In the end, you'd probably be better to just get a second upper half. Besides, this would give you options when you wanted to flex the a rifle into a different role.
Of course, it's simple enough to swap to a different barrel, provided you have the tools and the know-how. In fact, if you choose to go this route, you may want to consider a "disippator" barrel...16" with rifle length handguards. DPMS, Del-Ton and other manufacturers make them.
Take note, however, that there are two kinds of "dissipator" barrels...those that have a rifle-length gas system...and, those that utilize a mid-length or a carbine-length (it varies by manufacturer) gas system that resides underneath the handguards. The latter utilizes a handguard retainer that is affixed to the pinned FSB.
I prefer the rifle-length version myself. In fact, I used a 16" DPMS dissipator barrel on a A2 build project I did last winter. I left this one without any tactical bells and whistles; just a straight-forward AR. But, I really like the look and feel of the rifle.
This is what mine looks like:
DPMS Tactical 16
FYI...I used RRA receivers for this build, along with the DPMS dissipator barrel and A2 buttstock, as well as DPMS internals.
Let us know how it goes.
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