buffer weight

[LRRPF52]

The main reason for the added weight (H buffer) in the M4 was the adoption of the M855 bullet that had a different ogive than the M193 bullet that was causing feed malfunctions, not bolt bounce..

The original fix was the addition of feed ramps in the upper receiver.. Colt then added a tungsten weight to slow the carrier down to allow the magazine time to present the cartridge for proper feeding..Colt maintained the feed ramps as a redundancy for proper feeding and to keep the M4 TDP as Colt intellectual property when the government tried to claim ownership..

https://youtu.be/DYf-MLMODhA?si=zdMg_5I9DaHqUGYc&t=755

They had been shooting millions of rounds through Colt 723s an 727s with extended feed ramps from 1985-1993 until M4A1s were adopted in JSOC in 1994. The extended feed ramps were part of the M16A2 carbines (723, 727, 733) already in the 1980s, along with 1/7 twist for M855. The ogive on M855 is actually more easy to chamber in short throats than M193, since M193 is tangent ogive, and M855 is secant.

Extended feed ramps were introduced on the Colt 723 due to the 2 decades of prior of experience with the CLGS XM177, XM177E2, and RO653 14.5” M16A1 Carbines, which exhibited faster cyclic rates. The increased cyclic rate would sometimes beat the magazine spring lift of the cartridge stack, and slam projectiles back into the case when the meplats hit the inside lower edge of the upper receiver, just below the barrel extension feed ramps. M855 run at 5.56 pressures with the heavier bullet would increase the cyclic rate, especially in hotter ambient temps.

This is where the extended feed ramp design change was made on the carbines. The Colt 723 and 727 laid the core operating system design for the XM4, which began development in the 1980s. Here’s an older Colt brochure on one of the 723 showing the addition of extended feed ramps in the 4th bullet point down.



Here’s another older brochure showing the first configuration of the Colt 723 and 733 Carbine and Commando. There were several different variants of each of these, mainly with different barrel profiles and upper receivers for the 723. Initial uppers lacked the brass deflector, while the newer Abu Dhabi C7 upper with deflector was introduced around 1987 if I recall. Some guys had them and some didn’t in Panama in 1989. The 727 was standard with an A2-looking upper, but had extended feed ramps inside. The 727s all had the stepped profile barrel with heavy fore end with a cut for the M203 bracket. This barrel profile was not on the original 723s, but became more common towards the later years of 723 production and barrel changes by Unit armorers.