barrel extension?

[paratroop]

planning on piecing together an ar sometime in the near future and i have a couple of questions. first off, when you purchase a barrel, does it typically have a barrel exrension, and index pin? or do you usually get that separatly? same thing goes for a stock, do they come with receiver extentions, or is that usually a separate part too? or do i have to get more specific because there are too many variances? thanks

[joelukehart]

I've bought barrels from Bushmaster and Model 1 Sales and came with the extension and pin installed. The Bushmaster just needed a gas tube and the Model 1 only needed a barrel nut. The Model 1 didn't need an extension as it is a .22 lr. Most of the barrels you will find are ready to bolt in.

[paratroop]

awesome, thanks

[ar15barrels]

planning on piecing together an ar sometime in the near future and i have a couple of questions. first off, when you purchase a barrel, does it typically have a barrel exrension, and index pin?

Yes.
Furthermore, if the barrel does NOT have an extension, you don't want it.
It's not possible to swap extensions after the gas port has been drilled.