, after the three close range targets were shot.

I could not complete the drill a second time, after having done it once. The reason: the magnifier's lens had adopted a film of "exhaust" from the ejection port.

It did not take many rounds for this to occur. Not even half a mag.

This condition would likely be alleviated with a flip-to-center magnifier.

That's very interesting.
What magnifier were you using? (Perhaps it's something that should be obvious from what you posted, but I'm ignorant. )

Adjustable gas blocks have eliminated gas problems almost 100% for me.

Do you get a lot of gas to the face in general when shooting it suppressed?

It's a quality Aimpoint 3x magnifier. It's the older "grenade" style, but the optics are excellent.

I don't have an adjustable block on any of my guns, but they're all otherwise "tuned". The gun in question uses a rifle length gas system on a 16" barrel, a Sprinco red recoil spring, and an H3 buffer. It is not an unpleasant gun to shoot, gas-wise.

Another factor worth mentioning is the position of the sun. It was setting and at about a 10 o'clock position, relative to the target. Had the sun been above or at my back, the problem would not have been as exacerbated, and certainly not compromised visibility so bad so soon.

Another contributing factor is lubricant. I had lubricated the BCG prior to shooting, so it had the extra exhaust of the fresh oil.

Both these contributing factors are more-or-less unavoidable realities of practical shooting though.