Ian reads these forums, he knows about the posts here in regards to the 450 conversion you bought. The original owner never contacted him about having any issues with it, just posted here and sold it.
It is likely a headspace issue because remington and hornady have quite the variance in case lengths. If you reload, you can likely trim the cases and it will work fine, if not, send it to Ian.
While you are at it, get his custom bolt and a 30AR barrel and you can shoot both calibers from the same bolt and mag, just swap barrel assemblies.
I will buy the 450 if you decide to sell as is.
