The 308 Norma is a great round & anyone that has this round in a good rifle is well equipped indeed. It is very accurate but there is no evidence that it will outgroup a 300WM. The old gunwriters did a heck of a job promoting the idea that the longer necks were crucial
to get the best accuracy & I like the long necks too, but the facts did not support their case very well. Both the 308 Norma & 300WM & even the 300Wea. won their share of 1,000 yard matches, but the 300WM won more than the other 2. And this trend started before the 300WM was very popular, the Wea. was but the 300WM 308 Norma were not yet, but the 300WM has elisped the other
2, on the target range & off, good marketing could cause more sales to the hunter, but performance rules on the target range. Also, look at the sniper/Mil. rifles in 300WM, if the 308Nor. had been measurably more accurate, that would be a known factor, which it isn't.
Sometimes a cartridge is known to outgroup others. A case in point is the 22PPC-USA. The 222 was king for years, but the PPC took it's spot long ago & the PPC has a shorter neck, hmmm.
If you ask Kenny Jarret or Charlie Sisk or a host of others which magnum round gives the best chance of inherent accuracy & many will mention the 300WM first & others second & the 308 Norma will not be mentioned in most cases at all. Also, if a longer neck alone would give better accuracy across the board, then why does the 300Wea. not outclass the 300WM, even when you chamber the 300Wea. without the excessive freebore?
As far as the Norma being just as fast as the 300WM, it is almost as fast with bullets of 165gr. & under, but not quite. The 300WM pulls
away a little more with 180gr & more so with the heavies. In a std. length magazine like a Ruger, they can run close, but in a long magazine rifle like a Rem 700 properly chambered, the 300WM will win every time due to simply having more capacity. My 300WM Sendero is so chambered & a 308 Norma would have trouble getting within 100fps of this rifle with equal pressures, the same way that a 300Wea. set up the same way will get 75-100fps more with 180's & above than my 300WM, just a matter of capacity.
The 308 Norma is great in it's own right & doesn't have to compare with a 300WM in velocity & they are very accurate, but to think you will buy one & it will offer a measurable difference in accuracy compared to a 300WM is unfounded. I have no desire to have a pi##@@&& contest here, but rather to look at it from a practical standpoint without unreasonable expectations for any round.
But if your goal is 3,000fps & change with the 180, you have the right cartridge & it really is a fine round.
Good luck