Gentlemen,
I need some technical advise. I am trying to swap a CA stock of my Colt A3, and put on a A1 fixed stock. The problem is the locking ring on the CAR stock! I cannot get it to budge at all. I broke one spanner wrench already, and not in a hurry to break another one. I took it to three local  gun shops, none who were interested in working on anything other then hunting weapons. One did take a look at the stake marks, and did not think they were the hold up (Lok-tite?). Any advise on how to complete this project, with out shipping my lower off, for what should be a simple job? Thanks for any and all help.
S/F
Flyingrhino

When a nut like this breaks a proper spaner, you (obviously) have a problem.
What I have done in the past is slice the nut nearly all the way through in such a way as you don't cut any treads on the receiver extension since that is a pretty valueable part. The cut is in line with the bore from rear to front. With the nut cut nearly through, there should be some degree of stress relief.  Attempt now to drive the nut lose with a hammer & punch, with the punch in the slot you just cut.
If the nut won't loosen, cut another slot a little ways from the first one and try the punch again.
I use a dremel tool with a Heavy Duty metal cutting wheel, or I double-up on two of the normal thickness disks to get a bigger slot.
If you are also not concerned with the carbine receiver back plate, you can cut a little into it so you weaken the "ring" of the nut all that much more.
I make my cuts on the right side near the 2 o'clock position on the nut so I can lay the receiver down on its left side.  This positions the punch so the hammer blows will tend to make the nut rotate.  Nut rotates off in the counterclockwise direction when viewed from the rear of the gun.
I have used this same technique with old shower values when wrenching a coroded nut too much would break the pipes behind the wall and cause a leak that could only be fixed by taking out the wall behind or the shower enclousure, but that's another story...

Heat sometimes helps to loosen a frozen nut.  Make sure to remove anything that could be damaged by heat - buffer and spring to start with.  Keep the heat on the nut - not on the receiver.  Just a thought, before you start cutting.

I had another possible alternative, as this morning I re-configured my carbine for some range shooting by replacing its normal short barrel CQB upper with a varmit scope mounted 20-inch barrel FF upper, and sliding off the Vltor carbine buttstock, and then sliding on a Vltor A1 length buttstock.
In this way you get the rifle length of pull you want, you don't have to risk damaging your lower receiver, and you can very quickly go back to the colaspable carbine buttstock in a few seconds without any tools.