Speedloader tubes are not working

Hit up a gun shop a while ago and picked up a bunch of gun mods and various magazines, including what I thought was a nice little double-whammy of a speedloader chute mod with a couple 8-round speedloader tubes. Problem is, they don’t work. Installing the mod onto my M1014 or my Mossberg 930 SPX (both with an 8-round capacity) works fine, loading the speedloader tubes with shells works fine, but loading the shotgun with the speedloader tubes just does not work, for some reason.

Has anybody else encountered this issue and, if so, can you tell me if this is a game problem or a me problem?

Shotgun speed loaders have been broken for a long time, and not lacking attempts to fix them too.