A2 buffer w/ spacer in a carbine buffer tube?

[LRRPF52]

So I was wondering can I put a A2 buffer w/ spacer in a carbine buffer tube? Will it have enough room for the bolt to cycle? Something like this http://www.dpmsinc.com/store/products/?p...7&cat=1719

Or is the h3 buffer essentially the same weight as the a2?

That rifle stock extender is for a rifle-length extension tube. A rifle-length buffer will NOT work in a carbine-length extension tube-the bolt carrier group will bottom-out before reaching the cycling distance necessary to eject or feed. What are you trying to do exactly?