I'd jus pick up a TC Venture for around $400 as it will cost about as much as the barrel in the long run. I had a Venture .270 for a short time and it was a shooter. I bought it for $400 out the door, TC was giving a $50 mail in rebate so the rifle cost me $350. I put a 4-12X40 Revolution on top of it for $175. Sold it to a former coworker for $525 when I was done playing with it, and he loves it.
I just didn't need three rifles in .270 Win and that is why it went down the road. It shot cheap Remington 150 grain Core-Lokt about an 1.25" for five shots, and Federal Premium 130 grain TTSX loads well under 1" for five at 100 yards. Unless you get a smoking deal on the Encore barrel I'd just buy a whole new rifle.
I have an Encore with .204 Ruger and .300 AAC as well and would love a ML barrel for it, but the whole switch barrel novelty wore off really fast for me. My buddy from NY got me interested in them, but with his laws the Encore makes sense as he can have as many barrels as he wants without having to register them like he does a rifle or pistol. For me while CO has become a bit of a PITA it isn't anything like NY and I'll still pick up a new or used rifle in a common cartridge like the .270 Win. I usually don't purchase anything but a specialty or wildcat cartridge chambered barrel for an Encore and I traded for the .204.