. Ordered a McGowan 20" barrel for the 457, hopefully it's a fricken lazer.
I'm not familiar with McGowan, but having experience with Lilja and Shilen barrels, rimfire rifles are still not lazer beams, no matter how good the barrel. Even with a great barrel blank, the littlest things a smith gets wrong in fitting can turn it into nothing more than an average shooter. Say all goes well with a good blank expertly fitted and finished, the hunt for good lots of ammo to feed it can make you pull your hair out. I produce some excellent results from time to time with my 455 custom/Lilja, though I would say on average it shoots groups at 50 yards in a (non symmetrical) bell curve centered around 0.3".
I rarely see groups in the 0.5's +, likewise 0.0's are elusive. A handful of 0.1's tend to pop-up during an extended range day. Many 0.2's and 0.3's, some 0.4's. Although this is ostensibly excellent accuracy for a rimfire (perhaps "lazer-like to some), it is still a notch back from the cutting edge of where rimfire accuracy is at today. I cannot stress strongly enough how difficult it is, from a manufacturing/gunsmithing perspective, to construct a barrel, put it together with an action, bed it in a stock and end up with something
capable of peak rimfire accuracy,
if one manages to acquire some ammo that doesn't suck. Now, go set out your wind flags and shoot the thing
Results as I've described with my 455 custom are realistic if one has an excellent example of a factory gun such as an Anschütz, or does a good job building a CZ custom (not limited to these brands, just a ready example). To go above and beyond, strap on your parachute and jump into the rimfire rabbit hole.