Re: I need to push a 180g 30cal over 4000fps what are my options
I've never read of muzzle velocities reported near 4000 fps with a 180 gr .308 bullet. Of all the members of this Forum, Kirby comes to mind as the best source for the lowdown on such an ambition. I'd send him a PM.
To my knowledge, Kirby never marketed a .300 Allen Magnum. He jumped from his 7mm Allen Mag up to the 338 Allen Mag. IIRC, he wasn't able to design or conceive of a practical 300 Allen Mag that substantially improved upon the 300 RUM.
My guess is that 4000 fps with a 180gr .308 will not become a reality with any shoulder-fired weapon that's practical for hunting, at least with the use of brass casings. The college effort might involve the use of casings with screw on steel case heads that allow much higher pressures to be employed without blowing gases out around the primer pocket. The first point of failure would likely then be from the equivalent of a pierced primer. I knew of a guy about 20 yrs ago that was having steel case heads custom built for his .338-.378 Wthby Magnum. He was able to run the case pressures substantially higher than with brass casings. The overall casing length was increased from the standard brass casing, and each custom manufactured casing was very expensive. He had to have a custom reamer built for the elongated cartridge case. The steel case head more or less screwed onto the meaty portion of the .378 Weatherby case heads. This guy was a doctor with plenty of money to burn. I don't know the details on the velocities he was getting. My information was 2nd hand from my brother who's a local gunsmith and gunshop owner. I think the effort was rather short lived, because I only heard about these steel case heads for about a 1-2 year time period. There were probably some safety and cost-effectiveness issues that brought the experimentation to an end.
At the elevated pressures, barrel life would likely be significantly reduced.