Here's a photo of the 457 American that I just re-barreled with a Shilen select match ratchet rifled #5 blank. I'd considered threading the action, but decided instead to glue the bbl in - if it doesn't work out, I can always clean up the Loctite #609 & thread it later. But - at least so far - it appears to be working out. I finished the blank by cutting the extractor grooves & made the cut on the bottom of the shank for the feed tray to fit into, then de-greased, blasted, & CeraKoted the bbl & muzzle thread protector with a mix of 20ml of graphite blank and 10 ml of tungsten. The nitride finish of the 457 appears to have a slightly blue/black tone, and I thought the mix might come close to matching it. The Shilen - as I contoured it - is just over 1/2lb heavier than the OEM American bbl, even though it's an inch shorter at 23".
I had a hurried prone session with it from 50yds yesterday morning while the breeze was still fairly light, and after getting a rough zero on steel, shot some groups on paper. The one I attached is the 1st 5-shot group on paper, with SK Std+. The first four shots were touching, but I saw a weird recoil track though the scope on that fifth shot that landed on the black paster. Not terrific, unless you'd seen how the factory barrel was shooting - then it looks pretty good by comparison. I shot some 10-shot groups with SK LR Match, Flatnose Basic, Pistol Match, and Lapua Center-X; LR Match & Flatnose basic had six or seven shots all in one little hole, with the remaining 3-4 shots within 1/4". In short, it shows good promise. Afterwards, when I checked to see if the bbl was still free floated in the bbl channel, I found some contact in the last 4" or so of the forend, so a bit of sanding to remove that might just tighten up the groups. I've got to remove the bbl'd action to engrave the chamber on the bbl anyway, and to seal the sanded bbl channel with some urethane varnish; might as well get that done while it's still raining.
So this is the first Shilen bbl I've ever worked with - if it continues shooting the way the initial trials indicate, it won't be the last...