Has anybody out there built anything big on the Montana rifleman magnum action? By big I mean something along the lines of 500 A2,500Jeffery?
Also I am going to put out the question-which caliber,500A2 or 500 Jeffery?

The PH magnum action is not available yet. You do not need the PH action to build a 500 AS or 500 Jeffery. The CZ 550 Safari and BBK-01 UltraMag should be more than big enough for these cartridges. I will take the 500 A-Square over the Jeffery for a 50 caliber bolt action. Thanks.

I am going to answer my own question. the Magnum action wont handle the bigger cartridges,If I want to use a Montana Rifleman action I am going to have to wait until the PH action is available,that is according to one of their sales reps. Now I guess i will have to get a cz 550 for this project!

The 500 Jeffery is plenty short, at less than 3.48" COL. The sales rep either misunderstood or was wrong.
Actually, if you can stand the thought of going from the 500 A-Square's 8150 fp of muzzle energy to a mere 6900 fp, the 496 A-Square fits in a 3,6" magnum action as well.

If you want to correct A-Square's mistake, you could have a reamer made to the 500's dimensions, and just move the shoulder back .10", trim to 2.8", load to 3.6" COL.
You could use the 500's dies cut off at the bottom, it would chamber it in a magnum action, and you'd have a case with 141+gr of water capacity, as opposed to the 495's 133gr. The 500 only has 147gr or just under, so you're better than halfway between them.
That should get you 2400 fps with a 600 grainer, and only add the cost of a reamer to your rifle.
Have John Ricks do it, and he'll split the $150 reamer charge with you, he keeps the reamer, and cuts it based on the actual dimensions of your cases.
What do you say?
You could call it the 500 Proper.

[Do it!]

It's not really a question as to whether the bolt face could be opened up for the Jeffrey (.575" according to Cartridges of the World 8th Edition) or the length of the cartridge (3.47" again according to Cartridges). The question is the diameter of the cartridge (base diameter of .620") compared to the thread diameter of 1". The 1" is the outside diameter, you would end up with less than .150" on each side of the chamber. If you overloaded one cartridge and bulged the chamber, there isn't much between that and the receiver. For us it is more a safety issue than a "is the action large enough" issue. We've built in a lot of safety in this action and do not want to recommend something that we don't feel is safe. Hope you understand that.

Check!
Diesel Dude, want me to send you the specs on the 500 Proper?

Bwana-be,send me those specs! Has this ever been done?