1) DoS regs...just can't run a BC or anything not approved yet on their guns. The SAW may be exempted since we don't run Sims through it.
2) When teaching, I like to tailor my set up to what the student's will most likely be using, ie... never taught a CCW/civilian course in a drop rig, won't run a SWAT school in jeans & concealment gear. As the BC is designed by and for entry teams, I have it available for them to run & test to determine for themselves if it is a viable option.
I do keep some commonality between my training guns & work guns. Teaching gun is more of a T&E platform.