The M249 SAW actually has a magazine well to take M-16 Mags if needed. It was allways highly discouraged though unless your mags were brand new.
actually your saw has a fire adjustment on the front (rate of fire)
http://www.armystudyguide.com/m249/studyguide.htmIf its cranked up (when belt fed-box it should be unless your armorer is slack) yes the clip feed doesn't feed the rounds fast enough into the chamber and you will get a misfire then have to clear the jam and re charge it.., a brand new clip may solve this but just crank the rof down.. problem solved..
Also I see alot of people wondering why you tap the clip.. one is dirt and grime.. the same holes in your web gear that keep all that nice rain water out of your magazine holders also lets dirt and grime into your web gear to foul up your magazines.. the other reason is to enshure that the ball ammo in your clip is uniform and aligned. (sometimes the ammo is not flush against the back of the clip.. the firing pin misses or barely contacts resulting in a misfire) (as gunslinger said especially if your firing blanks since they are short) (him being at the mojave (op4 jackal) has experience with this.)
This keeps the m16 happy and when i have done these things i have had no jams..(imo clip maintenence is more important than bolt cleaning, ive had bolts straight black with grime and still fire, but one bad mag{either worn spring, or dirt} and the weapon misfires every damn time..) (granted some of the military weapons are POS with 10,000+ rounds and little armorer oversight and those weapons have many problems compared to something right out of the box.. so all your clip techniques wouldn't matter anyway.. and yes i had to trade one of those pos's ( i think it was a old a1) in korea out becuase it was so fubar...
m16 is great weapon does what its supposed to do {be light, interchangeable,more ammo per weight, durable,women handling it etc} but it does have some nuances.. (im a fan of the AK47 fire and forget, maintenance, what maintenance)
the clip maintenence being one of them..
DoctorYo