No, not at all. Every hunter I talk to seems to think they need a 300 win mag, or 338 to kill an elk. I've shot 4 bulls and 2 cows with a .270. Dropped them where they stood. I just ordered a new 30.06 for this coming fall's hunt. But, only because it's a more versatile round as far as bullet weights go, and its half of what a box of 300 win costs.
I converted from a .300 mag to .270 WSM several years back, and have never been sorry. If you are a guy who plans to take the time and effort to become proficient killing elk at 600+ yards, you may want to opt for the .300. But for elk 400 yards and under, its hard to beat a screaming 140 gr accubond out of a .270 WSM.
If the price is right, Jump on it. One cannot have too many hunting rifles. Is a .300WM needed for Elk? Um... No. The .270WSM will do fine. A well built 140Gr or 150Gr Slug at a not to excessive velocity and you are good. There's not many critters on this continent that would truly NEED anything larger than that .270WSM. Maybe the Big bears (Coastal Grizzlies and the white ones...), and any Elephants that escape from the zoo... Short of that, any of the WSM's will be enough.
Well my unlce Fritz used to tell me that the only gun you ever really need is a 22 so keeping that in mind and having seen both a 270 and 300 do work in the brush id say spend that money on a good pair of boots. but this is being posted from a guy who shoots a 45-70. your call new gun never hurt my feelings
As a handloader, I love .300 mags because of the selection, but I'd be fine with .270 WSM too. Some guys only care to own one hunting rifle. Others like having dozens. It all comes down to your preference, but I don't think you will gain a noticeable amount with the .300.
I'll be taking a Remington 700 .270 & 30.06 as back up. Using my Winchester 70 XTR Sporter .338 as my main rifle. I think I'm covered with any one of these 3. I reload and all 3 will use the Barnes TSX. My wife buys shoes and clothes. I buy guns. There's no such thing as too many to me.