to me.
custom = choice of wood, layout, checkering, stock style, fit to shooter, choice of barrel, blueing type, action, mounts, rings, front and rear sights and zero height if express sights for various leaves with shooters main load. choice of bottom metal, engraving, flooplate, choice of jewelling/engraving/etc. choice of recoil pad, plate, steel, skeleton, leather covered, etc. etc. choice of finish on stock, usage of ebony/rosewood for tips, rounded tips, schnabel, etc. choice of free floating or fully bedded, choice of pillar bedding, glass bedding, choice of inlaid steel in forend to stop warping, choice of steel rod through wrist. choice of cross bolts and inlays used in screws. choice of sling studs and styles or barrel bands, choice of barrel twist, length, profile, etc. choice to have blueprinted, choice to have a different bolt handle or have it re-styled...list goes on, including triggers of course!
'that', is custom
Semi-custom = using existing components whether it's barrel, action or stock, and customising it by changing some or most of the 'other' parts/components, which could include any of the above.. however, mostly, when I hear of 'custom rifles', and all it is is a standard factor action with a new barrel screwed on, bedded into a synthetic stock, maybe with a piccy rail or a coat of spray paint...and with a price tag matching many true 'custom' rifles.
of course, there are many ways to 'semi-customize' a rifle, where do you draw the line, but usually the main component such as the action and maybe trigger + bottom metal is held constant.
Factory = mass produced junk with complete disregard to quality of wood, inletting accuracy, test shooting, etc. etc. only a few manufacturers make ' really good' factory rifles, of course, Sako being one, arguably Tikka is ok, but used to be great. There are others of course, but there is more junk than quality out there...............these guys (factory rifles) are the reason why aftermarket parts makers and synthetic stock makers, barrel plumbers and spray painters make a living