Any pistol buffer tubes that will let me run a rifle buffer tube/spring?

I have been looking to make a Sig Arms brace AR pistol but have been thinking about taking a Vltor A5 tube and having a machinist buddy mill it down so that I could fit a Sig brace on there. Before I go through all the trouble is there a pre-existing product on the market that is already filling the niche?

I’m running a rifle RE and Sig brace but I had to build the diameter up with gaffer’s tape to get it to work

The KAK Industries tube takes a carbine spring and buffer.
Check out the phase 5 tubes as well. I don’t have one, and don’t know about the buffer and tube, but a lot of guys are using them.

Yeah I have checked out both of those - I’d really like to be able to use a rifle buffer or a Vltor A5 if possible. The KAK tubes do look nice.

Midwest Industries also has a new pistol buffer tube that will accept the SIG Brace.

http://www.midwestindustriesinc.com/index.cfm?fuseaction=category.display&category_ID=1273