If you already have a lap, no harm in lapping them. However, if you don't already own one, no point in buying one unless you're a high end competitive shooter. Seekins rings should be good to go.

The front attachment point just uses the Sako brake, factory part #S5740412. The mirage strap itself is #S2501858. I haven't found any info on an adjustable cheek riser.

The barrel on my 20″ CTR tapers from 1.2″ at the action to .83″ at the muzzle. I'd assume the 24″ would have a similar contour.

You can use any barrel you wish, it will just need to be profiled, chambered and finished by a competent gunsmith, pretty much like most bolt action rifles.

I have a RZR Gen II on my CTR and cheek weld is fine, your face might be different from mine so you should always expect to make some adjustments to the cheek piece, scope mounts and rings. I… Read more

You can put on any barrel you want really, it will just need to be threaded, profiled and chambered by a gunsmith. It's also worth noting the factory barrels are torqued on by a gorilla. Even if a pre-threaded, short chambered barrel was out there, you'd still need proper tools to get the barrel off, or a lathe to cut it off.