S&F,
Haven't I told you before ... all Rem 'standard' length actions are in reality H&H magnum length. A Rem700 chambered to 30/06 actually has a magnum length action which will take a 375H&H as long as you open the bolt face, replace the magazine box, follower etc... and open the rails. That is do all the work necessary to get it to what a stock Rem in 375H&H has.

A Rem700 in 300WinMag will need the magazine box spacer taken out, longer follower, maybe some rail tweaking and it's pretty good to go for a 375H&H length cartridge. I have a sneaking suspicion the Vanguard/Howa's are similar.

I think what causes confusion is the word 'magnum', in it's traditional sense a 'magnum' action was H&H length (or longer) ... where say a Ruger MkII 'magnum' action (not the RSM its a true magnum length action) is in reality a standard length action with magnum bolt face and limited to 3.3" COL. Then we have 'short magnums' which are really just short actions with a magnum bolt face and limited to upto about 3.1" COL and often much shorter.
Cheers...
Con