Per what I have been told previously by my gun building buddies is also stated below--as it points out, think the idea is much less about actual weight and more concerned with accuracy..every little bit helps .. kinda like packing for a 2 week backpacking trip...cutting off the handles on the tooth brush.(for those of us who still have teeth

, ounces make pounds.. every little advantage to win the match, etc...

This is a brief article I found..

The short action receiver (built to hold .308 Rem/NATO length and shorter cartridges) is typically about 1” shorter and weighs about a quarter pound less than the long action receiver. Its shorter bolt throw could theoretically allow slightly faster reloading. Since it has a much shorter ejection port, it is stiffer and will not torque or bend quite as much as a long action. It also has a lighter firing pin in most rifles so the lock time (the time from pulling the trigger until the firing pin hits the primer) can be (and on the Rem 700 IS) faster.

The last two differences make the short action popular with benchrest shooters because they need everything they can get for accuracy and they typically don’t need powerful cartridges to punch a hole in paper. The short lock time helps them get the shot off while they see the cross hairs exactly on the target. Nowadays, we have good action bedding systems so that neither the long or short actions are allowed to bend or torque so some long range benchrest shooters use long action cartridges very effectively. Custom aluminum firing pins are also now available to reduce the long action lock time to nearly the same as short actions.
The long action receiver is built for 30-06 and shorter cartridges. Therefore, you can shoot a .308 Rem cartridge and even shorter cartridges in them too if you like as long as your barrel is chambered for the cartridge. Both the .308 Rem (short case) and the 30-06 (long case) shoot 30 caliber (.308” diameter) bullets so you seldom see someone shooting .308 Rem cartridges in a long action. They typically just use a 30-06 cartridge version. Both the 30-06 and the .270 are "long" cartridges so they won’t fit in a short action receiver. People typically use long action receivers to enable them to use more powerful cartridges.