What I dont understand is that dont these soldiers already carry a couple of mags with themselves? I mean at least the special forces?
So instead of carrying 3 20 round mags why not carry 1 60 round mag?
There are some reasons behind that. The form is not very practical and is restricting the capability of the soldiers to shoot effectively from prone position which is very important.
For the fit yes it can be fit if needed but the weight is quite big. Aside the weight of the ammunition and the magazines on the vest also very important is the weight of the gun. If we imagine that the soldiers have to clean urban area which can take a lot of time and is very tough both physically and mentally then we realize that these soldiers have to use extensively different shooter ready positions like compressed ready, low ready/modified low ready and high ready positions. The lightest of these is the high ready position but it is recommended at least the poinman to move in low ready as it is faster to react from it and also it doesn't obstruct the vision of the second man behind (in a column formation) which is tasked to support and cover the same sector as the pointman.
Also apart from that it is often required to have an aim at the sector (without causing tunnel vision of course) which you are covering. All that requires very strong arms and shoulders with a normal 5.56 M4 rifle let alone one with 60 round magazine in it. One of the things that US soldiers still remember from their participation in urban warfare and especially in Falluja/Iraq is the strain on their shoulders from the ready positions.
As for the uses in Special Operations Forces it is a little bit different story. Apart from the Russian SOF many Western equivalents also start to use that concept more often. Our SOF units are also not strangers to the concept. One of the main tasks of our SAT Commandos (Navy SOF) is Visit, Board, Search & Seizure (VBSS) operations. These operations consist of storming maritime vessels. The boarding phase depending on the situation can happen by boarding by sea with a ladder attached to the ship or for example boarding from a helicopter. Both these methods require mobility to a very good extend in order the boarding phase to be completed successfully and safely. Then we have the storming phase which requires storming of the ship's different compartments. The ships can have very tight corridors, doors, tight stairs/ladders which require as much mobility as possible. In order to maintain fire superiority and if needed to open suppressive fire effectively our Navy SOF adopted PMAG 40 and 60 round magazines as replacement for Light Machine Guns (LMGs) in VBSS which will be to heavy, take to much space in that situation and also the reload procedure will be a pain in the a**.
You can see SAT doing VBSS training below
i like it, with longer and heavier barrel, the rifle can work as light machine gun.
www.thefirearmblog.com
