Why can’t people just buy a gun based on what works best to create their desired configuration?
My wonder is why no one has done an extended rail with a cut out for a middy FSB and rail at 12 o’clock in font of it. Isn’t there room on a 13" rail?
I hope that was intended to be rhetorical.
A 12" rail with a cut out, like this, would need to be around 14" to accomplish the same feel. Not sure about you, but I think that pushes things to near excessive.
I should probably clarify that I didn’t mean the 14.5" Middy was unreliable. All I meant to say was that we hear complaints now and then and it’s usually when someone is dicking with it. My experience with the BCM 16" Middy and my SR15’s is that they would run reliably with any ammo I ran and a few different lower configurations like the standard A5, a carbine or an H buffer. I’ve never seen one choke unless there was a bad mag or some other outside cause.
My limited experience with the 14.5" Middy is the same, but I hear a lot more issues here on this forum with it than I do the 16" Middy or 14.5" carbine.
For me, I’m sending my SR15 off to have the URX II replaced. Ice started thinking about selling the barrel and bolt and replacing the barrel with a 14.5". So, I’ve been thinking a lot about which gas system to go with if I do. Purely from a reliability aspect, I think the carbine is my first choice though I’m still debating.
Correct me if I’m wrong here, but there’s no milspec on the 14.5" gas port, each manufacturing may do it differently. I know Noveske uses larger ports than BCM and LMT, so that will affect my decision as well.
Didn’t meant imply they were horribly unreliable and get people worked up! 
I started this based on thinking of a new build, and then was reminded by Grant that LAV preferred the carbine setup. I have the basic DD M4 with FSP rail, and the next I was considering a middy. But, having a 14.5" lightweight barrel with FSP rail sounds like a very nice setup. My son has a 16" middy, which feels pretty good, but with a manual light/switch, you cannot get your hand as far fwd as I might like. I am starting to realize that the basic FSP carbine setup MAY be a good thing, still ready for prime time. Right now I have a light on a DD off-set mount and that is fine, but not very ambi. Also, I would like to have a sling mount more fwd, so slinging over the back is easier. But, an X300 gives a few more options. Thus, I can see the reasoning behind the LAV setup. BCM has a LW 14.5" upper that is about perfect albeit without CHF barrel - maybe not a big deal.
I also suppose that DD and BCM use a well thought-out gas port to keep wear to a minimum?
If you pick up a tad bit in reliability, then that might be icing on the cake. Again, seems like the majority like the ‘tad more’ in less wear than ‘tad more’ in supposed reliability these days - hence, the popularity of the middy.
I do think (from reading) that the right carbine gas port also makes a difference. Wonder how these stack up with BCM, DD, LMT, PSA, etc.
BTW - thanks all. Glad this didn’t really turn into a carbine/middy war.
There isn’t anything wrong with a carbine gas system on a 14.5" barrel. Not too much different from running a mid-length on a 16".
But guys take a 14.5" mid-length, and want to start dicking with buffer weights and can’t grasp why it doesn’t lock back on every mag on PMC Bronze.
The only thing I have against a 14.5" barrel is having to deal with a pinned/welded muzzle device. Heck, if it wasn’t for NFA, I’d probably be running a 12.5" Noveske.
I think that I understand what you are saying, but still, isn’t the center of mass further forward on a middie and not a carbine?
I’m not the tallest guy (5’9") so it seemed that the only reason that I needed the extra length of a 9" handguard was to support the weight that was balanced further out front.
I dont know. The same reason someone would buy an upper based almost entirely on hype I guess???
Not to mention, those SAME PRICE uppers come with NO handguard. Taking the FSB off only takes a minute
I was originally attracted to the mid-length M4 as a way to extend the life of the bolt and gas port due to the mid-length gas system being less punishing to them. The trouble is, it’s an improvement but not a solution. Remember even Filthy 14 eventually broke a bolt. Maybe it went a few thousand rounds longer than a carbine would have; maybe not.
It seems the only way to really extend component life is to go rifle length.
So that leaves milder perceived recoil and extra rail area as reasons to own the middies.
I certainly can appreciate the extra real estate for hand placement on the mid-length, but recoil of the M4 is already pretty mild compared to some of the bruisers I’ve fired.
Maybe LAV simply prefers the carbine length, and doesn’t see that much of an advantage to the mid-length. He seems to be a “keep it simple, stupid” kind of guy (I’ve never met him), so maybe he just errs on the side of his extensive experience with the carbine.
It seems the only way to really extend component life is to go rifle length.
I don’t think thats really true. I’m sure in the history of M16s, there have been more than a few broken bolts on full size rifles. Any mechanical device is subject to failure. Guns are built around certian specs, such as MPI/HPT to reduce unexpected failures.
IIRC, 14 made it way past the expected service life of the parts. If you replace parts on a PM basis based on round count and inspection, I doubt you would ever see any serious issues.
This is also a reason why I may consider a 16" “dissipator” build, which provides PLENTY of rail/handguard space, a middy system, and FSP. In this mode, I can mount a cheaper but good light on the right side and operate it well with either hand, AND still have plenty of room for the support hand in various positions, and sling mount.
Otherwise, the FSP rail and X300 setup is pretty good.
It would be nice to know how a properly ported carbine really fairs against a middy in terms of longevity.
This thread inspired me to go shoot an old Colt 16" that I had Robb Jensen put a Daniel Defense Omega X FSP rail on. Irons only. With an H3 buffer and Sprinco “red” spring it was very enjoyable to shoot. No failures to lock back with XM193, PMC, or IMI.
I had just cleaned the barrel prior to this outing, and its accuracy certainly hasn’t degraded.
There have been many improvements to the system since overgassed and underbuilt M4esque carbines first flooded the market: heavier buffers, better action springs, better extractor springs, duty quality compensators, better bolts, improved recoil systems, better knowledge on proper porting and assembly, etc.
If I got a free carbine gas upper I would merrily stick it on one of my lowers and shoot the hell out of it. When it comes to 16" guns, I prefer mid-length gas system, but I don’t think it’s a necessity any more than an A5 recoil system is.