After having some phone time with Jerry Stiller at Stiller Precision regarding the Predator Extreme action, Glen Harrison at Phoenix Machine regarding their action using a .750 bolt and Bruce Thom. at BAT Machine regarding their HRPIC reciever, I've learned a few things regarding the use of long mag boxes like the 4" inside length centerfeed Wyatt's or the 3.94" inside length Seekins DM which seem worth sharing on this thread.
Unfortunately, Jerry at Stiller Precision does not think his Predator Extreme should be modified to work with the Wyatt's or Seekins DM. They would not leave enought meat on the receiver body or the bolt stop. Unfortunately, I've canceled my order with Jerry for this reason. I don't want to spend $$ on a custom rifle
and then be more restricted in magazine length than I am with a factory Rem 700 LA that I can put a 4" Wyatt's box into.
Phoenix and BAT both machine their actions, at no extra cost if they know beforehand, for the Wyatt's or the Seekins in house (and others if you ask beforehand) and either move the bolt stop location or use a different bolt stop to accomodate the long boxes.
Both Phoenix and BAT use CM bolts. Phoenix is one piece and BAT silver brazes on an SS handle.
Phoenix uses 8-40 scope rail screws and M16 extractor standard. BAT's HRPIC reciever has integral 0 or 20 MOA rail and recoil lug. BAT has their own design extractor that Bruce says is very robust for the HRPIC.
The cost difference between these two is negligible when you consider the need for a pic rail and recoil lug for the Phoenix that is integral on the BAT HRPIC.
Just food for thought for those that might be in the same boat I am.