A POWERHOUSE IN A PDW-SIZE PACKAGE

Chambering the Black Rifle in .308 Win. (7.62x51mm NATO) is anything but a new idea. From the early ArmaLite’s 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.

pof trigger

The fire control group has been designed to the exact specifications of a standard AR-15/M16/M4 allowing the user to utilize any of the numerous upgraded trigger systems available for that popular weapon system

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.

Built Tough

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.

The POF-USA BC-A5 muzzle device. The contact points give it a unique look and aid in functions such as breaking glass while lessening the possibility of damaging the end of the barrel

The POF-USA BC-A5 muzzle device. The contact points give it a unique look and aid in functions such as breaking glass while lessening the possibility of damaging the end of the barrel

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.

Magazine Compatibility

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
– PMAGs

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.

pof rifle

Full left-side view of the POF-USA P-308. This .308 powerhouse is small enough to be used is tight quarters but still provides the ability to be effective at long distances if necessary

Trigger Time

Two things immediately come to mind when mentioning a 12-inch barrel and rifle cartridge in the same sentence: accuracy and muzzle velocity. For the purpose of the data collected in this article, both were tested on a sub-freezing day in central Maine. (The video was shot 09/10/13) 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.

Accuracy Testing

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.”
Testing was duplicated at 200 yards with the following results; (Since we explained the “cold round” effect in the last paragraph but don’t have enough solid data to know exactly how much difference it makes and how repeatable it is we will just report on the 5-shot group measurement this time). Wolf Performance Ammunition measured 3.4 inches, Wolf Gold grouped at 3.5 inches, Lake City was 3.6 inches, Federal Gold Medal measured 3.7 inches and the Remington Match came in at 4.1 inches.

pof 308 rifle

Right side photo of the P-308 lower receiver clearly illustrates the ambidextrous selector switch (A), the ambidextrous bolt release (B) and the oversized trigger guard, which is a machined part of the receiver and not an accessory. The magazine release (C) is completely shielded by the receiver making it unlikely to be depressed unintentionally

Once again, it can’t be stressed enough that the above numbers were recorded in less than ideal conditions. Shooting in sub-freezing temperatures, while wearing bulky clothing and walking through thigh-deep snow to tend targets will produce much different results than shooting on a covered range in the summer months. We hope these results may be valuable to those who work in these very cold environments and we also hope they are not directly compared to test results acquired in a controlled climate because they will not be equal.

Muzzle Velocity

The same ammunition used in the accuracy testing was also used to measure the muzzle velocity. The barrel of the test gun is a 12-inch barrel, rifled 1 turn in 10 inches and utilized a POF-USA BC-A5 muzzle brake. Since it was getting into a fairly low light situation in the last afternoon we had the opportunity to evaluate the ammo for visible flash. We found that the Wolf Performance Ammunition had the most flash, several times more than the others, and the Remington Match ammunition was a very distant second. We didn’t do any shooting without the muzzle brake but by the absence of any major flash in the other loads we can assume it was effective. The muzzle rise seemed minimal but the noise was quite noticeable. This brake combined with such a short barrel produced a sharp noise noticed by all shooters.

Due to the low lighting, a PACT MK IV XP Championship Timer & Chronograph was used in conjunction with the latest M6 Infrared Skyscreen kit. These screens use infrared lights and reflectors creating an accurate and useful “beam” for use in any lighting condition. At the time we finished the testing this day it was so dark it was difficult to see the impact area through the scope and the data just continued to roll in as though it was done in bright light. All measurements were recorded at 8 feet from the muzzle with an average temperature of 5° F.

The highest average muzzle velocity (MV) was recorded shooting the Wolf Performance Ammunition at 2,335 fps. It was followed by the Lake City M118 Special Ball at 2,239 fps, the Federal Gold Medal at 2,225 fps, the Wolf Gold at 2,221 fps and the Remington Match at 2,202 fps.

Almost all ammo was very consistent with the extreme spread over 5-shot strings recorded as follows: Wolf Gold – 29 fps, Wolf Performance Ammunition – 36 fps, Federal Gold Medal – 50 fps, Remington Match – 54 fps and Lake City M118 Special Ball – 130 fps.

Fit, Finish and Function

From first handling, it is apparent that the P-308 is manufactured with quality in mind. Everything is tight and solid. Frank DeSomma, CEO of POF-USA, has been prioritizing quality over quantity as long as this writer can remember and the P-308 is no exception. The details are in the “extras” that are available with the constantly evolving POF-USA product line. Some of these enhancements would include the machined, enlarged trigger guard over less expensive “snap-in” guards, and the ambidextrous bolt drop, designed and included at a significant additional production cost. The POF-USA “heat-sink” barrel nut is another example of using superior products in the production process rather than using less expensive, less effective parts that are readily available.

The finish on this particular rifle is the Robar NP3 Electroless Nickel on the receiver and the muzzle brake. The finish is extremely hard and resistant to corrosion and used in the Aerospace industry. The rail system is hard-coat anodized and the interior of the upper receiver, the charging handle, the bolt and carrier are all coated using the C.R.O.S. Plus system.

pof 308 bolt carrier

The components of the P-308 gas piston system: the gas plug, gas piston, push rod and bolt carrier. Note the lightning cuts in the solid-machined bolt carrier to reduce weight while retaining strength

The function of the P-308 will not disappoint. We found no particular ammo it didn’t like and the adjustable gas plug is quickly rotated and positioned for suppressor use or heavy ammo. The short barrel on this particular test rifle provides a little more muzzle blast than one may be accustomed too but if you are a “short barreled rifle person” that is part of the allure. A little heavier than the much smaller P-415, it is also a heavyweight in performance making the additional weight a fair trade.

American Made

In these days of outsourcing for cheap parts and/or labor, you have to be cautious about the wording of manufacturing claims. “Assembled in the USA” usually has underlying meanings, as do several other tricky slogans. When we asked Frank DeSomma about his “Made in the USA” claim, he couldn’t have been clearer and he proudly reiterates the following to anyone who will ask and on his website:

All raw materials are manufactured from US Steel Mills.
All heat treats, plating/coatings, are completed by U.S.A. owned and operated manufacturers.
All accessory and component parts on our weapons systems are from U.S.A. owned and operated manufacturers.
All POF-USA weapon systems are 100% pure American made.

Field Strip

The POF-USA P-308 disassembles exactly like the P-415 and P-416 5.56x45mm variants. The lower receiver is no different than the AR-15/M16/M4 family of firearms with the exception of the addition of the ambidextrous bolt release on the right side of the lower receiver. No tools are necessary to perform this procedure. Remove the magazine and make sure the firearm is unloaded by visually checking the chamber. Close the bolt carrier by depressing the bolt release. From the left side of the gun push both receiver pins to the right, through the receiver and pull them to the right until they stop. Remove the upper receiver from the lower receiver by lifting strait off. Gently pull the charging handle rearward and remove the bolt carrier from the rear. When the charging handle is all the way to the rear lower it inside the upper receiver to disengage it from the slot it rides in and remove from the rear. Depress the spring-loaded push pin on the gas plug and rotate the gas plug clockwise 45 degrees. (If the gas plug turns hard you can use the base of a .308 cartridge to assist it by inserting the rim into the gas plug groove.) Remove the gas plug by pulling to the front. Lower the muzzle and the gas piston, followed by the op-rod will slide out the hole opened by removing the gas plug. The rifle is field stripped and most cleaning and maintenance can be performed at this point. Reassemble the rifle in the reverse order.

Compatibility

While doing research for the P-308 article an item came to our attention that allows the weapon system to be even a little more universal. Cold War Shooters sells a pin sleeve that makes the POF-USA P-308 lower receiver compatible with the DPMS and Fulton .308 upper receivers. The sleeve is $19.50 and the model is simply: “POF.308Sleeve”. Their website is: www.coldwarshoters.net.

Conclusion

The small package of a PDW with the knockdown power and distance capabilities of a much larger rifle is a homerun. Redesigning the lower receiver to accept all standard AR-15 trigger parts is a great leap forward due to the number of extremely high-quality aftermarket accessories available. Even though we didn’t get the opportunity as of this writing to spend any meaningful time with this system as a suppressed platform, we have plans for it in the near future. Longer barrels are not always a good combination with subsonic ammunition due to increased friction over a longer surface area. We are thinking that this 12-inch barrel combined with a sound suppressor and a quality subsonic load may have some serious applications, especially when combined with the adjustable gas plug and a scope designed for multiple aiming points. Even though we have several ideas for future testing that we have not had time to complete yet, on our initial evaluation the POF-USA P-308 has all the earmarks of a winner.

The P-308 is available with a 14.5-inch barrel and permanently attached brake (bringing the legal barrel length to over 16 inches), a 16.5-inch barrel and even a 20-inch barrel if you would rather stay with a regular Title I firearm. Regardless of your preferred barrel length, if you decide you would like to make the transition to a .308 in the familiar Black Rifle platform, you will not be disappointed with a P-308. To be completely fair, you may have just stumbled onto a new obsession.

Specifications (as tested)
Caliber: .308 Win. (7.62x51mm NATO)
Weight: 8 lbs, 11 oz
Overall length: 30.5 inches
Barrel length: 12 inches
Barrel Material: 4150 Mil-B-1159F Vanadium Alloy
Rifling: 6-grove, 1 in 10 inches
Lower receiver: Billet machined 7075 T-6 aluminum
Upper receiver: Modular railed receiver 7075 T-6 aluminum
Trigger: 4-pound single-stage Timney drop-in group
Stock: Vltor 6-position collapsible
Finish: Robar NP3 electroless nickel

 

Jeff

Jeff is a long time veteran of the gun writing world. He's a well known writer who is featured in publications such as Small Arms Review, Small Arms Defense Journal, The American Rifleman and specialty magazines for Harris Publications. Jeff has access to one of the most exotic weapons collections in the U.S. and is one of the foremost experts in the realm of small arms.

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  • Tom – UK

    Hi guys just a small request. In future when stating ammo brands and the groupings achieved could you write them in a list format rather than a aragraph as it makes it much easier to read. eg.

    Grouping at 100m

    1. Ammo A – 2 Inches
    2. Ammo B – 4 Inches
    3. Ammo A – 1.5 Inches
    4. Ammo A – 2.5 Inches

    • Jeff

      Great suggestion. Thanks!

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  • Not Jimbo

    It’s freezing in September!? I’m confused ….

    • Jeff

      The video was just done but the data for the article was compiled during a winter shooting session. It should have been clear in the article but I’ll go back and check in case it was left out. Because the video brought so many questions about performance that we didn’t have time to cover in a short space, we brought out the full T&E from an earlier time. Thanks.

  • http://gravatar.com/skeld1 Skeld1

    I didn’t think that the Armalite magazines and the SR-25/DPMS magazines were the same. Don’t PMAGs only fit in LR-308 compatible weapons?

    • http://www.bigshooterist.com Jeff

      The original waffle ArmaLite magazines are not the same as the current ArmaLite magazines. All the above are interchangeable, as indicated.

    • Max

      ArmaLite meaning original ArmaLite. The current company calling themselves “ArmaLite” is not the same company that developed the AR-10, AR-15, AR-18…. they just own the name now. The current “ArmaLite” uses modified M1A magazines, I believe. SR-25 magazines are based off of the original ArmaLite waffle mags(the first SR-25 mags were actually waffle mags), and of course, PMAGS are meant to be an analogue to those. Military use + magpul producing them = standardization is imminent/resistance is futile. Lots of companies offer their proprietary magazines in hopes of capturing the market like the AR-15’s mag did with 5.56length chamberings, but that ship sailed a long time ago when the original AR-10 came out with a modern style straight-in magazine.

  • http://gravatar.com/vothmr vothmr

    I fail to see the point of these super short barrels in full rifle caliber. If you want to use a .308 then use a proper length barrel. 2200 fps? whats the point. all the kick and no extra power for it. And sub sonic loads? are even worse. The rifle looks nice but I do not see a value in the concept.

  • Jeff

    That’s the beauty of living where we live vothmr, something you see a “pointless” and I find as “useful” can coexist. There are several roles that SBRs fit in my world but if they don’t work for you, you can buy all the full length guns you like. Ain’t it great? – Jeff