kombatkyle,
I have a couple things to offer. In the interest of harmony, what follows is my OPINION based on MY experience (I tend to wax hyperbolic occasionally) and I do not mean it to sound haughty, even if it does.
1. First of all, putting good barrel on an old receiver (As others have said) is kind of shooting yourself in the foot. The receiver is foundational to the performance of any barrel. Also has been stated, the V block is Old Tech.
2. I shoot mostly precision 22lr and I get excellent groups out of my stock CZ 457 Varmint (granted it is sitting in an extremely good MDT Chassis, also made in Canada) with a variety of match ammo but i ALWAY, ALWAYS, ALWAYS allow the barrel to get used to the lube on the new ammo before I ever track a group. These are known as Fouling rounds and are super important. The only exceptions to this are SK and Lapua (both made by Lapua) use the same lube and in my experience, very little is required to switch to RWS as well as I think their lube is similar. Some of the rounds you may have shot might have had copper jackets which for me, is a huge no no in my rimfire guns as it results in copper fouling which is bad enough in large bore rifles but takes a long time and a lot of rounds to clear out of a 22. I never shoot copper in my guns, EVER! Apart from a firmly mounted barrel, the most important thing in accuracy (remember that accuracy equals repeatability) is consistent loads and in match ammo, what you pay for is QUALITY CONTROL. brass, Lead, and powder are all priced much the same. Even a coupe grains of powder make up a much larger percentage of a 22 load than they do in a 308 for example so it really counts.
For practice and plinking, I am currently working through a few bricks of RWS Target Rifle which shoots 1 hole groups at 50 all day, well under an inch at 100, and I can somewhat reliably shoot groups under 5" at 300 yards (better when I get a good wind read). It's not as good as Eley Match or RWS 50 or Lapua Center X but it is a LOT cheaper and readily available at tenda, tesro, etc..
All but the Eley you mentioned would never ever be put into one of my guns. CCI makes a good semi-auto pistol round in my experience but I would never hope to shoot groups. Remington make a nice shotgun and a great platform in centre-fire rifles but their ammo is garbage IMO, likewise Winchester. Match ammo only please. If it comes loose in a box of 300 or more, it's not good ammo and you can't expect it to group. The exception to this is SK Magazine which is hard to find dammit. I think Eley might also do loose bulk ammo. So OK, if it's Match ammo and it's loose..........lol
3. Finally and IMPORTANTLY for this thread, I have to give a huge Shout Out to the folks at Grey Birch who have provided me with much higher customer service than I could have expected or, frankly, deserved. They completely looked after me when it was me who messed up. By today's or any standard, I am super impressed. It has been a long time since I have experienced customer care like that. I am absolutely thrilled with my Fusion 16.1 and I eagerly await my fusion RDR (12.5") which I ordered just in time back in May.