WSM SAUM heavies out of short or long action

Currently considering a 300WSM, 7-270WSM or 7mm SAUM to shoot either the 210gr 308 or 175gr 284 bullets and heavier. Long or short actions and why? Anyone running these out of mags and if so what mags? What should I look out for?

PS any for sale?

Mines not heavy but throws 150g bergers (7mm saum ) out of an 18" barrel at 3043fps. Short action rem700, don't find anything to bag it down. But possibly if I wanted to shoot a larger projectile with a longer seat, my mag wouldn't hold it. ( lucky 13 8 rd mag ).

300 saum. 20". 168 grn NBT @ 3K.

Short action A7, converted from 270wsm.

Efficient and effective.

I'm running a 7SAUM on a Rem700 longaction. Was using 180 VLD's. Using AI AICS .338 Lapua CIP mags. Plently of room left in the mag.

Easiest option:
Start with a factory tikka 300 wsm. You can get mags tweaked to accept the case with bullet seated further out.
You will just need a longer bolt stop . If you don't like the .30 cal you can change the barrel to a 7 blaser, 7-300 wsm or a 7 saum and sell the barrel for 200 to 250$ and you still have a good base to start with .

Other option :
A Remington short action in 300 wsm will need alteration to the underside of the action and an internal mag extension to gain a few mm to seat your bullet further . Otherwise you go long action.
If you go custom, defiance makes an action intermediate between short and long but prepare to be very very patient.

I've never had any of the short mags however I've had plenty of time with the old man's Sako a7 300wm. Having experienced the restrictions on cartridge length the relatively short magazine allows I'd advise you to go for at least a medium length action. If you do decide to go with a short action I'd pay careful attention to the throat length and match it with the magazine length.

These cartridges were really designed to match long action cartridge speeds in a short action with the typical shorter, lightish soft points in most factory ammo. Put long pointy bullets in them and they don't fit that well in the short actions.

If you're considering the 7-270wsm then you should also consider the 7-300wsm.

If you decide on using a long action, then I'd go for the 7mm Blaser Magnum.