Hi Surpmil, I actually did try to take the bridge off during my deep cleaning, but it has a couple recalcitrant screws. Rather than risk damage, I decided waiting was more prudent. I'm in the midst of a move bunkered down in a short-term rental, so the bulk of my gear (along with my penetrating oil) is inaccessible until the military's COVID-19 stop-move order ends. The photos are actually from before the deep cleaning, so that particular grime is mostly gone, but I'll definitely address it again once I'm settled in the new place.
One thing I have encountered though in messing about with snap caps is the rifle fairly consistently does not feed them correctly, driving them down into the front of the magazine rather than up the ramp. While it might be a snap cap-ism, as I have not tested with live rounds, it does seem like the magazine tends to tip them forward slightly even when at rest...