Welcome to the forum. OK, mag in, no ammo, pull back on the charging handle, release and then pull the trigger? With an empty mag inserted it should have locked the bolt in the open position, and it will not fire in that condition. The bolt has to be forward or in battery to fire.
I just bought a Troy 11" TRX for my AR, and I tried to install it on my Colt M4 Ops first, but it doesn't fit the Colt/Umarex threads. So I am assuming at this point that no AR hand guard will fit the Colt/Umarex. I suppose that some enterprising person could fabricate a thread adapter that would do the job.....If you come up with something please let us know!
A range trip sounds like fun, but that would be a long trip. FYI, I am a satisfied M-4 owner, got one about 3 years ago. My observation has to do with the profligate use of zinc alloys, or Zamak in it's construction. Also with the extensive dis-assembly required to perform a thorough cleaning. Walther's procedure is inadequate in my opinion. I also have noticed a drop in Walther's quality when I look at my PK380 - while I really like the gun, and I use it for EDC, it doesn't really seem like normal German engineering. Just my 2 Pfennigs worth.
The 416 looks nice, I would like to handle one. Thanks for posting the catalogs cdnite! I understand what MG is saying - these guns may be a bit too close to air soft quality......but they sure do look like fun!
It is not free, but go here http://www.military-manuals.com/military_vehicles_manuals/m35-6x6-2-5-ton-military-truck/m35a1_m35a2_military_truck_manuals_p1.html for the manual, it's $30... And don't forget the Idaho Motor Pool. http://p8.hostingprod.com/@idahomotorpool.com/index.html ;D