Well i think i have a change of plans. Originally i was thinking of building a rifle in a saum. But the action came in and looks like its an undesignated action. So im really considering building a rear grip sp! How would i go about doing this? Ive been drooling over some of the pistols here for a while and had no luck finding a cheaper xp to build off of so this may be my best bet! I want to build it for long range hunting and target shooting and really thinking of one of the short mags. Guys got some ideas where to start? Thanks guys!
I'm not really sure what you're asking. You didn't say what make/model action you bought. You didn't state exactly what was marked on the 4473. You didn't state your age or what state you live and want to hunt in.
Read the 1992 Supreme court case of the US vs Thompson Center. It outlines how your choice of barrel length, stock selection, the owners age and federal laws interact. It's not easy reading, but my understanding is if you bought it as an "other" receiver on the 4473 and you're 21 you can assemble it as a pistol and use it as a pistol or rifle as long as you obey the 16" barrel / 26" overall length when it has a shoulder stock. You can only sell it to someone 21 or older. I'm not a lawyer.
You're state laws determine what you can use for hunting.
I would assemble it with a barrel over 16 and with a pistol grip and a detachable (or interchangeable) shoulder stock. Then I could use it as a pistol or a rifle without it being an SBR. I have a few firearms like that.
A SAUM boltface can be used with SAUM, WSSM WSM, and some belted mag cartridges. I'm assuming it's a short action. What is the magazine length? In a short action you can shoot lower drag bullets with WSSM series of cartridges which have similar case capacity to a 308 Win. At least consider them in your selection. Muzzle energy will of course be higher with the SAUM or WSM cartrdidges. Consider the ballistics of whatever bullets and whatever cartridge will fit in the magazine including muzzle blast and recoil in your decision. There are lots of choices.
Then you have to get a barrel made with decisions on length, weight, contour and chamber to match the cartridige and bullet's you choose. Then you have to come up with a stock ( find one, have a custom made, or do it yourself), and decide on suitable sights or scope.
It's lot of time, work, and cost. Maybe even worth the effort,