Half a century ago, boards were formed and studies commissioned to find a replacement for the .30-cal. cartridges employed in U.S. military service rifles. The goal was to develop a high-velocity, small-caliber cartridge in a lightweight rifle. Eventually, a spin-off of a successful varmint round, the .223 Rem. (5.56x45 mm NATO) cartridge, was selected, and Eugene Stoner's AR-10 rifle was re-engineered, scaled down to accept the .223 and named the AR-15. The selective-fire rifle was adopted first by the Air Force, and then by the Army and Marine Corps, and dubbed the M16. In the past few years, however, rifles chambered in .308 Win., such as the M14/M1A and AR-10 variants, have been reclaiming their place on the battlefield as special-purpose rifles for designated marksmen.
DPMS Panther Arms has been one of the manufacturers leading the resurgence of AR-10-style rifles with its Long Range 308 line. Now, in response to the need for smaller, faster and lighter carbines, DPMS has released its newest innovation, the AP4 LR-308. A compact version of the Long Range 308 rifle (April 2004, p. 66), the AP4 LR-308 is, at first glance, a ringer for its little brother, the M4 carbine. But looks can be deceiving.
Much was done to the LR-308 platform in order to trim it down. The milled billet 6061-T6 aluminum lower receiver remained the same, but the extruded 6066-T6 aluminum upper underwent a face-lift. In order to meet the requirements for the Army's Semi-Automatic Sniper System (SASS), DPMS added a brass deflector to the new generation LR-308 and incorporated the now-familiar forward assist into the backside of the brass deflector. Unlike the AR-15/M16A2 design, the AP4 LR-308 forward assist engages the flat surface on the back of the enlarged bolt carrier rather than a series of cuts milled into the side of the carrier.
A detachable A2-style rear sight (Fig. 1) was supplied on the AP4 LR-308 mounted to the receiver's top Picatinny rail. The bolt and chromed bolt carrier differ in size and design from familiar AR-15 components (Fig. 2). We installed an optional 308 Miculek Compensator (Fig. 3) for part of our testing, and it tamed perceived recoil to almost .223-like levels. Inside the LR-308 bolt, the standard single extractor spring was swapped out for a two-spring system in order to enhance reliability. Incorporating a standard six-position collapsible stock with the LR-308's longer bolt carrier required a mini buffer that measures 3/4 inches less than a standard carbine buffer.
The AP4 LR-308's barrel is of 4140 chrome-moly steel and sports a standard M4 contour beyond the front-sight assembly. Underneath the handguard, however, the barrel has a heavy profile, measuring nearly an inch in diameter.
The standard AP4 LR-308 handguard is a ribbed aluminum free-float tube, but our test rifle arrived with an optional DPMS four-rail, free-floated handguard. Due to the increased diameter of the barrel extension and the barrel nut, standard AR-15 handguards will not fit the AP4 LR-308. Also included on our test rifle was a detachable A2-style rear sight, which was attached to the Picatinny rail system on top of the upper receiver.
The fit and finish of our test rifle were exceptional. The take-down pins were remarkably tight, as was the upper-to-lower receiver fit. DPMS' Teflon finish on the hard-coat anodized aluminum was smooth and uniform, as was the chrome plating on the bolt carrier, firing pin and retaining pin.
For accuracy testing, we used a 4-16X variable scope with a fine reticle. We used three different brands of match ammunition from Federal, Hornady and Black Hills. It favored the 168-gr. Hornady AMAX Match loads, producing groups as small as 0.68 inches at 100 yards. The AP4, with its 16-inch barrel, produced an overall average of just smaller than a minute of angle (1.047 inches) with the three brands of ammunition.
Throughout the testing, we used just one 20-round magazine. It was one of the new steel magazines for the LR-308 platform from DPMS, which replaced the company's old plastic 10-round units. Throughout several hundred rounds, the AP4 LR-308 functioned reliably. Of the three malfunctions we experienced, the magazine failed to sufficiently engage the bolt stop twice when it was empty. A single stoppage was a short stroke that prevented a cartridge from being picked up. Upon opening the rifle up, the reason was obvious, the three gas rings on the bolt had aligned.
Looking at the bolt after a hard day on the range presented another surprise. We expected to see a lot of carbon build-up on the back of the bolt, as is usually the case on short-barreled AR-15s, but there really wasn't any on the AP4.
Side-by-side the AP4 LR-308 and the M4 look almost identical, but inside the AP4 LR-308 is a powerhouse. While it's not touted as a sub-m.o.a. rifle, our AP4 had the accuracy to match.