20 inch upper on a carbine lower.

[airborneski]

I was thinking of getting the . 450 bushmaster upper. I like the looks of the 20 inch better than the 16. Will the combo of the rifle length upper work ok w/ the carbine lower? Vice versa how well does a carbine length upper work with a rifle length lower?

[Optimus Prime]

The lowers are the same, as long as you have the right stock/buffer/buffer tube combo it should work fine.

[airborneski]

That's what info I need, I mean't a carbine lower w/ carbine buffer and spring, and a rifle lower w/ rifle buffer and spring.

[Optimus Prime]

Yup, as long as you have the right size buffer in the corresponding buffer tube, barrel length won't make a bit of difference. The important thing is that a "rifle" buffer is longer than a "carbine" buffer, so it won't be able to move far enough back in a "carbine" tube to cycle the weapon.
The Canadian Army has been running 20" uppers with collapsible stocks for years.

[airborneski]

Great, thanks for the reply, I learned something new today.

[GaCop]

I was in Afghanistan in 07 at Kandahar AB. The Canadian C7 did indeed have the carbine butt stock set up. They also use the Elcan optic on the flat top receiver. The system makes sense when your wearing heavy body armor and a tactical vest.

Tom