The USMC is the only branch of the service that switched to the M60e3, the SEALS use a version refered to as the car60. Both the car60 and M60e3 both have a forward pistol grip, frame mounted bi-pods, and quick change barrels, however the car60's barrel is aprox. 6 inches shorter than that of the e3(the barrel is equal in length to the end of the gas system). The M240G/B or similar in size and wieght to that of the Army version of the M60(never got the appropriate model designation). The M240 is a much improved weapon system over the M60; more reiable, greater accuracy, longer max. effective range. Feed tray design, gas and operating system , barrel length, and cradle all lead to this.
To keep it simple machine guns(M60/m240) have many roles, the least prefered offensive method of deployment is assualt fire; ie. shoulder, hip, or thigh. The most disirable is supporting troops by covering movement and softening targets at max effective range and preferablly in a partial/defilade position(so your machine gunners are protected).
The SEALS are using a weapon system that they feel suits thier needs, which are different from the rest of the military. If i was a grunt on the ground needing cover fire going into the offense or sitting in the defense firing a FPF I would take a Marine Lcpl. with a M240 than a salty SEAL with a chopped M60 to cover my back anyday.
Im not sure if the Army has made any changes recently in the way they pick machine gunners but they have it all wrong. The person who carries the pig shouldn't be the new guy, boot, wanna be rambo etc. The should be full time gunners that are trained fully in the use of thier weapon system.
I loved the fickle M60e3 as well but , the M240 is hands down a better system.
Sorry for the spelling, spell check is down and im not looking this up in the dictionary today.
RUGGER