What a bizzare coincidence that your getting a 300WSM barrel. Maybe you can stop the order if it's not delivered yet?
I was recently at a shoiting range with a friend who is a member there. While I was watching 4 guys shoot their encores and contenders two of the fellas were angry about something, not fighing with each other but rather just stressed about their guns. With head phones and ear plugs it was hard to hear them.
During target change outs I was talking to a third guy in the group and he said that they were both disspointed in their 300WSM barrels and handloads. One also has a 308 barrel and was getting the same performance from the 308 as the 300WSM. We spoke a bit until the 300WSM guy came back and he said it's true that the 308 matches the barrel length so well that the 300WSM cannot improve performace with that shorter barrel over what the 308 was doing. Plus the recoil was much less and the gun more accurate in general.
I'm not knowledgable of this from personal experience but it stands to reason that bigger case would struggle in a short tube where a simple 308 loaded properly in the same length would likly be far more efficient. Something to think about anyway.
Oh One other thing to mention, he also had a 308 necked up to 338 and that thing was sweet. It had very low muzzle blast, it was one of the quietest discharge sounds I have ever experienced with a centerfire gun. It was also very accurate and he was shooting at the 200 yard targets.
I don't recall the velocity but remember thinking it was a surprisingly good at the time he said it.
