Attached Link: Aliens Smartgun

To add a figure using the rifle:

• Add M4 to your scene.
• With M4 selected, apply the pose file (SmartgunM4) to him and he will be placed in the correct stance.
• With the smartgun selected, apply the pose file (Smartgun) to the Smartgun and it will be placed in his hands.
• Turn on IK for both arms for M4.
• Select the left hand of M4. Go to Object > Change Parent and select LeftHandle on the Smartgun.
• Select the right hand and repeat, parenting to RightHandle on the Smartgun.

Now when you animate or move parts of the Smartgun, he will move with the movements.

Quote - The Marines` Smartgun from the Alien movies. In the movie the smart guns carried by Vasquez and Drake were based on the German MG-42 machine gun.

Then why did they look like US Army M-60's?

That's because the M-60 is loosely-based off of the MG-42 design (as per "Lock And Load with R. Lee Ermey").  In fact, the only thing the U.S. military did was lower the rate-of-fire (to help keep barrel changes down- the 42 was notorious for making barrels almost white-hot due to its incredibly high rate-of-fire) as well as some other cosmetic (and not-quite-so cosmetic) changes meant for a modern battlefield. 

The M-60 may very well be based on the MG-42 but the "smart gun" heavy MG operating end looked just like an M-60. I used to carry one, trust me I know what an M-60 looks like. I suppose it's possible that for cannonical reasons it gets said that they are based on the MG-42 but the props in the movie look more like a modified M-60.

Interesting how this free prop looks more like an MG-42 and the movie props look more like an M-60.

"The actual weapon is a modified German MG34 machine gun.  (You can see this gun in Saving Private Ryan, in use by the German troops)  Most of the added "acessories" are actually bicycle parts, including grips, a brake lever, and front suspension.  The weapon is stabilized using a steady-cam harness.  Steady-cams are used by filmakers to keep the camera from moving while the camera operator walks along."

and from another site:

"The prop was created using a modified 2nd World War German MG-42 machine gun. The “trigger” is a Kawasaki GT motorcycle brake lever, the front barrel dressing is derived from a motorcycle foot rest and the grips are Kawasaki GT switch gears. The muzzle brake (the very tip of the gun) was specially made to alter the look of the barrel and adds to the overall detail and to create a unique looking weapon."

And the image is supposedly the official technical drawing of the movie version.

I need to watch Aliens again. Excellent work on the prop btw, now if I could just find my predator character again. (there was once one in the freestuff, many years ago).

"And the image is supposedly the official technical drawing of the movie version."

that is from the ALIENS Colonial Marines Technical Manual ( http://www.amazon.com/Aliens-Colonial-Marines-Technical-Manual/dp/0061053430 )

fantastic model! Thanks for sharing it :)