M/c
I have several hundred rounds of Kynoch .280, (after 60 years of collecting and shooting Rosses of all stripes) and I will tell you that virtually all will split their neck when fired, so they are a one time effort.
They are OK as display items, or a as companion piece to a real .280 sporter, but they are "consumables" if used.
Also, anyone shooting them MUST (read MMUUSSTT) "boil out the barrel" (run boiling hot water (ya ya I know about ammonia soaked rags) through the barrel, using a specially shaped funnel), as the primer are mercuric and (salt) corrosive (that's why most Ross barrels are "stove pipes").
$20/cartridge is for single round collectors only. BTW "Uncle Joe" (Salter) likes to sell empty boxes (HUH) for stupid (STUPID) prices so all the the bucket has a value IFF sold intelligently.
All good wishes
OGC