What effect does the heavy M4 buffer have in the short barrel (16") carbine?  I seem to be having brainlock as far as mitigating the 'short barrel blues' and ammo sensitivity.  I'd like to know if it will help the short stroke and premature bolt opening problems.  TIA Ops

As far as short stroking goes, It will not make a difference.

Where the heavy buffer shines is in short barrels that open up too fast.  This is caused by the shorter/higher spike in gas pressure  unlocking the action.  The heavy buffer will slow down the unlock and add the extractor from being torn from the case rim.  Also, in 9mm CAR's, the action is blow back, not locked, and the buffer slows down the blow back.  This helps the ammo by allowing the action to stay closed a little longer, and keeps the action a little bit cleaner.

The other benefit is on full-auto Car rifles.  The heaver buffer will slow down the cycle of the weapon, and reduce fire rate. Also, due to the extra weight(inserts), it helps to control bolt bounce a little better than a standard Car buffer.

Hope this helps.