FX Biathlon Mark I upgrades

Finally got some time to work on accessories for my Biathlon after I got the air leak fixed (been chasing that for the past year). 

So, I designed/ 3d printed a butt hook, and a magazine carrier with a spot to keep the foster probe. Still working on some issues like the top hook keeps spinning; thinking of either epoxying it in place or putting in some sort of grub/ set screw in case I want to adjust it.

Not the prettiest work I have ever done, but it seems to aid my high-heart-rate target shooting.