Precision barrel making:  the Mk11 and M110

Precision barrel making: the Mk11 and M110

Posted by Charlie's Custom Clones on Dec 18th 2018

So, this is more of an update than an interesting learning article. Many of you know that we have been working on a design of replacement barrels for the Mk11 and M110 military sniper rifle. This started out of necessity as we wanted to build a few clones, and the rifle manufacturer either no longer made the barrels and / or was restricted by military contract in selling them to civilians or who knows what... they just were not available.

So, for the last year, we have been re-engineering, designing, employing experts and craftsmen and learning. I am humbled at the talent that we have brought to bear for this labor of love. And, we will have barrels for delivery in March (2018).

This is a slow process. Every week, I say... Next week...

This week was our next to final testing. We used both a KAC and an LMT bolt, and they were identical as to headspacing. I thought they might be. I dredged-up a 4 year old thread on .308 bolts, and the contributors found that LMT, KAC, LaRue, Armalite and JP all had an identical or close to perfect match. (read here) Well, I thought, viola` we are good to go. Well, my barrel engineer -- they are an odd lot, but you need them to be odd -- says, "all we really know now is that these two bolts are identical. We don't know if they are average, or thick or thin compared to others.' Shit, I said. Now what? Well, he is recommending that we individually head-space each bolt as we tighten the extensions on. 'If,' he said, 'we had a bolt drawing for a KAC or LMT, then we would know something,' which is why you don't need to head-space AR15 barrels, as there is an exact spec to build to.

That adds a little wrinkle, but if all the above bolts are the same, and we know that LMT and KAC parts are pretty much interchangeable, then I suppose I can offer the alternative of a matching LMT BCG (I have no clue if an LMT bolt will fit in a KAC carrier, but I know that either full BCG will fit in either gun, the SR25 or the 308MWS. I also can buy LMT BCGs, and then if someone chooses not to buy the BCG with the barrel, then put that one back in the lot to be head-spaced to another barrel. I am not sure what else to do.

The goal here has always been to perfectly reproduce the Mk11 and M110 barrel.

Also, I am not sure I mentioned before, but almost as hard as the barrel, has been the design and build of a Mk11 gas block. Many think the gas block is the same as the M110, and late in its life, it was, especially as the Mod 1 started to dawn in 2008 or so. But, in its first days, the Mk11 had a more solid gas block. So, we have re-manufactured the Mk11 gas block as it existed in 2001-2004. We were lucky enough to find an original deployment kit. Now, the testing on the gas block dimensions, and making sure we could attach a Mk11 suppressor, OMG !!! 

n the barrel front, we got Mr. Obermeyer to give me his entire 2nd Half of 2017 production of barrels, which averaged a little less than one per week. Yeah, a little less than one a every other week.

Mr. Barrett "Boots" Obermeyer (he asked me to call him Boots, and there IS a story there), is an incredibly talented and humble man. Boots has been a barrel maker for years, and to look inside his shop, his equipment has to be from before WWII. But that was when great machining was an art.

He took-up machining and moved into barrel making. He was an early innovator. He pioneered what is now the best rifling around, and used by Kreiger and Bartlein and others: the 5R rifling process. I understand the "R" is for Russian, but that is all I know, other than the rifling has 5 edges. He created what is now known as the Obermeyer chamber for 7.62 mm NATO rounds, and also experimented with barrel diameters, and landed on a tight chamber for the .308, reducing the barrel inner diameter by .002" to squeeze the bullet and get the 5 grooves deep into the copper for what he felt was improved accuracy. He, in fact, proved that to be the case, when using the M118LR military sniper round.

Today, the Obermeyer .308 and the Knights Armament SR25 barrels are actually tighter than other barrels. Most barrels have a .300 / .308 diameter for lands and grooves, but these two manufacturers use a .298 / .308. Seems small to you and me, but it is a hot topic of debate. In talking with Bartlein, they advised against it. It turns out that the .298 chamber size is best for the high mass bullets, like the 168 and 175 grain, but should not be used with ball ammo.

Boots gave us his entire production capacity for the last six months of last year, before suffering a stroke in late December. I spoke with his wife. He is doing well, and going to physical therapy, but has some nerve issues on the left side of his body. Boots is somewhere in his 80's I would guess, and is an inspiration to us all. Keeping up his work. The work being the love of his life, along with his wife. It was a different time in America when Boots first went to work. As I recall his story that he told me, his father owned the country store, and he worked as a child at the store. He wanted to do something different. He studied engineering, as I remember, but did not finish college. He went into military, and did some spook work in military intelligence and weapons design and communications, before starting his business. He never really retired. Sometime back in earlier years, he was a champion marksman. Many of the current barrel makers learned what they know today from Boots. It is a very tight-knit community. John Krieger learned the cut rifling process under Boots, and purchased the same Pratt & Whitney hydrolic rifling machines as surplus sometime after the War. Steve Dahlke at Criterion spent 30+ years with Krieger.

Last year, we asked him how many barrels he could make. He told us "one a week" was a good number, and we agreed on that. One day, I hope to continue to work like Boots into my 80s.

The very first barrels that Knights used in the SR25 sniper rifle and later the Mk11 Mod0, starting in late 2001 were all from Boots Obermeyer. The first were stainless in the white, then blackened stainless, and later Parkerized and Cerakoted black Chrome-Moly. I asked him how many barrels he made. He was a little evasive, but I suppose that was his G2 heritage. From some of the numbers I have seen, the Mk11 Mod 0 had a little less than 400 produced, before the Army got involved and the Mod 1 or M110 came into production. Somewhere around that point, KAC took barrel production in-house. I am not sure if any Obermeyer barrels made it into the M110. Boots told me he ramped-up production, but could not keep up with the volume that KAC needed, so it sounds like the first round of M110 barrels were Obermeyer. I personally have only seen his marks on the Mk11.

Anyway, a man and a legend. Thought I would share. I hope he can return to that shop!

When we go to production here shortly, there will be a limited run of Obermeyer barrels and also some other commercially made blanks at different price points. The M110 will probably not have the Obermeyer barrels.

We will also have a limited supply of M110 flash hiders, as well as KAC rails for both Mk11 and M110. I also have a pretty good supply of optics for those interested. I got a special military run of the M110 optic, and Mk11 Leupold is in ample supply. M110 mounts and flash hiders are still in production at KAC. Mk11 rings from KAC as well as Mk11 front flip-up sights are rare as hens teeth. I am looking at different options for the Mk11 rings that have the same look, but not the same quality. So, who knows.

Thanks for reading, and look for our barrels soon here: Charlies Mk11 and M110 barrels.