With custom barrels, you have a greater likelihood that you will be buying a barrel that has a greater potential for accurcay..i say "potential" because i have had some factory barrels that shoot as well as my customs; unfortunately i have had some factory barrels that were pretty lousy...
I have about a dozen customs barrels at the moment, and have had twice that many over the years. I have yet to get a custom barrel that i could find any fault in, but it does happen...I will say that my barrels from Bullberry, SSK, and Virgin Valley are more consistently accurate with a wider range of loads; in other words they seem to shoot not just one load well, but are more tolerant with a wide range of loads / powder combinations. Another plus, if you shoot a lot, is that barrels by SSK & Bullberry are less prone to powder & copper fouling.
Are they worth spending a hundred bucks more? Well, sorta depends i guess, i personally would probably not spend a $100 more to get a barrel that i am going to casually plink with, but if you were going to do some serious long range varminting &/or competitive shooting, then a hundred bucks seems well spent to me.
I have a 21" 7TCU in a factory carbine, an early production barrel i got from another Graybeard member..it shoots very well for what i plan to do with it, which is to shoot small deer under a hundred yards. It holds about 1.5" inches pretty consistently. I cant personally tell much difference between a deer gun that shoots a 1.5" group or one that shoots a half-inch group when i am hunting, so it wouldnt have been worth it to me to spend another hundred on a custom barrel that might shoot a 1/2" group..either way, the deer is coming home with me! :wink:
the 120 grain Sierra's or the 120 Hornady SSSP will be fine.