G.I. Milsim has their own line of .50 caliber specific loading systems.
Prior to the completion of the loaders, G.I. Milsim's guns were completed, so in order to test the guns G.I Milsim needed to retrofit other loaders for testing.
Some retrofits are very simple and easy, the retrofitted Revolution was simply a sized metal sleeve in the feed tube.
Although G.I. Milsim can't speak on behalf of other companies, the possibities and ease of retrofitting loaders is very very possible.
Just having gotten back from WC, I spoke to quite a few companies - such as Pinokio. With the drop in kit they have prepared a Pinokio will fit 50 shy of 1000 .50 cal paintballs with the nose! Insane! Imagine having that power off the break!