All AR rifles with the carbine-length gas system have faster, rougher extraction which occasionally contributes to problems.  It's because the gas system is much shorter, and under higher pressure due to the gas port in the barrel being closer to the chamber.  This means that it is a bit less forgiving of other problems than ARs with the rifle-length gas system.

Of course, the problems weren't severe enough to prevent the whole US Army from adopting the M4 to replace the M16A2 (bad move IMO, as the M4 is really a dedicated CQB weapon, not a general purpose weapon).  But civilians like to shoot cheap, questionable ammo loaded with different powders and bullet weights, which can exaggerate the problems.  The military shoots a few high-quality loads that are pre-tested with the rifle, and don't have as many problems.

-Troy

Re: extractor spring insert colors

The inserts are the same, other than being blue or black, that's true.  The reason they are different colors is to differentiate between the spring itself (the spring and insert are sold as an assembly).  The spring that comes with the blue extractor insert is stronger than the standard one with the black insert.

-Troy

Duh, yes, I did.  In my haste to make the point that the inserts themselves aren't functionally different (but that they are intended to indicate differences in the spring), I reversed the colors.



That's more or less correct, except that they are adopting M16A4s (which are M16A2s but with a flattop upper) in larger quantities now.  I was referring to the original decision several years ago, which WAS to change the whole Army over to the M4.  The Army still uses them in a general purpose fashion too much IMO, though.  Note that the vast majority of the pics you see in Afghanistan show soldiers with M4s, though some M16A4s are coming online.

I wasn't trying to imply that the M4's well-known rougher extraction was a serious problem.  Is it more sensitive?  Yes.  Enough to hinder reliability significantly?  No.



My military experience consists of turning down an Air Farce contract when I was 17 and seriously considering flying jets.  Somehow, at 17 and with 12.5 years of school behind me and "freedom" beckoning, I couldn't bring myself to indenture myself for another 8 years.  It's a choice I've come to regret just a bit over the years.  Unfortuantely, I was 23-24 before I started learning anything substantial about the military and guns, or I might well have chosen a 3 year infantry contract.  If I knew then what I know now...  But then again, being in the military under Klinton wouldn't have been all that wonderful.

So, yes, *officially*, I'm a pogue wanna-be.  I've never tried to imply otherwise, but if somehow I've made that impression, I appologize.  I have nothing but the highest respect for the men and women who serve or have served.  I'm an odd-ball in my family, being one of the very few who has not over the last 5 generations.

On the other hand, I'm an ametuer ballistics researcher, which has resulted in contacts with a few extremely knowledgable folks on the bleeding edge of weapons and ammo development.  I have been fortunate enough to have pretty extensive access to an incredible number of guns, including a number of full-autos, beyond anything I'd ever have dreamed 10 years ago.  Plus I've gotten to know folks at a number of gun-related companies and sometimes have access to some "inside" information.  

Last, I've spent 6 years on the board here, reading and participating daily with some of the finest folks there are, and I've learned a hell of a lot from them.  I've also moderated for 4 years, and have written several (extensively peer-reviewed!) FAQs that are posted here and around the net.

Hope that helps set the record straight.

-Troy