To me the cartridge stop doesn't look like it's close enough to the rim of .410, is it bent? or could someone have put in one from a 12 or 20 gage? Does it move as the action is cycled? I was going to pull out my 170 rifle, it would have a similar, or possibly the same, cartridge stop as a 30 in .410... but it's currently in the back corner of a safe. Someone with a 170 that's readily at hand should be able to help.
Part 27 here, but there is no individual listing for it -
30-series-c-410-gaPart 30 for a 170 -
sav/170-ser-aHere's a 20 ga one for a Model 30 -
products/399290D