History of the M110 barrel
The M110 barrel has a long and rich heritage, beginning with the Mk11 sniper rifle system and the 5R rifling invented by Mr. Barrett "Boots" Obermeyer in the late 1990s. Our friends at Potomac Armory have started working with Boots in 2017 to create a barrel system that was both historically correct and highly accurate. What is presented here is the next evolution from the Mk11.
Boots Obermeyer had produced the original SR25 barrels in the late 1990s, and continued when the US Navy chose to cut-down the 24" barrels and make other changes to the SR25 and designed the rifle the Mk11 Mod0 in 2001 for its elite snipers in the SEALS and USMC units. Obermeyer barrels were the best at the time, and continued throughout the life of the Mk11 program, until the dawn of the Mod 1, which became the M110 for the US Army as well as the USMC.
The M110 sniper rifle system, known early on as the SASS, or semi-automatic sniper rifle system succeeded the Mk11 and become the mid-weight sniper rifle for all of the US forces in 2008. The M110 contract was awarded to Knights Armement, built upon the SR25 platform. From best we can tell, Obermeyer made all of the Mk11 barrels, and a number of the very early M110 barrels, until the production of M110 rilfes ramped-up to a pace that Obermeyer and his hand-made cut rifled barrels could not fully meet, at which time, Knights took the barrel production in-house. Knights barrels were originally Chrome-Moly-Vanadium 4150 cut rifling, following the pattern that Obermeyer set with the 5 groove patterned, which he patented, called 5R. Later, stainless was used. CMV steel is military spec, and is designed to handle extreme heat from rapid fire. CMV is considered harder to cut than stainless, so a high degree of precision is required to make a sniper barrel in CMV steel. Later M110 barrels switched to stainless, which has a shorter useful life than CMV steel, but also has better corrosion resistance and a very slight improvment in accuracy, all things being equal.
Following the initial 20" rifle, Knights refined the SR25 M110 a number of times with various 16" M110 variants that have served in battle from 2012, with some additional M110 sniper systems still being purchased into 2020.
What many people do not realize is that the modern precision long-range match barrel found in most of the best gas and bolt action rifles all trace their roots back to Boots Obermeyer. Many of the names you recognize today as the leaders in the barrel business at one point worked with or trained under Obermeyer, and many of the most accurate barrels today, including the Canadian sniper with the longest enemy kill was shot with a 5R cut riflled barrel.
Charlie's wants to thank Devon Harley, Boots Obermeyer and John Gill, who spent hundreds of hours of research, and work on this project over the last three years, and the counteless barrel experts metalurgists, engineers, designers, military historians, and manufacturing partners who made this project possible.
The Potomac M110 barrel kit
Potomac Armory has spent three years developing the best M110 barrel kit. Three years of research, design and engineering bring you the first true M110 barrel kit available on the commercial market. Our friends at Potomac Armory will be offering a number of variations of this barrel, including some Obermeyer and Knights Armament barrels, but this barrel is one that hits at the middle of the market for a match-grade sniper barrel kit.
This barrel is in carbon steel, called CMV 4150 for Chrome-Moly-Molybdium, which are the featured metals in the steel, also often found in fine knives, like Wustoff from Germany. CMV steel in 5R rifling is considered the the go-to barrel for heavy fire and accuracy. This barrel is buttoned broached 5R, which is a unique offering from Potomac, as most all button broached rifles are standard 4 or 6 groove. Also unique is Obermeyer's preferred twist of 1:11.25". Most common barrels in .308 are produced in 1:10" twist.
Contrary to popular marketing, buttoned rifling found on this barrel is far superrior in accuracy than a chrome-lined barrel or a forged barrel (CMH). Chrome lining is best for short range heavy use and dirty applications. The chrome lining aids a barrel in both corrosion resistance and internal scaring from armor piercing tipped ammo. Chrome lining and accuracy are inverserly related. the same is true of cold hammer forging. CMH is a great method to producce quality and consistently mass produced barrels. High precision barrels are either button broached, like this barrel, or cut rifling. The finest of the fine barrels are cut rifling.
For the debut M110 barrel, Potomac has chosen the button broached, which is a good compromise between very high price and solid value. Button broaching is faster to produce than single cut rifling, but provides accuracy and concentricity very close to cut rifling. Some very famous and accurate barrels, like Lilja are button broached, which other very accurate rifle barrels from Kreiger and Bartlien, for example are single cut rifling. It is common to find precision match barrels in 5R cut rifling, but this rifle is unique in providing button broached 5R, which is an exclusive for Potomac.
CMV steel in this barrel is ideal for a rapid fire military weapon, which is one reason that Obermeyer originally chose CMV steel for the Mk11 and M110 sniper rifes with semi-auto fire. The slower fire bolt guns almost exclusively use 416-R stainless steel. a CMV barrel does require cleaning and oiling to prevent rust.
Potomac will also be offering 416-R stainless barrels in 5R, which are considered to be slightly more accurate when new. The CMV barrel will have a longer barrel life. Barrel life is a relative term, since most of us will not be shooting thousands of rounds through our M110. But, it is not uncommon for police SWAT teams and Navy SEALS to have their stainless barrels replaced during the rifle's service life. The use of higher pressure rounds, like 168 and 175 grain match ammo will wear down a stainless barrel after 2,000 to 3,000 rounds, while a 4150 barrel will likey last 10,000 rounds, and withstand the etreme heat of rapid fire much better than 416-R.
This barrel is a nice fit in the middle: Superb accuracy, 5R rifling, 1;11.25 twist, .300/.308 standard groove and lands configuration. All upgrades from a standard straight groove 308 barrel. Future Potomac barrels will also have a more budget minded barrel with 4-grove 1:10 twist, and then upgrades in precision and cost to 416R stainless, .298/.300 tight fit, 5R cut rifling, and also the crown jewel: Obermeyer hand-made 416R barrels.
Not to confuse you, but this barrel will be the best seller, as it has all the necessary accuracy, longevity and historical correctness, at a price that does not break the bank.
This M110 barrel kit
The kit includes a Chrome-Moly-Vandium steel 4150 barrel, button broached in 5R rifling, with the Obermeyer 7.62 chamber. Not many people realize that Obermeyer created his own chamber for the 7.62 NATO round, and this barrel is the first civilian barrel to be chambered in 7.62 Obermeyer with an 1:11.25" twist, which was Obermeyer's specification, and found in the US Military M110 barrel. The barrel is correctly contoured to Obermeyer's M110 specifications, and will fit perfectly into an M110 or SR25 upper receiver. The original tollerances of the M110 barrel were so specific and so tight, that today, only a barrel from Knights or from Potomac will be a perfect fit. The barrel extensions are unique, and the location of the gas port on the barrel is very different from other 308-AR barrels. The barrel is threaded to accept the M110 flash hider, which is required for the M110 suppressor, which is not included.
Each barrel will be custom made, so keep that in mind, as far as timing of delivery. This is not a fast process, but we have a process that will be move with purpose to bring you the best product.
The barrel will be custom chambered and head-spaced to a matching bolt. If you have a KAC SR25 bolt, you may send that to us, and it will be serialized to match the barrel. Otherwise, an LMT bolt will be provided and simiilarly custom chambered to match the individual bolt. Charlie's has contracted with Compass Lake Engineering to chamber and head space the bolt to the barrel. For the most part, Knights and LMT bolts are interchangable, but we engage the pefectionists at Compass Lake to individually head space each barrel and bolt. If you use one of our LMT bolts, you can also buy a matching LMT 308 carrier when your barrel arrives. Both the Knights Armament SR25 bolt carrier group and the LMT 308 bolt carrier group will fit and function identically in the M110 upper receiver. As Charlie tells us, if you put them on the table, you probably could not tell the difference between the two carriers.
You can choose between a Knights Armament factory gas block, or a gas block designed and manufactuered by Potomac Armory. Either gas block is a perfect fit to the barrel, and is installed with a timing pin for the attachment of the M110 suppressor. the gas block is attached by two taper pins drilled into the bottom of the barrel and a slotted pin at the top of the barrel. The gas block accepts a mil-spec rifle gas tube, which is not included.
An SR25 style barrel nut is installed, so that the user does not need to remove the gas block to install the barrel nut. the barrel nut will match the M110 floating hand rail, made by Knights Armament.
The barrel system is finished with a proprietary taupe Cerakote color that closely matches the M110 taupe used by the US Military. What Charlie's has observed is that the barrel color is often seen as a slightly differernt color than the rail and upper receiver of the M110 rifle system. Finish is applied by a certified Cerakote technician.
Note: The barrel kit is designed to fit an M110 or SR25 upper receiver. The uniqueness of this upper receiver make this barrel a perfect fit. Other upper recievers will not be a fit for this barrel. Much has been written about potental substitutes for the Knights upper receiver. Charlie's has tested many that are commercially available, and have not found one that will fit this barrel. The M110 barrel system has very unique tollerances.
Charlie's recommends the barrel be installed by a gunsmith or KAC Armorer. The fit of the barrel to the receiver is extremely tight, and thermal fitting is recommended. The barrel nut will require a special tool to attach the barrel to the receiver and the rail to the barrel nut. It is very easy to damage the barrel nut without the correct barrel nut wrench. The attachment of the M110 flash hider will require precision timing and measurement of the overall length of the barrel from the gas block, to assure proper fit of a suppressor, if one is to be attached.
Pictured is a prototype barrel which does not have the gas block pinned and does not have the suppressor indexing pins. Some pictures show an M110 flash hider attached, which is not included. Pictures courtesy of Potomac Armory, USMC and the US Army
Note: Actual color is hard to display in studio. Expect a dull tan / taupe / FDE color.
Note: Each barrel is custom made and head-spaced to a specific bolt. Please allow 5 to 9 weeks for delivery