Posted on 10/07/2019 9:46:26 AM PDT by Black_Rifle_Gunsmith
(This post is part of the running hobby topics posted on a regular basis, How to Build an AR-15 and gunsmithing with an 80% lower)
The AR-15 (and its .308 equivalent) is a unique weapon. It's just one of a few weapon platforms that chambers both commercial and military ammunition. While .233 Remington is a universal round, 5.56 NATO is not. There are a plethora of cartridges that fall under the NATO umbrella, each of which is largely produced for the armed forces and the civilian market by the Lake City Army Ammunition Plant.
This guide compares 5.56 NATO cartridges, including M855 and M193, and what the differences are between the two. It also compares the "M" and "XM" cartridges you may find on the ammo shelf.
5.56 NATO: A Quick History
The 5.56 x 45mm NATO cartridge is a .22-caliber rifle cartridge designed for military use in the late 1970s by FN Herstal. The round itself is based on Remington’s hugely popular .223 Remington cartridge, which was developed in 1957 for the original ArmaLite-15 (AR-15) rifle and eventually, the M16 service rifle in 1964. Unhappy with the performance of .223 Remington, top brass in the military (no pun intended) ordered the round to be redesigned to offer better penetration against armor and hard targets at long range. The round was refitted with a 62-grain FMJ bullet that houses a 7-grain steel core penetrator, and thus 5.56 NATO was officially born in October 1980. Today, the 5.56 NATO line of ammo consists of M855/SS109, SS110, and SS111 cartridges. There are numerous specialty cartridges (M199, M196, and others) that are also reviewed in this guide.
I think it has something to do with imperfect placement of the mild steel penetrator within the round.
M855 is the Nickelback of 5.56mm rounds. Everyone likes to tear it down.
In my rifle, with a 1:7 twist barrel, Federal M855 groups better than Federal M193 at 200 yards. IMI 77g match does (unsurprisingly) better than both.
I like M855 as a “do everything” round, that’s cheap enough to plink, plus accurate and effective enough against people and armor.
MK262 is where it’s at, even in sbr’s.
Good stuff, keep ‘em coming.
Thank you for posting these educational threads. It’s a unique and much appreciated resource for this community.
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