Not to beat a dead horse, but I have some new and pertinent information. I was turning in a Form 4 to a local suppressor manufacturer and spoke with him at length about this topic.
I asked about shooting .22LR through a 5.56mm suppressor. Fouling or particulates from the .22 rounds aren't a problem for most suppressors. If a suppressor, like Gemtech for example, has baffling with small holes then these small holes or ports may get gummed up from firing .22LR, which is why Gemtech says you can submerge their single piece cans to clean them. I can't post a photo because Innovative Arms owns the design, it's patented, and they kindly asked me not to, but the IA baffle core is cut from a single piece of stainless steel. There are no holes besides the one the round travels through, and the shape of the cuts and the core altogether promote "self cleaning". Basically, it's designed so the expulsion of the round also blows a lot of the exhaust gas out with it. The owner told me if I were to fire several hundred .22LR rounds through the 5.56mm suppressor, that it would be recommended to fire 5-10 5.56mm rounds out after all the .22LR is complete to "clean" it. The stainless core is another reason you can shoot the suppressor wet with no problems. I would probably blow it out with my air compressor afterwards, but that's just me. Additionally, IA has suppressors that were purchased by a nuclear plant in SC who's security force has put over 30,000 rounds through with no problems. Direct quote from the owner/builder: "I build them so they don't have to come back here." Although it would be possible to cut the 2 welds on the can and remove the core for modification or repair, from what I've seen it will not be necessary. The core in these particular suppressors is rock freakin' solid, cut from a 1.5"x6" solid block of steel. Going to be tough to destroy that. There is a picture on IA's website regarding their .22LR suppressors and the core for their .22 Apex is very similar to the 5.56mm can only the .22 can is aluminum and the Grunt is steel. The picture is kind of small, so I don't know if the surfaces are polished on the Apex or grooved for extra sound wave destruction...I'd imagine the latter.
After the conversation and demonstration, I am fully confident about shooting .22LR out of any quality built suppressor.