what is the differnce between 7mm rem sa Ultra or 7mm stw or 7mm wsm.
i have a 7mm rem mag. are the ballstics close to the same

The 7mm STW has a greater case capacity and will be faster than the other 3. The others are pretty similar.

Taking a 140 grain bullet, and comparatively close burning rate powders, we find:

7mm Rem Mag - XMR3100, 68.0 gr @ 3083 fps
7mm Weatherby Mag - XMR3100, 70.0 gr @ 3176 fps
7mm WSM - XMR3100, 69.5 gr @ 3181 fps
7mm SA UM - MAGPRO, 70.0 gr @3197 fps
7mm STW - MAGPRO, 79.0 gr @ 3209 fps
7mm RUM - XMR3100, 85.5 gr @3428 fps

All data referenced from the Lyman 48th edition reloading manual. Wish they would list the same powders for all cartridges, but with all available, probably not practical.

7mm Rem Ultra Mag(RUM) is a super magnum cartridge which in turn is remingtons flattest shooting Ultra magnum. Barrel life however is low if you would like to do follow up shots im sure in less then 600 your barrel is dead. Its ballistics are amazing 7mm STW and WSM need not even be mentioned against the monster the weatherby's are the only cartridges I know to even compare to its power although accuracy is limited to the shooter for reason of tolerance to recoil and rifle care.

Let it cool after each shot and take good care of it hopefully it will last longer then 600 rounds. It and the 300RUM, 30-378 weatherby, 257 weatherby, 300 weatherby are all monsters in a league of their own and so is the cost 35-100 bux a box for the weatherby's same with the Ultra magnums. Performance isnt cheap Id perfer to stick with the lower class magnums winchester and what not wont break the bank and still provide meat after each kill rather then vaporizing the animal and you can pick the bullets up at your local walmart!

Stick with the 7mm Remington Magnum ammo everywhere low cost and your barrel will last longer.

The 7 Mag is still a good one... I wouldn't get rid of it in favor of an even more overbore capacity cartridge. But a lot of guys have/will. If it's a matter of which toy is more fun then the hotter, faster ones might win out but from a practical standpoint it probably doesn't matter most of the time.

Incidentally, the extra velocity of these newer hyper velocity rounds is most useful for shooting at ranges that most people shouldn't be attempting on game. And I believe most of them come with 26" barrels too. If you sit on a stand all day long then it won't matter. If you want to actually walk around in the woods the extra 2" might be a handicap.