Chambering the Black Rifle in .308 Win. (7.62x51mm NATO) is anything but a new idea. From the early ArmaLites to the current selection of workhorse rifles on the market today, this caliber has fared well in giving the end user the extra knock-down power at extended ranges while keeping the feel, fit and function of America’s primary service rifle for well over 40 years. As mission objectives change we must adapt to the new tasks at hand, and welcome the addition of POF-USA’s C.R.O.S. (Corrosion Resistant Operating System) technology with this combat proven caliber.
All have outperformed the claims by the manufacturer and the innovation in the weapon systems continues to evolve at an amazing pace. The latest rifle in the POF-USA product line is the P-308, a larger 7.62x51mm version of their P-415 weapon system. It combines the larger caliber of the early AR-10, Knight SR-25, DPMS LR-308, Remington R-25, and others, with the piston driven operating system used in the POF rifle family.
Upgrades and Options
A quick glance at the P-308 we are testing may look like a shortened version of any of the aforementioned rifles but it takes a close look to reveal some of the details that make the P-308 stand out.
The 12.5-inch barrel is fluted to increase surface area for strength and cooling.
The POF barrel nut is several times the size of a standard barrel nut and is made of Aluminum with the intended purpose of quickly drawing heat from the chamber and barrel at a faster rate without any meaningful additional weight gain.
The new upper receiver and rail mechanism have been integrated into the latest version of what used to be referred to as the Predator Rail System. This latest design, the Modular Railed Receiver (MRR) extends completely over the gas block to the area above the charging handle providing a long, continuous Mil-Std M1913 Picatinny rail measuring over 16 inches in length, even with the tiny 12.5-inch barreled version.
The lower receiver has a heavily reinforced and deeply beveled magazine well and an ambidextrous bolt drop mechanism. With the positioning of the bolt release directly above the magazine release, the operator can empty a magazine, drop the empty magazine, insert a new magazine and drop the bolt to recharge the rifle, all without breaking the cheek-weld or taking the right hand off the pistol grip.
The POF-USA C.R.O.S. system is the same as used in the 5.56mm rifles and will serve to enhance the function, performance, durability, and duration the P-308 will function for. With little to no carbon build-up due to the piston-driven operating system, combined with the silicone nickel coating on all major moving components, the reliability factor is levels above a traditional system. The P-308 utilizes the addition of the new NP3 Finish and will eventually replace the original as the C.R.O.S. Plus.
The largest physical change may be the least visible without close inspection. The trigger group had been designed to meet the exact dimensions of all the guns in the .223 rifle series. This means all of the original existing trigger system’s components and parts are interchangeable with the POF-USA P-308. All the new adjustable triggers and even the latest drop-in trigger systems can be used with the P-308, greatly increasing the gun’s versatility.
Since the current primary operating environment for US battle rifles tends to be in hot, desert environments, the P-308 has been designed to combat the adverse effects of both heat and sand while requiring little downtime for standard maintenance when the necessity for a working rifle is the greatest.
Several factors have gone into increasing the reliability without major weight increases. The barrels are built from 4150 Mil-B-1159F Vanadium alloy with heavy machine gun fire in mind. Without sacrificing accuracy, if heavy fire is necessary the operator doesn’t need to worry about overheating or overworking the barrel as much as with a standard barrel. Optional 5R Polygonal barrels can also be purchased. These barrels are case hardened and heat treated to 70 Rockwell, twice the hardness of mil-spec and hammer forged barrels. All barrels are threaded 5/8×24 and provided with the BC-A5 muzzle brake.
The bolt carrier key is integral to the billet machined steel bolt carrier, not an “add-on” part. The bolt carrier and the bolt are heat-treated and chrome plated.
Both the upper and lower receivers are machined from 7075 T-6 aircraft aluminum alloy. The upper receiver is a Modular Railed Receiver (MRR) with a continuous monolithic top rail extending from the gas block to the charging handle. The upper receiver is coated on the interior with silicone nickel and the standard exterior finish on both receivers is black hard-coat anodized. The receiver and muzzle brake of our test rifle is finished with the Robar NP3 finish giving the receiver a non-reflective grey appearance. The black and grey combination lean more towards the “Urban Camo” style when compared to other finishes.
The POF-USA was manufactured to utilize a common .308 magazine rather than designing a new proprietary feeding device. After testing several systems, the decision was made to go back to the beginning of the big-bore black rifles and use the original ArmaLite AR-10 magazine design. This means you can use the following magazines with the P-308:
– Original (Waffle-Type) ArmaLite AR-10 magazines
– Knight SR-25 magazines
– DPMS Steel and Composite magazines
– POF-USA 25-round steel magazines
– C-Products 20-round stainless steel magazines
POF-USA Piston Operating System
Just like the POF-USA P-415 and P-416 rifle systems, the P-308 uses a gas piston mechanism instead of the direct gas impingement system. While the basic mechanism remains the same, a few parts are eliminated from the direct gas impingement system and are replaced with only three different parts to compose the piston system. The parts removed; the gas tube, the gas key and the gas rings include the parts that carry the hot gasses and excess carbon back inside the fire control mechanism and add greatly to the buildup of the material responsible for malfunction over prolonged use. With the POF-USA piston system, the gas rings are completely eliminated since they are no longer necessary for the system to function. This greatly decreases friction between the bolt and the bolt carrier making the mechanism much easier to cycle. A gas plug, gas piston and an operating rod and added and the system is complete. The gas plug has two positions: one for use with the rifle as shipped, and the second position is used in conjunction with a sound suppressor. This second position decreases the amount of gas volume used due to the additional backpressure created when using a sound suppressor. This combats excess recoil, gas blowback and an unwarranted rate of fire increase while suppressed. A simple 180-degree rotation is all that is necessary to change the gas plug position.
Two things immediately come to mind when mentioning a 12-inch barrel and rifle cartridge in the same sentence: accuracy and muzzle velocity. Both were tested on a sub-freezing day in central Maine. Since it was unlikely that the mercury would rise any higher in the following weeks, a decision was made to conduct the testing in these frigid conditions, hovering around 0° F, often falling into the negative numbers. The average temperature for all shooting was only 5° F.
Because there was over 3 feet of snow on the ground with no sign of thaw for a few more months, our standard rifle ranges could not be utilized for these tests so an improvised range was established. A portable bench was set-up and standard B-27 silhouette targets were deployed at 100 yards and 200 yards with the assistance of a Bushnell laser rangefinder.
Shooting for accuracy was the first order of the day and the P-308 system was topped with a BW Optic Y-TAC scope for this phase of testing. Targets were engaged at both 100 yards and 200 yards and 5-shot groups were recorded at each distance with 5 different types of ammo. We feel that the groups were quite “lose” compared to their real potential given the temporary range conditions and frigid temperatures. Retesting will be conducted at a later date to test this theory.
Ammo tested included Lake City M118 Special Ball 173gr. (FMJ), Federal Gold Medal 168gr. (BTHP), Wolf Gold 150gr. (SP), Remington Match 168gr. (HPBT) and Wolf Performance Ammunition 150gr. (FMJ). The tightest groups at 100 yards were fired with the Federal Gold Medal and the Remington Match. Both types gave us 4-shot groups under 1.25 inches but when the first “cold round” was factored in, the groups both measured just larger than 3 inches. Next was the Lake City with a 4-shot group of just under 1.5 inches and when factoring in the first “cold round” the 5-shot group came in at 2.85 inches. The Wolf Gold put 4 rounds in just under 2.25 inches and when adding the first “cold round” increased to 2.9 inches. The Wolf Performance Ammunition came in at 3.6 inches for the 4-round group and measured 4.25 inches when adding the initial “cold round.”