18" Barrel on a BCM Carbine Lower?

[WVsig]

I have a BCM Carbine lower that I am considering putting a 18" upper on. It has the standard Milspec Carbine Buffer System (Default H Buffer). The rifle upper I am looking at has a rifle gas system. Will the rifle be too undergased?

I have never run anything over a 16" upper in the past. Thanks in advance.

 

[Quentin2]

It should work fine. If weaker power ammo short strokes you could replace the H buffer with a standard carbine weight buffer.

 

[bfoosh006]

Ditto... you should be fine.

 

[marine6680]

I run an 18 inch barrel with rifle gas on one of my rifles, and I use an H2 buffer.

 

[Mobuck]

The lower doesn't care what sort of upper sits on it-unless the upper is out of whack.
Why does this keep coming up? It's possible to interchange ANY upper with ANY lower as long as the pins fit.