I bought a Rock River Tac Entry recently, which I feel is a very nice rifle. This past week I decided to switch the stock. The stubby just didn't work with my long arms. So I got standard AR bufffer tube and an Ace stock. My question is this. Since I switched from the short CAR length buffer tube used by the stubby stock to the longer A-2 tube required to install the Ace stock, should I use the heavier buffer spring like the rifle uses or do I retain the spongier carbine spring that came with the stubby system? The heavier spring seems to make sense to me because of the added length but I figured I should get some opinions on the matter. Any help would be appreciated a lot.

You use the A2 spring that came with the A2 buffer tube, along with the buffer.  Unless you like spending more time fixing malfunctions at the line then actually shooting your AR. [:D]