Shilen is known for match barrels, most are not chambered for true 5.56 NATO ammo and it could have pressure problems. Might be just over gassed or it could lose a primer and tie up the trigger, it’s happened.
Railed gas blocks won’t fit under a rail where it’ll be protected. If it’s not pinned it can get knocked around and turn into a manually operated single shot.
For an LE gun, think Colt 6720 type and work from there instead of starting with a target rig.
Or if a basic Colt is not what your after, try this.
https://sionicsweaponsystems.com/lawenforcement/patrol-rifle-three/Or here
https://sonsoflibertygw.com/shop/sons-of-liberty-m4-patrol-rifle/
