Hi Buckmastr,
I don't think there were ever any Major issues necking up 6.5 x 284 other than the few cases of doughnut sometimes appearing. This is from various forums I've looked at in relation to necking up. I purchased Lapua Brass & a K &M mandrel to do just that but I've not tried it yet so, no experience!
Now that Norma are doing straight 7mm 284 brass,obviously I would prefer to try it.
Thanks
shona