[MadMax]

A longass time ago (when the TM P90 was still pretty new) I heavily modded one for myself. I was attracted to the TM P90 because the upper receiver is so well registered to the barrel. I really liked how I could register my optics to the barrel via the P90 upper assembly which offered great consistent alignment of the barrel axis within the assembly.

I hated the mags. I addressed this by doing something ugly. I sawed off the entire upper sight rail and gantry so I could stick mags together back to back. Initially I used adhesive backed velcro to stick the mags together, back to back, so I could do a super fast flip reload by rolling the pair of mags. The tactical reload was excellent and I almost always found a bit of time to strip off the empty upper mag and replace it with a fresh ready mag. I later removed the velcro and stuck on some machined bits that would key my mags together kind of like a G36 mag.

I also mounted a stub of rail to the remaining chunk of front post at the front of the sight gantry to mount an RDS optic to. It looks goofy to have an optic so far forward, but the unusual mounting provided an unexpected benefit. With the optic pushed so far forward, I found that I could very quickly acquire the dot. An RDS emits it's dot rearwards in a narrow cone where the dot is visible. That narrow cone gets wider the further you get away from the RDS which means that all I had to do was get my eye somewhere in a bigger fatter circle cast by the dot that was pushed unusually far forward on the gun. It looked dorky as shit, but man that gun was fast.

I also swapped out the short stock barrel and replaced it with a M4 barrel hidden in a suppressor shroud. That gun had a lot of reach until it slipped out of my underarm holster and I dropped it out of a tree.