" If you want to take it another step further, have a custom reamer made to seat those 156s WAY out there."
Custom reamer is the way to go, I am sure there are quite a few Gunsmiths that have reamers with long throats for the 156s.
In the event you get an already chambered 6.5PRC you can always have a GS use a Uni Throater on it or do it yourself. Be very careful doing it yourself Those UniThroaters cut easy and fast. Use a Modified Case Gauge to determine how much FB you have and need.
If you have a Hornady Gauge and need a case Drilled & Threaded send us a PM. Will make you some for FREE (just $5+) for return shipping.
Thanks
Len & Jill