For a short time back in 2013, the USMC considered adopting the M16A4 PIP program (colloquially M16A5) after experimenting with collapsible stocks on the M16A4 for some time. Upgrades over the original M16A4 considered in the program include a Daniel Defense Omega 12 two piece free floated rail and Vltor A5 stock system that could be installed by a unit armorer without permanently altering the weapon.
Vltor produced a proprietary intermediate length buffer tube and M16 + heavy buffer weight in order to retain the rifle length AR reliability, smooth operation and overall function while utilizing a collapsible stock from the carbine. Sadly, the M16A5 concept was dropped. The USMC adopted the Army M4 instead until the switch to the M27.
But the concept lives on for the musket aficionados like myself. I believe this rifle would have been the ideal 5.56 general purpose combat weapon. The Canadians were onto something with the Colt Canada C7. I own several AR examples. From a lightweight sub 6 lb carbine to a heavy LPVO equipped SPR. My favorite has always been La Longue Carabine. The longbow. The killin’ rifle. She never fails to impress.
The 20 inch AR is a super smooth operator. Recoil is reduced, concussion and muzzle flash is a mere shrug and muzzle rise is exceptionally low. The rifle-length AR is king. Is this an ideal CQB or MOUT weapon? No, but it can do the job just fine with proper technique like short stocking. The rifle length gassed system and barrel offer peak 5.56 performance and does so with the upmost reliability as designed by Mr. Eugene Stoner.
77 grain OTM MOD 1 5.56 from a 20 inch barrel will fragment out to 350-400 yards. This is good. Maximum lethality from the 77 grain OTM cartridge. The weapon isn’t too heavy, which is a plus given the capability. Although a pencil barrel profile would’ve been preferred by me. I may have ADCO turn the barrel down past the gas block sometime in the future.
This is my go-to AR for dedicated combat from 0-600m in the event of alien invasion, zombie apocalypse or hostile communist insurrection. The fixed FSB should be a requirement on a hard use AR. The option of the bayonet and the ruggedness of the fixed front sight post shouldn’t be overlooked. You can turn your rifle into a ****ing spear if need be.
Specifications/ my interpretation:
1.) PSA CHF 20 inch FN barreled upper. Routinely puts 5 rounds of 77 grain match in just under 1 MOA at 100m.
2.) Vltor A5 Stock System
3.) Daniel Defense 12 inch Omega free floated rail (discontinued)
4.) SSA-E trigger
5.) KAC foregrip/ A2 grip for the feels
6.) Trijicon TA31F ACOG RCO w/ RMR type 2 3.25 MOA
7.) Troy rear flip up battle sight
8.) Colt LE6920 lower
9.) NibX BCG
10.) Smith Vortex flash hider
11.) Surefire M600DF WML
I know the Corp has been getting the money it deserves, or at least more of what it should be getting. 
