In addition to what Ronnie said...
ammo that shoots great at 25 yards may, or may not, perform the same at 50 and 100. Until you start spending serious cash on match ammo you won't see precision. Even match ammo will have mean velocity variance large enough to open a group up at 100.
If you're going to pillar your action, then bed it at the same time. You can add barrel shims later to test if that makes an improvemment, and then decide if you want to full length bed it.
I want to caution you again about the rimfire rabbit hole...especially with a ~$450 sporter.
