.
FWIW, You most likely have a worn cartridge stop that's causing "under the carrier" jams.
The cartridge stop is the vertical "finger" that extends upward from the forward edge of the lower link.
The tip usually wears down a few thousandths, and then a cartridge from the magazine will slip past it & under the lifter, making a partial disassembly necessary to clear.
While the link can be replaced, most knowledgeable gun enthusiasts just remove the link and either build up the tip with weld or swadge it longer via hammering on the side(s) with the opposite side on a steel flat.
It's been best practice to make the finger a little too long (NO cartridges will even feed from the mag), then file it down a little bit at a time until it just barely feeds OK.
This is the link, showing the front end:
Below (left) is a worn stop finger, below (right) is a typical finished repair:
.