I have a Bushmaster 20" A2 profiled "postban" barrel that is rotting on my shelf.

You folks with 18" and 17" barrels, are you using an unaltered rifle-length gas system?

Thanks in advance,
Jim

I have an 18 with unaltered gas system, with a bigger port and recoil spring mods you can cut it to 16".

Combat_Jack,

Thanks for your reply.

I asked one of the most highly regarded vendors/smiths on ar15.com and their response was that they are reluctant to do a 16" conversion.  

The barrel is in great condition and is nearly virgin.  I would like to do a "dissy" build or at the very most go 17".  If 18" is what's needed to get the gun to work reliably, I wouldn't mind going 18" as well.

Are you running your 18" rifle-length unit with any sort of recoil spring "mods"?

-Jim

I haven't fired my 18 yet, but about a dozen or so guys here, at least, have used 18s without any mods at all.

Olympic Arms' smiths wouldn't cut the barrel down to 16 for me, they said it was was iffy.

my 18 is running 100% with a stock RRA  M4 buffer. Gas port is stock,AFAIK
Barrel was cut and contoured by ADCO

I have a FNMI 5.56 NATO 1/7 that I had KKF cut to 18" with no gas system mods.  I run it with a carbine buffer in a M93A stock and use an RRA bolt group.

I tried it once with a rifle buffer system when it was sorta newish, 350 or so rounds without being cleaned.  The 45 grain Winchester varmint stuff from wally world was starting to get sluggish, like it was barely making it back the full stroke.  All the 55 grain FMJ commercial stuff was still running fine.

I had a few problems with some silver bear stuff with a carbine buffer system when it was still new.  Less than 200 rounds.  It would short stroke if you didn't have it against your shoulder.  I wanted to fan the trigger, but it would just shoot once and end up closing on an empty chamber.

I currently have about 700-800 round of wolf 62 grain through it with no cleaning.  Just a bit of oil here and there.  It is definately filthy on the inside.  You know that black paint that football players put  underneath their eyes?  I make that in my gun

I have thought about trying an H buffer to add a little more mass but I don't know.  I have always kinda had this little monkey in the back of my mind that keeps saying that it is undergassed and will fail me if I ever need it.  Keeps telling me that I need to pull the front sight and open up the port a bit.  Then reality kicks in that I have run nearly 1000 rounds of wolf though it without cleaning and it never even started to get sluggish.  One of these days, I'll lock and load a mag of wolf in it, put it in the freezer for a few hours along with 3 more loaded 30s, then pull them out and shoot them all up as fast as I can just to see what happens.