I use butt cartridge carriers on most of my shotguns & rifles , for the past 30 yrs. It is great way to do a fast reload , often with
just 1 more round or the 1st. round , if seeing game before you are loaded up.
I specifically remember doing a fast load of 1 round into a unloaded rifle , when seeing game . I would have missed that deer
without that fast loading from the carrier . I often use tube mag levers.
I may have lost the odd round over the years , but so what ,,,,,,,,, the value of the carrier far outweighs any lost rounds.
That is my experience .