The dealer must have been talking about the 7mm Ultra Mag, NOT the WSM. The Ultra Mag I was reading about in a recent hunting mag. and they stated, with the 140g. bullet you could be sigted in around 2.5" high at 100 yards and have an effective kill range (within 6" circle) out to near 400 yards. I think it' s pushing the bullet around 3,400 fps...lemme go check my Nosler book...
Ok, here' s the deal. If you are shooting 140g. Balistic Tip at 3,400 fps and you sight in for a 300 yard zero you will be 2.6" high at 100 yards, 3.2" high at 200, and 7.4" low at 400.
Here' s some good info;
http://www.chuckhawks.com/7mmRem_Ultra_Mag.htm
He has a great site that is referenced here often including info about all the WSM cartridges. Or just do a search on Google.com like I did to find that site and there is lots of info.