Since the earliest days of the patrol rifle movement, some officers have chosen a larger caliber than the .223 Remington/5.56mm.
When military surplus rifles were released to U.S. police agencies, some chose the 7.62mm NATO caliber M14 rifles over the smaller and newer M16A1s.
Most of those who chose the M14 were rural agencies, like state police, county sheriffs and game & fish departments, especially in the western states.
Why police officers choose a larger caliber
The 5.56mm cartridge has always been a marginal performer, especially in terms of deep penetration in large creatures, and we shoot more injured or dangerous animals every year than we do felons.
Loads like the Federal Tactical Bonded; the all-copper, hollow-point, bullet-based rounds; and the Mk262 Mod 1 load used by military SpecOps units, have dramatically improved the terminal performance available from M16/M4 carbines, but the 7.62mm/.308 Winchester round delivers a whole different level of ballistic “whup-ass.”
A few years ago I was evaluating a Colt LE901 carbine in 7.62mm. A buddy and I were firing side-by-side at steel plates at ¼ mile (440 yards). His “tink, tink” 5.56mm hits were puny compared to the heavy “ker-schmack” impacts from the big Colt.
Another reason to choose a larger caliber AR carbine is to equip a police designated marksman (DM). A few years ago I proposed that police agencies embrace this military concept, a carbine equipped with a magnified optic for increased distance and precision, giving patrol commanders near-sniper level capabilities without waiting an hour for a full-fledged SWAT marksman to arrive.
Upping the caliber of a DM carbine gives us increased penetration for dealing with light-intervening cover, while also delivering devastating one-shot stopping power.
A torso hit from a 150-155 grain-expanding .308 bullet should ensure an immediate stop on any felon and most animals up to perhaps 400 pounds.
If you think a .30 caliber projectile is too powerful for your locale, most makers are now chambering their AR10-size rifles for the 6.5mm Creedmoor, an intermediate power cartridge.
The .308/7.62, however, offers less expensive military (M80 Ball) ammo for practice and training.
Testing the Smith & Wesson M&P 10 Carbines
Recently, based on a colleague’s recommendation, I had Smith & Wesson send me one of their M&P 10 carbines as a test base.
An advantage of the M&P 10 is its light weight at just under 8 pounds. Since you will be adding an optic, weapon light and, for DM use, a bipod, starting with a lightweight carbine keeps the overall weight manageable.
My philosophy calls for a DM rifle to be capable of CQB work when needed so a package weighing much more than 9 pounds (11 pounds with a sling and loaded 20 round magazine) gets cumbersome. Such capability also requires a scope that will dial down to 1x – no magnification.
While breaking in the barrel and checking velocities and accuracy, the S&W carbine proved it would deliver near-sniper grade accuracy with some loads.
Several ammunition companies load plastic-tipped bullets in the 150-155 grain weight range that will match the trajectory of less expensive full-metal-jacket loads for training. The expanding “tipped” bullets also offer devastating terminal performance on animate targets up to 300 pounds or more and are less likely to over penetrate as open tip match bullets are prone to do.
M&P10 evaluation package
My evaluation package combined the S&W M&P 10, which came with Magpul MOE furniture and backup sights, and a Leupold VX-6 1-6x scope in a LaRue QD mount.
For a heavy patrol rifle focusing on CQB to patrol distances, a 1x optic like an Eotech or Aimpoint would save several dollars and ounces.
For a weapon intended primarily for DM use, the magnified optic plus a bipod will allow precise hits to extreme police gunfight distances.
The M&P 10 barrel is a few hundred rounds from peak accuracy, but will already keep three round groups under 1 MOA with selected loads.
The M&P10 comes with an 18-inch, pencil-weight tapered barrel, rather than the typical 16-inch M4 carbine-length tube. This adds little to the overall length, but increases the muzzle velocity about 50 feet-per-second and slightly decreases the muzzle blast that comes from burning twice as much gunpowder per shot as a 5.56mm round.
While S&W came with a specially designed flash suppressor, I substituted a BABC (Big Ass Battle Comp) compensator from Battle Comp Enterprises.
I did a review several years ago on Battle Comp’s first 5.56mm model and it dramatically reduced the recoil and muzzle rise on a Colt 5.56mm M16A2 carbine, especially on full-auto.
While the.308 caliber AR rifles are not uncomfortable to fire, a BABC can reduce almost 50 percent of the recoil and drastically cut the muzzle rise, helping you stay on target for quick follow-up shots.
I had two complaints:
1. The M&P10 I received had a Magpul pistol grip that was not fully seated on the frame and lacked the grip screw and lock washer. Unlike my normal experience with Magpul’s excellent products, this particular pistol grip was poorly made and required some whittling to get it on the frame (another Magpul pistol grip slid onto the frame easily), but the rifle should have never gotten through S&W quality control as it was.
2. The rifle only came with a single Magpul 20 round magazine. No serious semi-auto weapon should ever come with a single magazine. The various 7.62mm AR rifles must be selling very well, because I had to scrounge far and wide to find two more 20 round mags.
Magpul also makes 7.62mm LR/SR magazines in 10 round and 25 round configurations (the 25 rounder has a window which shows the remaining round count). A special variation is produced for the M118LR military load that uses a 175 grain Sierra MatchKing bullet and is loaded to a slightly longer-than-normal overall length.
The dedicated M118LR magazines should fit into any rifle compatible with SR25-pattern magazines, but being slightly oversize they usually won’t drop free when you punch the magazine release.
The M&P10 has ambidextrous magazine releases and bolt releases. The single-stage trigger breaks at just over 6 pounds and while a little creepy, is better than most stock AR triggers.
Since my DM prototype is intended for precision use, I will probably install a Geiselle SSA two-stage trigger. The SSA trigger has a 4.5 pound total pull weight with the final stage breaking at a light and crisp 2 pounds. I do not recommend anything but a single-stage trigger of 5-6 pounds pull weight on a patrol rifle, but on a precision rifle with magnified optics, a lighter, high quality trigger has merit and the Geiselle trigger is absolutely reliable, and in use with many military units.
Conclusion
When I wrote my first article promoting “patrol rifles” in 1984 I said the 5.56mm round was almost ideal for human targets with the right loads.
Now, after 30-plus years of evolution, we have ammunition that offers even better 5.56mm performance. But the power and reach of a heavier round provides a capability a few of our officers should have.
Coupled with a magnified optic and bipod, a DM may be able to solve many problems long before a SWAT sniper could arrive.
