Two 300 WSM questions

[Uncle Alvah]

Recently I came across a statement regarding the 300 WSM in a custom built long range rifle. Specifically:

a 300 WSM tightneck shooting the 125 Grain B. Tip in a 15 twist at 4043 FPS.

I'm wonder if this is not significantly higher velocity than possible with a .300 Win Mag?

Also, I don't understand the term "tight neck"?

 

[dakotasin]

tight neck is getting into spec'ed out custom tubes and handloading beyond handloading 101.

the 300 win mag has more case capacity than the 300 wsm - thus, able to produce more velocity. i've never run 125 grain bullets in either my win mag or wsm, but in every other bullet weight i've used, the 300 win mag gets more velocity.

the 300 wsm is a fun cartridge.
the 300 win mag is a fun cartridge. i've used 'em both extensively for handloading, hunting, and targets at distance.

 

[aspade]

That's a full 500fps ahead of published loads.