Reply to "5.56 mm Duty Loads"

The Black Hills produced Mk262 uses the 77 gr Sierra Match King (SMK) OTM and is built as premium quality ammunition intended for precise long-range semi-auto rifle shots from the Mk12 rifle. It is great for its intended purpose. Mk262 has demonstrated improved accuracy, greater effective range, and more consistent performance at all distances compared to M855 when fired from current M16, Mk12, M4, HK416, and Mk18 rifles and carbines. However, despite this substantially improved performance, Mk262 is NOT necessarily the best choice for LE or most military combat use from carbines, as Mk262 still manifests the problems of poor intermediate barrier penetration and somewhat variable terminal performance inherent with the SMK design, as well as increased cost.

As articulated by combat AAR’s the last few years and demonstrated in recent military wound ballistic testing, improved combat ammunition that is specifically designed for rifle and carbine use, not machine guns, is urgently needed. New loads should offer:

-- JAG approval
-- Full reliability in diverse environmental extremes
-- A thermally stable propellant
-- Consistent lot-to-lot and shot-to-shot performance, even when fired from short barrel weapons
-- Crimped and sealed primer
-- Sealed case mouth
-- Cannelure for functional reliability in adverse conditions
-- Decreased muzzle flash
-- Acceptable accuracy at 300-500m
-- Good soft tissue terminal performance (early consistent bullet upset within 1 or 2 inches of initial tissue penetration
-- 12 to 18 inches of penetration coupled with maximized tissue damage during the first 10 to 12 inches of travel in tissue
-- Designed to minimize AOA and fleet yaw issues
-- Blind to Barriers

OTM, although a step forward, does not fully provide what is needed in a military setting. Until recently this goal seemed impossible, however “Barrier Blind” ammunition requirements from multiple organizations, including the FBI, USMC, NSWC Crane/USSOCOM, & JSOC have yielded several options from industry that appear to effectively address this issue. For example, see the 01 June 2006 Marine Corps RFI ( for “Barrier Blind” ammunition. NSWC Crane ( has now publicly acknowledged the existence of the SOST cartridges, the 5.56 mm 62 gr Mk318 Mod0 OTM; this is a non-bonded version of the ATK TOTM projectile made for the Marine Corps Barrier Blind RFI, as noted on page 12 of my NDIA briefing from 2008 ( The SOST rounds are optimized for relatively short barrel weapons, use heat stable, flash suppressed powder, and offer good terminal performance, with early upset and reasonably good intermediate barrier performance for a non-bonded projectile. The SOST/TOTM is an outstanding, simple, adaptive design--projectiles can be manufactured with a traditional lead core or in a lead-free version, bonded or non-bonded. The 70 gr Optimal "brown tip" in use by some SOF organizations is another excellent option.

At this time, given the current ammo choices available via the standard green/white side military supply system, for a general purpose carbine, I'd load my mags with Mk318 Mod0 if available. For long range shooting the Mk262 Mod1 is optimal. A couple of mags of M995 AP for barriers wouldn't be a bad idea either.

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