AR-10 Platform Primer and Adams 308 Patrol Enhanced Review

Discussion in 'Rifle Discussion' started by 3MTA3, Jan 28, 2016.

  1. 3MTA3

    Western Oregon
    Silver Supporter Silver Supporter

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    This article is intended for readers with an entry level understanding of the AR-10 platform. It covers concepts such as the difference between the AR-10 and other common defense rifles and ammunition. It also covers concepts like philosophy of use (POU) that will help you to understand the optimal way to set up any defensive rifle. As always there are no hard and fast rules. The intention for this type of information is to give the reader some basic concepts that they can apply to their own solutions.

    Some of the material that follows is based on my opinion and the opinions of others who have unknowingly made significant contributions. One of these is a former Marine Scout Sniper who used to sneak through the jungles of SE Asia. I am certain there will be readers who will take exception with some of the material as there is always an expert available who is fully prepared to split hairs. I encourage those people to write up their own article for advanced users and look forward to gaining more knowledge.

    The subject rifle and its modifications is not an inexpensive solution. It is also by far not the most expensive solution. This is a lifetime “buy once cry once” purchase I am sharing with the reader to help inform them. There are some bargains out there, but expect for your rifle to be just the beginning as you will need to account for ammunition, magazines, sights, etc..

    Disclaimers aside, let’s get on with it…

    Origins of the AR-10
    The AR-10 is a 7.62x51 NATO automatic rifle developed by Eugene Stoner of ArmaLite in the 1950’s. It was intended to be a replacement for the M1A/M14 platform. The design uses a Direct Impingement (DI) gas system that cycles the action directly with gas pressure created by the fired round. The light weight modular design features a minimum of parts, outstanding ergonomics, an improved magazine system, and recoil is in a straight line from the barrel to the operator’s shoulder making it easier to control than contemporary designs. The AR-10/AR-15 design is also inherently accurate and examples of both rifles are used in high level competitions alongside bolt action rifles.

    The original AR-10 was not a commercial success as it was not adopted by the US or its allies. Instead the US adopted the scaled down 5.56 NATO version known as the M-16, while our NATO allies adopted other 7.62x51 platforms, most notably the outstanding FN-FAL and HK-G3/HK-91 rifles.

    AR-10 Variants
    In addition to the original ArmaLite AR-10 several manufacturers make AR-10 semi-automatic designs in both piston and direct impingement. Unlike the AR-15 platform there is little or no standardization in the AR-10 world. Few parts outside of trigger groups, pistol grips, buttstocks or handguards are interchangeable between manufacturers. There has been a movement by several manufactures to standardize on the DPMS large frame pattern, but it is unlikely that the AR-10 will ever match the AR-15 in this regard.

    DPMS GII Small Frame pattern: Just as it seemed that the AR-10 world was finally standardizing on the DPMS Large Frame pattern they surprised the shooting world by developing an improved small frame AR-10 pattern they named GII (that’s a Roman numeral 2, not 11) . The GII is smaller, lighter, and due to a smaller improved bolt carrier has less recoil. Like the DPMS Large Frame patters there has been movement by other manufacturers to build GII pattern AR-10s.

    AR-10 vs AR-15 vs AK-47
    Each of these three systems is popular for good reason. They are all battle proven and reliable designs that get the job done. AR-15 vs AK has been done to death, and the tradeoffs between the two mostly cancel each other out. That said, I’ll go ahead anyway and give you my short list comparison.

    AR-15: lightweight, ergonomic, accurate, easy to modify and configure, has a much longer effective range than an AK. You can carry more rounds of ammunition than other systems due to the relatively light weight of 5.56 NATO ammunition.

    AK-47: reliable to the point of insanity, ammunition is inexpensive, and a better stopper than 5.56 at close ranges. Accuracy is adequate for close range battle. The 7.62x39 ammunition used by the AK-47 is the ballistic equivalent of the venerable Winchester 30-30 and is by far the most inexpensive of the three cartridges to shoot. Unfortunately, it also tends to use corrosive primers and typically is not capable of being reloaded due to the case material and/or primer style.

    AR-10: heavier and bulkier than the AR-15 or AK-47, but has longer range and better stopping power at any distance than the others. Due to the heavier weight of 7.62 NATO ammunition, this is probably not the system you want to lug around if you already have a 70 lb. pack to weigh you down and decide to go tromping through swamps or jungle. For homestead defense, especially with some of the newer ammunition it is an excellent choice.

    Ammunition and Weight Comparison
    The table below shows the approximate weight of 1,000 rounds of the ammunition used by the three platforms above and the relative number of cartridges that have the same weight.
    For every 4 rounds of 5.56 NATO you carry, you could also carry 3 rounds of 7.62x39 or 2 rounds of 7.62x51 NATO.

    The Adams Arms Small Frame 308 Overview: The Adams Arms 308 is based on the DPMS Small Frame pattern and uppers and lowers are fully interchangeable between the two systems. Adams Arms 308’s are designed to use standard SR-25 magazines, so MagPul , DPMS, Lancer and other AR-10 magazines will work just fine. Adams also uses MagPul MOE buttstocks and grips, though for the 308 series they use the EXOS Defense TI-7 buttstock. Handguards are either MOE or Samson EVO mid length free float. No sights are provided, however a single 20 round MagPul Gen 3 magazine comes with the rifle. Adams uses Voodoo Innovations barrels which use a melonite/nitride treatment to provide the durability and corrosion resistance of a chrome lining without changing any dimensions of the rifling. The Patrol Battle Rifle weighs 8.15 lbs without ammunition or sights. The non-free floated Enhanced Patrol Rifle with MagPul handguard weighs in at 7.8 lbs.

    All Adams Arms rifles, including the 308, are gas operated short stroke piston systems. Instead of routing the gas directly to the bolt, the gas instead pushes against a piston that then pushes the bolt back to operate it. Piston systems keep the bolt cooler and cleaner and are easier to clean, however they add a small amount of weight to the forward portion of the rifle. The heat that would have gone to the bolt in a DI system still has to go somewhere, so in a piston system it goes to the gas block instead. Don’t use plastic front sights on the gas block, and if you need to flip up a folding front sight be careful it may be quite hot.

    The limited stroke of the Adams system prevents bolt carrier group tilt and the transmission of barrel harmonics back to the bolt through the pushrod that may be present in long stroke systems

    The YouTube video below shows how both systems operate. Please keep in mind that this is provided by Adams and as such exaggerates the supposed drawbacks of the DI design:

    A final note on gas systems is that in general neither a piston nor a DI system has a significant advantage over the other. They both work extremely well, both are reliable, and both require maintenance and cleaning.

    I chose the Adams Arms 308 over other rifles for a number of factors such as the advantages of the DPMS Small Frame pattern over others, but also because of its similarity to my previous AR-15 builds that featured the Adams piston system. There are many other excellent AR-10 rifles that I considered including the S&W M&P 10 and DPMS GII Recon and MOE rifles, not to mention the ArmaLite AR-10, the rifle that started it all.

    This rifle may or may not be the best AR-10 for you just as the AR-10 may or may not be the best platform for you.


    7.62x51 NATO vs 308 Winchester: These cartridges are dimensionaly identical, but the 308 Winchester is loaded to higher pressures than its NATO counterpart. The cartridges also headspace at slightly different distances in the chamber. The Adams Arms 308 is designed for the higher pressure 308 Winchester and will operate correctly with either cartridge.

    Military Surplus Ammunition: 7.62x51 NATO military surplus ammunition such as XM-80 is abundant and reasonably inexpensive, though usually more costly than comparable 5.56 NATO ammunition. Surplus ball ammunition is a poor performer compared to newer designs, but can still be effective. It is a good choice for practice or for economic reasons.

    MK319 MOD 0 SOST/T762TNB1 130 grain Ammunition: This ammunition is greatly improved over previous ball ammunition and has improved barrier penetration and stopping power. Being slightly heavier than 7.62x39 bullets, while travelling at the same speed as 5.56 NATO ammunitions it combines the best of both worlds. The bullet construction then takes it to another level of effectiveness. This ammunition is an outstanding choice for Close Combat Battle (CQB) to medium ranges, though it is still accurate enough for longer ranges.

    This round is effectively an AK-47 sized projectile traveling at AR-15 speeds with an improved bullet design.

    A76251M1A 168 grain OTP Ammunition: This is an excellent choice for longer range defensive situations. With a higher ballistic coefficient and sectional density this round will hit much harder and penetrate deeper at longer ranges. While an improvement over XM-80C it is still limited to an 800 yard range as it goes subsonic at that distance.

    MK316 Mod 0 175 grain OTP Ammunition: This is a huge improvement over A7651M1A as it stays supersonic past 1,000 yards and has improved accuracy over a wide variety of temperature ranges. This round was reverse engineered at Sniper's Hide and the propellant was found to be 41.5 grains of IMR 4064 with calcium carbonate added for flash supression. The projectile is a 175 grain SMK, Cases and primers are Federal.

    The Rifle

    Unboxing and Initial Impressions
    The Adams Arms 308 comes packaged with the following:
    • A black cordura carry case that holds 5 spare magazines
    • A manual, a Voodo Innovations sticker, and the usual legal disclaimer pamphlet
    • A 20 round MagPul Gen 3 magazine. Some Adams 308’s came with a Lancer L7 magazine.

    The rifle itself has a beautiful fit and finish. Adams coats all surfaces except for third party parts like the Samson hand guard with a durable self lubricating coating they call Lifecoat. Lifecoat has a non-reflective satin finish and is much nicer to the touch than Parkerization or anodized metal – though that is IMO a secondary consideration in a battle rifle.

    In addition to the Samson or MagPul handguard, the Adams Arms 308 comes with a MagPul K grip and an EXO Defense L-7 buttstock. The K grip is more vertical than a standard grip and is more comfortable when using a Miculek style shooting posture with your non-dominate arm fully extended and straight. I’m going to give this grip a try, but it’s likely that it will be replaced by my favorite grip, the MagPul MIAD. The L-7 buttstock is well thought out, comfortable with a nice cheek piece, and locks solidly into place.

    As mentioned previously, the Adams 308 series is based on the DPMS GII pattern, so it feels more like an AR-15 than an AR-10. The only visual queue is that the mag well is larger than an AR-15. The Adams 308 is 70% parts compatible with an AR-15 which includes the “furniture” - pistol grips, hand guards, and buttstocks.


    This is the Adams 308 I purchased complete with scope, iron sights, and bipod. I’m planning on removing the long picatinny section from the bottom and moving the smaller one to that location for a bipod mount. There is also a sling attachment bolted to the other side.

    Iron Sights First and Foremost
    No iron sights or scope is provided with the rifle. Even though this rifle will use a scope as its primary sighting system it’s important to have a backup in case the scope is damaged or otherwise impaired. In my opinion BUIS are so important that you should buy them before you get a scope if you can’t buy both at the same time.

    There are many excellent choices for backup iron sights (BUIS) from companies like Primary Reflex, MagPul, Samson, Midwest Industries, etc., but my preference is the battle proven Troy folding sights. The Troy sights I selected are standard height with the round HK style front cover. I find that the round HK style front sight seems to align with the rear sight more quickly and naturally than other styles. Also note that there are fixed versions from most manufacturers if you prefer that style – especially useful if you don’t plan on using a scope.

    Typically, windage is adjusted at the rear sight and elevation is adjusted at the front sight. There are inexpensive tools to make adjustments, most are designed to use the tip of a bullet to depress a catch allowing you to turn the adjustment.

    Optics and Mount
    There are more choices today than ever before for optics. In fact, it’s so good it’s become difficult to decide just what to use. My suggestion is to think long and hard about how the rifle will be used before deciding not only what style of optic, what magnification, and even IF you should use an optic.

    Rifle Philosophy of Use (POU) is a term that describes how a rifle (or any other weapon) is intended to be used. POU should dictate how the rifle is set up for maximum effectiveness. POU has a distinct impact on the best choice of an optic for a rifle. The main point about POU is to avoid configuration mistakes that will prevent the rifle from functioning efficiently. Here are some basic POUs:

    Close quarters battle rifle(CQB): This rifle should be light and fast. It’s sighting system should cover 0 to 200 yards and should accommodate poor light.

    Classic Battle Rifle: Medium game cartridge, open sights, a bipod, and a berm to hide behind – what more do you need? The AR-10 was designed as a battle rifle along with the FN-FAL and HK-G3/HK-91. The hallmark of a battle rifle is that it hits hard enough to increase the complexity of your opponents protection and rugged enough to take a beating. Battle rifles are typically too heavy to be effective in QCB roles and lack the accuracy for an SPR role. That’s typically, not always…

    Special Purpose Rifle (SPR): Sometimes referred to as a Semiautomatic Precision Rifle, this rifle fits between QCB and Sniper roles and is optimized for 100 yards to hundreds of yards. The SPR should have a free floated barrel and a good trigger for improved accuracy, but still needs to be mobile enough for close combat.

    Sniper rifle: This rifle is optimized for long range shooting and usually uses a two man team consisting of a shooter and a spotter. This is a fairly heavy rifle that is a typically a bolt action, though there are some excellent semi-automatic choices.

    Here is a brief summary of different optic types starting from closest use, such as close quarters battle (CQB) and working out from there. Please keep in mind that these are only my opinions based on how I would use them.

    No optic: Sometimes it’s better to simply forgo a scope altogether. If you expect to use a rifle in self defense at the closest conditions, then a set of fixed iron sights may be the best choice. They are durable, reliable, accurate, fast, and are the lightest and most inexpensive option. Best POU fit is QCB and Battle Rifle.

    Red Dot: Red dot sights are very popular and proven optics for QCB. They are very intuitive and natural to use, and are very quick to get on target. There are good choices at all price points, though Aimpoint is the go-to choice for most shooters. The newer versions have such a long battery life that that the factory battery may be a lifetime battery. If you have astigmatism you may only see a large blurry red fuzz in the middle of the scope. Best POU fit is QCB.

    Prismatic: Prismatic sights have an etched reticle like a scope, but are illuminated. Like a red dot sight a prismatic sight will center itself on the target over a wide viewing angle. An advantage is that if the battery or electronics fail you still have an etched reticle. The main advantage of a prismatic scope that that they are not susceptible to astigmatism as are red dots and holographic scopes, and always present a crisp clear image. I have used and can recommend Vortex Spitfire prismatic scopes as being effective, rugged, and easy to use. Best POU fit is QCB.

    Holographic: Holographic sights have an open field of view and are probably the quickest of all the electronic sight options. The disadvantages are cost and the large exposed reticle can easily be obscured by rain, mud, or snow. As with red dot sights, if you have astigmatism you may only see an large blurry blob. Best POU fit is QCB.

    Fixed Scopes: Fixed scopes have and continue to be used in military applications with great success. Fixed scopes are very rugged, relatively light weight, and at the same price point have superior optics to variable scopes. The inexpensive SWFA Super Sniper series are battle proven scopes that offer first tier optical quality at a budget price. Best POU fit is Sniper.

    Variable Scopes: Variable scopes bring versatility at the expense of cost, weight, and complexity. There are excellent choices at all price points, but you do get what you pay for. Pay careful attention to your intended use, AKA, philosophy of use (POU) or it is very easy to mismatch rifle and scope. Best POU fit is SPR and Sniper.

    The POU for my Adams 308 is Special Purpose Rifle (SPR), so it needs the versatility of a variable scope. Since the range for an SPR is as close as a few yards to hundreds of yards the scope needs to have a fairly low magnification at the bottom end to allow for field of view while having reasonably high magnification at the high end to shoot to say 600 or so yards. Therefore, a medium range variable scope is the most appropriate range.

    In addition, an SPR needs to be fairly mobile, so the scope needs to be light and durable without compromising optical quality. The reticle needs to be heavy enough to quickly acquire a target while at the same time fine enough to allow for accurate shooting. The scope must also be bright enough to accommodate low light conditions.

    Taking the above into account I selected the Leupold VX-R 3x9 Patrol scope. This is Leupold’s entry level value tactical scope. The primary difference between it and its non-tactical hunting version is the reticle, exposed turrets, and matte finish sans the Leupold signature gold ring.

    The VX-R series scopes also feature a variably illuminated red dot at the cross hairs to aid in low light conditions. The reticle is based on the standard mil dot design. While having excellent optical quality this scope is also very light at 15.3 oz/433.7g.


    Scope Mount
    There are almost as many ways to mount a scope as there are scopes. I selected the Nikon M-223 XR 30mm mount because it provides a very solid base with minimum weight. Like other mounts designed for the AR platform it will allow co-witnessing with standard height iron sights. While it isn’t as convenient as a quick detach scope mount it is still fairly quick to remove. It also lacks the bulk and projections of most clamp type scope mounts. It also features a built in 20 MOA adjustment.

    The factory trigger is a standard mil spec combat trigger, meaning it is reliable and gets the job done, but is a bit heavy and rough for long range work. After looking over the vast array of available AR-15 triggers I selected the Giessele SSA-E . This is a two stage trigger designed for both long and short range combat. The pull weight of both stages is designed for stressful situations while allowing for reasonable accuracy. It is also very crisp, but intentionally not as crisp as a match grade trigger.

    All Adams 308 models come with a very effective compensator they claim reduces recoil by 85%. While this is wonderful, nothing comes without a price. Compensators are LOUD to the point of having flash bang like effects on a 7.62x51mm rifle. If you have the option of hearing protection this is not a problem, but in a defensive situation you may not have the opportunity to use them.

    The second issue is that compensators are rarely good at hiding muzzle flash. The supplied VDI Jet Comp will be replaced by a Smith Vortex 1000V. See the YouTube video for a demonstration of the Smith Vortex at night:

    Range Test
    Now we get down to the nitty gritty. We need to know that the rifle is reliable and then how well does it perform. The range test is pending, but has two parts:

    Break In and Reliability: This portion consists of firing 200 rounds of XM80C ball ammunition I picked up on sale recently. The first 40 rounds will be fired at a slow pace and remaining rounds will be fired at in increased pace to stress the system and break it in. This will likely be a reactive shooting situation where accuracy is not the goal.

    Accuracy Testing: This test will be done with factory loaded match grade ammunition. Adams guarantees less than 1 MOA accuracy from this rifle for life. This will be done from a bench rest using sand bags for support.

    Spent brass will be reloaded with 130gr MK319 MOD 0 SOST bullets I got inexpensively on a closeout surplus sale.

    I will provide a report on this rifle once the range test has been completed.

    Manufacturer Links
    Adams 308 Patrol Enhanced: Adams Arms Small Frame .308 - Patrol Battle Rifle
    Troy folding front sights: Front | Troy Industries
    Troy folding rear sights: Rear | Troy Industries
    Leupold VX-R Patrol 3x9 scope: Leupold Optics VX•R Patrol 3-9x40mm (30mm) -
    Nikon M-223 XR scope mount: M-223 XR Mount from Nikon
    Giessele SSA-E trigger: Super Semi-Automatic Enhanced (SSA-E) Trigger
    Smith Vortex 30 caliber flash suppressors: 7.62mmm/.30 cal. Vortex® Flash Suppressor / Eliminators : Smith Enterprise, Inc.

    AR-10 - Wikipedia, the free encyclopedia
    AR-15 - Wikipedia, the free encyclopedia
    Federal T762TNB1 ammo review and the road to a clone. Pic heavy - M14 Forum
    MK 316 MOD 0 propellant? Found
    What is Lifecoat? - FAQ
    Close combat - Wikipedia, the free encyclopedia
    Battle rifle - Wikipedia, the free encyclopedia
    Mk 12 Special Purpose Rifle - Wikipedia, the free encyclopedia
    Sniper rifle - Wikipedia, the free encyclopedia




  2. etrain16

    Silver Supporter Silver Supporter Bronze Supporter 2017 Volunteer

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    Nice :) Glad to see you posted this. Very informative!
    3MTA3 likes this.
  3. Boboclown

    North Carolina
    Bronze Supporter Bronze Supporter

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    Good post. Not going to lie though, I only skimmed through it. I like that you decided to post a general background for the AR-10 though.
  4. Lance Jacobs

    Lance Jacobs
    South Willamette Valley Oregon
    Well-Known Member

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    I am really confused at this point about your rifle. o_O

    The photo that you have posted here exactly matches photos on the Adams website for the free-floated Patrol Battle Rifle, not the Patrol Enhanced non free-floated model.

    I cannot figure out how to reconcile this discrepancy. It would seem to me that you have purchased the more expensive Patrol Battle Rifle, and not the less expensive Patrol Enhanced model.

    I am also a big fan of the Leupold VX-R series scopes. They are indeed a great choice for an AR rifle that does not break the bank. Although I went with a slightly smaller and lighter 2-7x model on my 308 AR.
    Last edited: Jan 29, 2016
    3MTA3 likes this.
  5. Sgt Nambu

    Sgt Nambu
    PDX OR
    Member Emeritus Silver Supporter

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    Great write up! Learned something's!:)
    etrain16 and 3MTA3 like this.
  6. Don H

    Don H
    Well-Known Member

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    Great article! Thanks!
    etrain16 and 3MTA3 like this.
  7. 3MTA3

    Western Oregon
    Silver Supporter Silver Supporter

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    You are correct - my rifle is the free floated battle rifle. I somehow got the names backwards. Ill see if I can get a moderator to change the title.

    I'm a huge fan of 2x7 scopes - hard to beat for price, weight, size, and effectiveness - usually my go-to scope for just about anything. It was the turrets, reticle, ARD compatibility, and matte finish of the scope I chose that led me to the 3x9.
    Sgt Nambu and etrain16 like this.

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