Are there any issues with the carbine length gas sysytem on the DPMS carbines?  

Can the 16" barrel be shortened to 14.5 inchs w/o any issues?

Thanks!

Heavier buffer is recommended.   Your options are limited there.   Slash buffer if you have an AR-15 buffer tube; or swap to an AR-10 tube which is 5/8" longer and then you can run a regular AR-15 H3 or 9mm buffer.

The gas system should be fine.  Armalite uses more of a midlength with their 16", so 14.5" should have plenty of dwell time with carbine gas.

Cutting to 14.5" should work fine.   While you are at it, I would get the barrel re-profiled [turned down] to loose some of that meat under the handguards.   ADCO seems to be the shop of choice for this.

14.5" requires a perm-attached muzzle device, so pick the one you want before hand.   FSC30 has a good following.
FSC30 link  That model is 2.75"  so you could cut to 14"  and still make 16" with the FH and upto .75" threads.  All the more reason to pick your muzzle device first.

thanks for the info...If I pick this up, it will go off to ADCO.

FYI:
http://www.ar15.com/forums/topic.html?b=2&f=130&t=177784

Yep, saw that....very nice!