ATRS played with it for a bit
A few years ago I developed a cartridge I named the 300 Awesome, which was made by necking 338 Lapua IMPROVED down to 308 caliber.
I got 3600 FPS from the 240 gr SMKs. Not sure on what barrel life will be as I only have about 500 rounds through it to date, but I will be happy if I see 1500 before the barrel is done.
What the OP MAY?? be asking about is the new 300 Norma magnum I believe, not the 308 Norma mag which is entirely different again. The 300 Norma mag is simply a shortened 338 Lapua casings then necked down to 308 cal. The inventor Jimmie Sloan (6.5x47 Lapua amongst others) claims that the 230 gr Berger will get to near 3500 FPS and that barrel life is no worse than 300 Win Mag.
I am building 1 of these as well mostly as a lighter weight hunting rig, but as I just got my reamer last week have not had time to get to work on it.
OP The cost of casings and powder and custom dies is greater than the cost of the bullets. Also what is the point of lighter bullets? At extreme long range like these 2 grossly overbore 30 cals are designed for, 110 gr plinker bullets that ARE cheaper, just don't work.
If the plan is cheap buy a 22LR and fill yer boots.