030370, I have a 7 STW and I love it. I think the 7mm RUM is not an efficient case when the two are compared.
I would go with the 7 STW and 156 Cauterucio bullets. Bob Cauterucio makes some great bullets. BC is .615 he also makes a 176 with a bc of .750, but they a very long and require a 7 or 8 twist. The 156 would require a 9 twist which is better if you use other bullets. My STW has a 26" krieger and loves the 156 cauterucios.
The WSM's are great and if I were building a rifle I'd go with the 300 WSM
. I konw you like the 7mm but the 300 WSM is such a great caliber. Great bullet selection and ballistics with the 300 WSM!
As far as barrels go I love my krieger, but I just built a 338 lapua with a lilja, and I must say the lilja is unbelievable! With the WSM I'd go with a 28" barrel. I know others like longer barrels, I find diminishing returns past 28"....just my opinion.