I know that the rifle and carbine buffers are different, but what about the springs? Any difference?
I just removed the fixed CAR stock from my Oly and I want to replace it with an A1 stock. Aside from needing a buffer tube, can I re-use the spring and buffer from the fixed CAR stock?

Yes, there is a difference.  there is even difference between the Colt carbine buffer spring and Bushmaster's carbine spring.  

Thanks for the reply Chen.
Can i re-use the carbine spring and buffer in a rifle buffer tube? Or is that asking for problems?  

Asking? More like guaranteeing damage to your lower receiver.

The carbine spring and buffer are designed so that at total compression in a carbine-length tube, the gas key on your bolt carrier cannot make contact with the top ring of your lower receiver (where the buffer tube screws in).

Putting a carbine-length spring and buffer in a rifle-length buffer tube will allow the gas key to impact the receiver on every shot. It's a toss-up on whether the impact will destroy your gas key or the receiver first ... either way, it won't be pretty, and it'll be expensive to fix.

There IS, however, one way to make it work: Get a piece of wood dowel the same diameter as the inside of your buffer tube, and cut a section that equals the difference between a carbine buffer tube and a rifle buffer tube. Slide it into the buffer tube before you install the carbine spring and buffer, so it sits behind them. This will reduce the effective length of the buffer tube to carbine size. It's not a very elegant solution, but it'll function and, if measured and cut correctly, will prevent damage to your gun.

Since the carbine stock is a fake collapsible, it might use a full length buffer and spring. How does your buffer, spring, and tube measure up (inside depth)? Unless you *know* what you have, fixed stocks can be a giant PITA to set up correctly.

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Thanks guys. I figured it out without breaking anything. FWIW, the CAR stock used a CAR buffer and spring...and the stock WAS the buffer tube. IOW, the CAR stock didn't slide over a buffer tube, the inside of the stock was the tube.