There has been a significant amount of scientific testing yielding repeatable, verifiable, irrefutable factual data rather than mere opinions. For a perimeter role a 5.56 mm AR using appropriate ammunition is probably just fine; it might even be OK as a sniper support weapon as long as shots into vehicles or through intermediate barriers are not a common concern. Having said that, as a LE or military true sniper caliber, as contrasted with DMR or patrol/perimeter applications, the 5.56 mm just does not cut it, as there are far better choices: In a bolt gun, a 16-20" .308 is ideal and if a semi-auto is desired, either a 16" .308 or a 12-16" 6.8 mm is optimal. Night vision capability w/ IR laser designator is an operational necessity; ASA data shows 43% (95/219) of sniper incidents occured at night. Visible lasers are another option that should be strongly considered. Good sound suppressors are also becoming mandatory items.
While snipers like to talk of head shots, there are an inordinate number of torso hits in the law enforcement forensic literature. As posted above, ASA indicates 47% of sniper shots were to the head (104/219), while 53% were to the body (115/219). As a result, law enforcement sniper bullets need to exhibit terminal performance which can consistently induce rapid incapacitation with shots to the torso, as well as the head. If you use a 5.56 mm, what happens when if you have to shoot through a window or into a vehicle, how about if the bad guy has something over his chest--perhaps AK mags? 5.56 mm is suddenly not looking so good:
Superior terminal effects and barrier penetration ability are why .308 dominates LE sniper use; .308 accounts for 74.5% (161/216) of sniper shots chronicled in the ASA data base. Historically U.S. law enforcement and military snipers have chosen the extremely accurate, competition proven .308 Sierra Match King OTM bullets in 168 gr (M852) or 175 gr (M118LR). Unfortunately, the SMK’s have significant terminal performance problems, including very inconsistent behavior, that render them a poor choice for LE sniping. In addition, SMK’s will frequently exit the target and pose a significant downrange hazard to innocent bystanders and friendly personnel. In fact, according to ASA data, 90% of SMK shots have exited the suspect and posed a downrange hazard.
As discussed by both Fackler and Haag, the cause of SMK inconsistent terminal ballistic behavior appears to be associated with the diameter of the hollow point at the tip of the Match King bullet. Match Kings produced in the 1980’s had tip diameters of 0.028” to 0.038”, while recent Match King tip diameters appear to range from 0.012” to 0.024”. The smaller the tip diameter of the hollow point, the more the Match King tends to behave like a FMJ bullet; conversely, increasing the tip diameter enhances bullet upset in tissue. Fackler and Haag both have reported that when the SMK open tip is enlarged to at least 0.055”, the Match King offers consistent expansion and fragmentation with virtually no change in accuracy.
As a result of their mission profile and typical engagement distances, military snipers are less affected by the inconsistent terminal effects of SMK’s than U.S. law enforcement snipers; for military snipers, consistent exceptional long range accuracy is paramount. For law enforcement use, the inconsistent terminal effects of SMK’s can have tragic human and litigious consequences. U.S. law enforcement snipers have two choices to avoid inconsistent SMK terminal performance: Demand that Sierra market specific law enforcement Match Kings with hollow point diameters of at least 0.055” or use a different bullet which offers both acceptable accuracy and more reliable terminal performance. Luckily, several bullets are available which more than meet the requirements of LE snipers, including a variety of polymer tip, JSP, and JHP projectiles. The .308 Hornady TAP loads using polymer tip AMAX bullets offer consistently superior terminal performance compared to standard SMK bullets, although the SMK's are generally a bit more accurate. Are LE snipers willing to trade a slight bit of accuracy to eliminate SMK variability & gain consistently improved terminal effects?
The 155 gr AMAX consistently offers nearly perfect terminal performance characteristics in unobstructed shots--ideal penetration, good fragmentation, and perfectly placed large temporary cavity. All of the .308 AMAX bullets we are aware of fired in OIS incidents to date have remained in the suspects' torsos; damage on autopsy has been quite impressive and exactly as predicted based on lab analysis. The 110 gr AMAX has a shallower penetration depth with a rounded temporary stretch cavity, while the 168 gr and 178 gr AMAX have deeper penetration than the 155 AMAX, with a more oval, narrower temporary stretch cavity. BH also loads AMAX bullets.
Loads with similar ideal wound profiles in unobstructed shots as the 155 gr AMAX include the Nosler 150 gr Ballistic Tip PT, Speer 150 Gold Dot JSP's (and identically constructed Federal 150 Fusion JSP
), Hornady and Nosler 155 gr OTM, Federal 165 gr TRU JHP, Remington 165 gr AccuTip PT, Winchester 165 gr Ballistic Silver Tip PT, 150 & 165 gr Sierra Game Kings.
Intermediate barriers are a significant issue for snipers. As noted, ASA states 23% (50/219) of law enforcement sniper shots involved intermediate barriers, typically glass. Unfortunately, the SMK is NOT a good barrier round.
Glass barriers are one of the most difficult challenges for LE snipers. OTM bullets like the SMK’s generally exhibit unfavorable fragmentation and trajectory deviation when fired through glass intermediate barriers, resulting in degradation of terminal wounding effects. Despite gunstore commando lore to the contrary, FMJ bullet terminal performance is extremely erratic against glass. Bonded JSP/PT bullets and true AP bullets like M993 are often able to defeat glass intermediate barriers while retaining their mass, although they exhibit very deep penetration in soft tissue and can be counted upon to exit the suspect and pose a downrange hazard. In addition, they are not always as accurate as other bullet designs. PT bullets, like the Hornady AMAX and Nosler Ballistic Tip, offer better performance against glass than OTM bullets like the SMK, but are not the equal of bonded JSP/PT bullets or AP bullets. The Federal Tactical load using the 165 gr Trophy Bonded Bear Claw JSP offers superb terminal performance in both unobstructed shots, as well as those through intermediate; it is the most tried and tested barrier blind load, however, accuracy is typically in the 1.5-3 MOA range. Newer barrier blind loads like the BH loaded 180 gr Nosler Accubond bonded PT load and 168 gr Federal Tipped-TBBC bonded PT (LE308TT2
) offer sub-MOA accuracy along with outstanding terminal performance in both soft tissue and glass. Because of their deep penetration characteristics, plan that barrier blind loads will likely exit the target, so be aware of the backstop. Currently the best .308 glass barrier loads are the Federal Tactical using the 165 gr Trophy Bonded Bear Claw JSP and 168 gr T-TBBC PT, Black Hills loaded 180 gr Nosler Accubond PT, Nosler 150 & 165 gr Partition, Remington loaded Swift Scirocco II 150 & 165 gr bonded PT, Swift A-Frame 165 gr JSP, Remington Core Lokt Ultra Bonded 150 & 180 gr JSP, Speer 150 & 168 gr Gold Dot JSP's (and identically constructed Federal 150 & 165 gr Fusion JSP's
), Hornady Interbond PT, as well as Barnes Triple Shock & MRX; all create similar deep penetrating wound profiles. Be aware that while the Barnes all copper TSX/TTSX bullets are great projectiles and offer good penetration through barriers, when first hitting a laminated automobile windshield intermediate barrier, the TSX/TTSX bullets exhibit less expansion than other “barrier blind” loads, as the Barnes jacket either collapses at the nose, the jacket "petals" fold back against the core, or the "petals" are torn off. This phenomena has been documented by the FBI BRF, as well as being noted in our testing.
BH loaded 180 gr Nosler Accubond in bare gel:
-- For military snipers and others needing long range accuracy, the SMK 175 gr OTM is the way to go. Another good long range choice is the 155 gr Lapua Scenar OTM.
-- For intermediate barrier penetration, rounds like the Federal T-TBBC and TBBC, Hornady Interbond, Nosler Accubond & Partition, Remington Core Lokt Ultra Bonded, Swift Scirocco II, Speer Gold Dot and identically constructed Federal Fusion, Barnes TSX/TTSX as well as M993 AP are the best choices.
-- For unobstructed shots, the Hornady 155 TAP offers outstanding accuracy nearly on par with SMK’s, as well as more consistent terminal effects, increased incapacitation potential, and better performance after penetrating through glass intermediate barriers than SMK’s; as a result, the Hornady 155 gr TAP using the polymer tip AMAX bullet is the probably a better choice for LE snipers than SMK's. The Nosler 150 gr Ballistic Tip PT, Hornady and Nosler 155 gr OTM, Federal 165 gr TRU JHP, Remington 165 gr AccuTip PT, Winchester 165 gr Ballistic Silver Tip PT, Sierra Game Kings, and Weapons Unlimited Hostage Rescue JHP also work well got unobstructed shots.
The advent of reliable, accurate, ergonomic .308 semi-auto rifles like the 16" barrel KAC SR25 EMC, LaRue OBR/PredatOBR, LMT MWS, and FN Mk17/SCAR-H allow LE snipers to retire their bolt guns in favor of these much more capable and versatile weapons systems. With properly trained shooters, appropriate optics, and good quality ammunition, these rifles are capable of effectively hitting targets from 0-800+ yards. Some of the characteristics of an ideal performing general purpose rifle projectile are described here: http://lightfighter.net/eve/fo...819863/m/25120859863
as well as in commentary by SSA Buford Boone of the FBI BRF:
-- Penetration of 12 to 18 inches
-- No impact AOA induced variations
-- Blind to barriers
-- No deviation from shot line after impact
-- Minimal fragmentation
-- Consistent terminal performance from 0 – 300 meters
-- Sufficient accuracy to hit threat targets out to 600 meters
The current .308 rifle loads that best meet these requirements when fired from a 16" barrel semi-auto, include the Remington 150 gr Core-Lokt Ultra Bond JSP, followed by the Speer 150 gr Gold Dot JSP, and Swift 150 gr Scirocco bonded PT.
If an organization wishes to retain the ergonomic, versatile AR15 system for sniper use without moving to the larger, heavier .308 semi-auto systems, then the best option is to use an AR15 chambered in 6.8 mm instead of 5.56 mm. Interestingly, for LE purposes, the 6.8 mm potentially allows an agency to use one caliber for all their shoulder fired weapons. Not only does 6.8 mm caliber offer substantially better terminal effects and intermediate barrier penetration capability than 5.56 mm, it is also an inherently very accurate cartridge. In addition, the 6.8 mm was designed and optimized to work effectively in short barrels of 12 to 16 inches in length. The versatility, compactness, potential accuracy, and effective terminal performance of 6.8 mm allows an LE agency to standardize on one caliber and one semi-auto rifle type for multiple uses, including: patrol, entry, perimeter, sniper support, primary sniper, animal control, and personal close protection details. For information on 6.8 mm ammo choices, see: http://www.m4carbine.net/showthread.php?t=19884