(adsbygoogle = window.adsbygoogle || []).push({}); Make two classes with the following:
(You will need Bling!)

1st Class:
Assault Rifle with:
Extended Mag
ANYTHING

2nd Class:
Same Assault Rifle with:
ANYTHING
ANYTHING

Steps:
1- Kill your self using the gun with extended mags
2- Switch classes to the 2nd class and pick-up the gun while holding your secondary
3- Switch to the gun that does not have extended mags and shoot

Example of a gun to test this out with:

1st Class:
M4 w/
Extended Mags
Red Dot

2nd Class
M4 w/
Red Dot
Noob Toob

Now you should have the following in one gun:
Red Dot + Noob Toob + Extended Mags!

Credits to IV for tut.

I'm going to try it out

Thanks for all the positive feedback guys.

Pretty cool, maybe it was intentional? Because realistically you could pick up a few extra mags on the battlefield, but it would take to much time to take off a scope from another gun, or FMJ.