I do have an email in to AINA. I just thought someone here might have experience with this. I am talking the AX338. The non skeletonized butt stock with the tubular forend.
It should work, but checking with them is a very good idea. I've honestly never tried to switch the firing pin assembly around between a pre-2014 AX and the AXMC shrouds myself. AINA is just going to point you towards Mile High most likely by the way.
I have an Pre 2014 AX338 and thought about a 300 win mag. Mile High told it was not practical because it becomes more than a parts switch because there was no AX300 win mag manfufactured by Accuracy International. Ray