kellyz,
I have an older Rem 700 30-06 ADL that I was considering as a donor for having a 338 Edge built if it is suitable?
You can convert the M700 LA to suit your desired chamber. But, as stated, there are a bunch of adjustments which need to be machined into the action in order for it to feed reliably.
-open rails.
-move (cut) ejector back.
-open magazine cut out to the rear.
-adjust (machine) feed ramp
-gunsmith tuning of the entire assembly to guarantee feeding and function.
Would this bolt from Pacific Tool fit the bill
Personally, I would buy the PTG (with the swept back handle for Rem.) and have that part taken care of correctly from the start.
Also, can the Wyatt's extended box mag be used for long COAL (~3.900") loads with this action?
The MBE-3 box will work for this application but remember that it is the interior measurement (3.825") you want to pay attention to, not the exterior measurement (3.900"). Also, the MBE-3 is for a BDL trigger guard so you need those parts as well.
The end result is an action which has had irreversible machining done to it which makes it dedicated to this or very similar cartridges. The dollars put into this conversion may not be worth the conversion when compared to buying an action purposefully designed to accommodate these cartridges for reliability. I know, you think by cobbling an existing action together that it will be much less expensive. Maybe but probably not.
Get quotes from several gunsmiths who are qualified. Yes, qualified. Some are much better than others.
Look around at some of the actions available for this cartridge and other similar ones. You might be surprised at the comparison.
Regards.