It doesn't matter because either way it's arbitrary. Either they arbitrarily placed it to accommodate a bayonet, or to be able to fit a standard FSB on a 10" barrel (or both). The pertinent fact of the matter is that no advanced engineering or even much thought went into any of the system lengths, and they all have their advantages and disadvantages.
However it came to be I’m gonna stick with it.
I don’t have any gas blocks or mid-length gas tubes so I’m gonna throw a rail on the Colt and rock on.
Hell I’m 40, been shooting 16” carbines since I was a kid, might and stick with the old and outdated theme!
Real world use: quality company with adherence to good specifications.
Want to geek out - exact gas system length for the bbl, exact Gas port, perfect buffer.
You can't take any part in isolation either. Cheap midlengths suck more than properly ported 16" carbines
Last edited by MegademiC; 03-31-21 at 08:25. Reason: Remove retarded comments
There are plenty of printed paper books you can find this stuff in, in buildings they call "Libraries." You can even borrow them for free on "Inter-library loan."
The carbine gas system started with the ten-inch XM-177, then developed to the 11.5 and 12.5 XM-177E1s and XM-177E2s.
In the late 1960s and early 1970s Colt ran into the State Department and their (and Congress') policy (not law) of not allowing suppressor exports due to their being likened to "Assassin weapons."
Removing the XM-177 "Suppressor" did not do any favors for operational reliability, so extending barrel length forward of the gas port /sight to the same profile as the M16A1 ironically improved cycling, allowed use of the XM-177 buffer, but most importantly was now OK for export.
Thus was born the M16A1 Carbine, known affectionately by the Armed Forces of the Philippines as the "Baby Armalite" -- the world's largest force (along with the Israelis) to employ the M16A1 Carbine until the M4.
Colt made a sale of the M16A2 Carbine to Abu Dhabi with the now-familiar M203 barrel cut, thus becoming the "Abu Dhabi Carbine."
The Marine Corps made the effort to product-improve the M16A1 Carbine as a formal "Program of Record," thus getting XM4 R&D monies in the official USMC program and budget. The United States Special Operations Command jumped on that bandwagon as well, and the combined Marine and SOCOM numbers made sense for both Colt and Congress. XM4 became SOCOM's M4A1 (with flat-top) in 1993 while Johnny-come-lately Army exercised the Marines' contract option, planning to outfit the 82nd Airborne, 101st Airborne, 10th Mountain Division, and radio operators, medics, radiomen, crew-served weapons crews, MPs, and aircrew with M4s (with M16A2 uppers, then changing their minds and going with flat-tops).
The Marines, who had taken on XM4 as their program, didn't start transitioning from M16A4 to M4 until sometime in the last five- to ten years.
Mark Westrom, seeing that standard, non-NFA rifles need a barrel with a minimum 16-inches anyway, designed the mid-length gas tube and barrel arrangement to improve carbine cycling. Somewhere in there Knights designed their "Intermediate" gas length.
Colt 633 and 733 Commandos took a little longer for Colt's engineers to figure out, followed by the H1 buffer.
Anyone who has trained in bayonet fighting and technique know the pig-sticker on a carbine or SMG is pretty much useless. You really can't exercise a "Smash," "Slash," or "Parry" very well with a short plastic and aluminum weapon (against something like a Mauser, Enfield, M1, or Mosin-Nagant).
Given that the M1 Thompson submachine gun is 31.9 inches long, the M3 "grease gun" submachine gun is 29.1 inches long, I don't think the 31 inch overall length - and therefore the 10 inch barrel length - of the XM177E1 "submachine gun" was chosen at random or arbitrarily.
" Nil desperandum - Never Despair. That is a motto for you and me. All are not dead; and where there is a spark of patriotic fire, we will rekindle it. "
- Samuel Adams -
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