The Engagement Skills Trainer 2000 (EST ) uses Bushmaster weapons that have been modified to function off of air instead of ammo. Of the un-modified standard Bushmaster parts, the following have the highest rate of failure:
Hammer/trigger pins (shear in half at the groove(s). USGI never do this).
Bolt catch (breaks at the oval thumb pad if laid down hard with BC locked to rear,
USGI never do this).
Plastic
trigger guard (duh!) breaks.
Charging handle loses pin.
Rear sight housing is shaky (spring at ball is weak).
Disconnector wears fast (results in double-fire)
Trigger sear step wears fast (weak steel/heat treatment)
If you do buy a Bushmasher, replace the above with USGI parts and you'll be OK.
45K40
Threaded Mode
