I believe the 458 Socom has a top end a bit higher then the trap door but lower than the marlin loads.
The SOCOM (to date) has not been SAAMI spec'd or tested for pressure.
The limiting factor (beyond timing issues with certain powders) is the bolt.
In order to accept the rim of the cartridge a standard .223/5.56 bolt is used but "opened up" a bit at the bolt face.
This...of course, weakens the bolt somewhat and the unofficial "safe" limit is thought to be about 35,000 psi, although one German testing firm subscribes to 44,000 psi.
Those of us who reload for it...use the lower figure and have experienced no problems.
Hope that helps,