Re: .223 to a 6x45?
You're going from .223 Rem. which is a 22 cal., to 6x45mm, which is a 6mm. You need a 6mm barrel, which needs to be chambered for the 6mmX45mm cartridge. A 1 in 12 twist will shoot 75g.-80g. bullets @ around 2800fps. A very 'forgiving' and easy round to load for. Cases are made by full length sizing new .223 brass with a 6 x 45 sizing die, one pass will do it. Normally, there are no major magazine/feed issues.
"Shoots real good!": definition; it didn't blow-up in my face. Not everything can be fixed on an internet forum!