I remember when I made the jump from shooting bolt action rifles as a kid to shooting my first AK style rifle.  Besides thinking it was cool and fun to shoot, I realize that the kind of felt awkward to shoot from the table.   The real reason was that my size didn’t really support the gun very well and it was the protruding 30rd magazine that made me sight a little higher than I wanted to.  I later picked up a Yugoslavian SKS rifle and even though it fired the exact same 7.62×39 round, it was far more comfortable to shoot, and it was easier to lay lower on the ground.    With my present level of training I realise there are shooting positions that you can move into and still remain low to the ground, but still not always practical.

Another simliar comparison would be for an AR 15 style rifle vs a Mini  14 with a 5rd magazine.  The next time you buy a gun and are looking to stock up on gun magazines, pickup a smaller capacity magazine for table shooting and see what I mean. These differences really come out when taking a firearm on a long hunting trip, because finding a good firing position is extremely important to getting a good hit.    I have a few 10rd magazines for my M1A rifle that I like to use when shooting off of tables.   Even though the gun is normally sold or issued with a 20rd, the smaller capacity helps keep you low and gives you a little bit more potential for movement.