Whats the difference between the Alpha Rail (the model without the built-in sight) and the TRX?
The Alpha (i think) uses the standard Barrel nut. Does the TRX?
The Alpha rails utilizes the standard barrel nut.
The TRX Extreme uses a proprietary barrel nut.
From Troy Industries
...proprietary rotary locking system utilizing Troy's proprietary barrel nut
The way they attach to their respective barrel nuts are different as well.
The Alpha rail uses 3 clamp screws that interface with the standard barrel nut.
The TRX Extreme has 2 screws set in to helicoils on a locking tab.
That's correct. The Alpha rail system is an improved version of the TRX that uses three internal clamps that lock against the standard AR-15 barrel nut. The TRX uses it's own proprietary barrel nut with a clamp locking system that squeezes the handguard around the barrel nut. Thank you!
Have the problems with the loose front sights on the alpha rails been corrected? Also is the alpha clamp a friction only clamp or does it somehow clamp on so it cannot move at all?
There is a small amount of fore to aft movement in all Troy Ind. sights. This does not affect zero and the amount of movement is controlled to ensure that this does not happen. The Alpha Rail uses contoured internal clamps that lock onto the barrel nut and teeth to eliminate movement. Thank you!