Kimber's Tactical Advantage
January 03, 2011
The Advanced Tactical rifle from Kimber is ready to blow away all the myths and misconceptions that made the push-fed rifle the king of the battlefield.
It always seems to come back to the "Ford or Chevy" debate. Which is better? The Model 70 or the Model 700? Controlled-round feed or push feed? And the debates go on.
In terms of tactical rifles, the M70 found a little niche in the military sniping trades in the 1950s, but in 1966, the Marine Corps went with the Model 700 as it's official tool for clandestine precision marksmanship. The Marines designated the new rifle as the M40. Since then, the Army followed suit, replacing its accurized M14 (XM21) with a 700 called the M24, and it's been pretty much nothing but Chevys on the battlefield, or so goes the analogy. Even an overwhelming majority of the law enforcement community has adopted push-feed variants as its standard tactical rifle.
Granted, it's gained a few pounds, but 41 years and numerous overhauls later, the push-feed Model 700-based Marine sniper rifle still reigns supreme. The moniker of the latest version is the M40A3, and it boasts a McMillan A5 stock and a detachable box magazine.
|Purpose:||Target, tactical or varmint rifle|
|Action Type:||Bolt-action repeater|
|Magazine:||Five-round internal box|
|Receiver material:||4340-steel barstock|
|Barrel Length:||24 inches; tapered bull; 4140 steel|
|Rifling:||Four grooves, 1:12 LH twist|
|Sights:||None; 20-minute Picatinny rail|
|Metal Finish:||KimPro II Dark Earth; black-oxide|
|Safety:||3-position firing-pin block on bolt shroud|
|Trigger Type:||Single-stage, adjustable|
|Pull Wight:||3 pounds, 2.3 ounces (average)|
|Stock Finish:||Colored gelcoat|
|Drop At Heel:||1.6 inches|
|Drop At Comb:||0.25-1.6 inches|
|Length of Pull:||12.8-14.25 inches|
|Grip surfaces:||Deep-textured on pistol grip and forearm|
|Buttpad:||Black, high-density foam rubberSling studs/four flush cups; swivels: one swivel stud|
|Overall Length:||44 inches as tested|
|Weight, empty||10 pounds, 15 ounces|
|Accessories:||Desert tan Storm Hardigg case,manual (optional Advanced Tactical accessories kit: Leupold 3.5-10X 40mm LR/T M2 TMR IR Dark Earth scope,heavy tactical rings in Dark Earth KimPro II, torque wrench, Versa-Pod bipod, sling with quick-release swivels, cleaning kit and tactical log book; MSRP: $2,575)|
Several months prior to the InterMedia Spring Roundtable, Kimber's Dwight Van Brunt promised me the very first sample of a brand-new custom .308 Win. rifle off the company's production line, the Advanced Tactical. When the Roundtable finally came around and that beauty was handed to me, my anticipation had turned into pure giddiness and excitement, reminiscent of the day my dad threw his then-14-year-old son a set of keys to a shiny black '77 Pontiac Trans Am, telling me, "Your car's out front."
Forget Fords and Chevys, we're talking 400 cubic inches of pure Pontiac muscle now.
At the Roundtable, just as back then when Chevys were tops in my mind, I had my engrained predilections about how things should be. I admit, years of brainwashing ... errr, umm ... experience have taug
ht me that it's not a tactical rifle without push feed and a detachable box. Who am I to kid, though? While a fair portion of my time in the Marine Corps was spent with scout/snipers, I was holding a Nikon F3, not an M40A2 (the A2 was the A3's predecessor).
So I took the Advanced Tactical in hand with an open mind. Later, I'd be happy I did because this new Kimber wiped away all of my predispositions about tactical rifles.
Creating A Long-Range Warrior
The Advanced Tactical started in early 2006 as a sort of side project of Kimber engineers. Early prototypes based on the Model 84 started showing up at military and police expos about a year ago, and the law enforcement community was very receptive of the archetype rifles.
Wanting to use a slightly heavier barrel profile, engineers redesigned the rifle to utilize the thicker-walled Model 8400 receiver.
The receiver, which measures 1.355 inches in diameter, is mated to a 24-inch heavy barrel. Tapering from 1.22 inches at the receiver to 0.75 inch at the muzzle, each cold-rolled 4140-steel barrel is made and button-rifled in-house, being held to half the SAAMI minimum tolerance (plus 0.001 inch, rather than plus 0.002 of the SAAMI numbers). Each barrel is stress relieved and is given a step-down crown 0.08-inch deep with an 11-degree chamfer down to the bore.
Inside the receiver is where the real custom nature of the rifle takes shape. Most of the rifle parts are the same as those found in standard 8400 rifles, but unlike the regular production rifles, each piece on the Advanced Tactical is handfitted by a custom gunsmith at the Kimber factory. A bolt is paired to the receiver, and the dual opposed lugs are handlapped. The boltface is trued to the axis of the bore, and then the ways inside the receiver are smoothed. The chamber is finished, once again, by hand to minimum headspace dimensions.
The bolt has the familiar Mauser-style claw extractor. While the boltface is cut for true controlled-round feeding, the leading edge of the extractor is beveled to allow single loading of the chamber while bypassing the magazine. This allows the beveled claw to pop right over the rim of a .308 Win. cartridge as the bolt is closed. The bolt handle is oversized and teardrop shaped. On the cocking-piece housing is the recognizable Model 70-style three-position firing-pin-block safety.
Two thumb-wheel setscrews thread into the sleeves through the right side of the stock and anchor the cheekpiece pillars in place. The two screws are positioned low so as not to interfere with shooting from either shoulder.
A 20-minute Picatinny sight rail that's machined from steel barstock is attached to the receiver via four HD 8-40 screws. Mounted at the factory, the base adds extra rigidity to the otherwise open-top receiver. It is milled to provide more than an inch of vertical access to the magazine through the ejection port.
The standard Kimber single-stage adjustable trigger/sear unit is inletted 0.115 inch into the receiver and is attached by a flathead 3/16-inch, 32-tpi screw. The trigger is 0.36 inch wide with a smooth surface and a deep curvature.
A stout, 0.625-inch-wide trigger guard is attached to the floorplate via three hex-socket screws. When depressed, a 0.1-inch-high bump inside the front of the trigger guard releases the magazine trapdoor. A stamped magazine well fits inside a recess in the receiver and is sandwiched in place by the floorplate when the action screws are installed.
The finish on the barreled action and the sight rail is KimPro II Dark Earth. It was intentionally color-matched to the Desert Warrior (see sidebar). KimPro II is a proprietary phenolic resin that combines boron, PTFE (polytetrafluoroethylene), nano-silicates, and molybdenum disulfide. In layman's terms, it's a thermally cured, extremely durable, self-lubricating finish that has been independently tested to withstand 1,000 hours of salt spray and 1,000 hours of saltwater immersion. The finish on the bolt, bottom metal, and trigger is black oxide, which does tend to require a bit more care and lubrication.
The trigger is fully adjustable for weight of pull, overtravel, and
engagement. The latter of which can be viewed through a port in the side of the metal housing. Also note the hinged ejector (arrow).
To complete its ultimate tactical rifle, Kimber engineers decided to go with a fiberglass-laminate stock. They partnered with McMillan to create a version of the popular A5 stock that would accept the 8400 action and its unique bottom metal. Unlike the A5 used by the Marines on the M40A3, the Kimber stock has an integrated adjustable cheekpiece rather than the saddle style of the M40A3.
The stock is comprised of layered 8-ounce fiberglass cloth, which is injected with epoxy resin and compressed into an outer shell. Solid fiberglass is filled into the receiver area, and a mixture of epoxy and glass beads fill the forearm. Urethane foam fills the butt of the stock.
Two sleeves are set into the buttstock to accept the aluminum pillars attached to the adjustable cheekpiece. A pair of hex-socket screws set into the top of the cheekpiece provide for almost a quarter-inch of lateral movement either left or right of the rifle's axis. The length of pull is also adjustable via the McMillan spacer system, which is capped off with a rubber recoil pad.
Behind the barrel is a 0.23-inch-thick recoil lug that fits neatly into a recess in the 8400 receiver. With a stock attached to the rifle, one would never even know it was there.
Inset into the stock are four flush cups that accept Uncle Mike's Push Button QD 100 sling swivels. A single sling-swivel stud is securely screwed into a metal insert in the forearm. This stud is placed far forward on the flat-bottom forearm for the expressed purpose of attaching a bipod or other accessories.
McMillan molds in the desert-camouflage pattern and then tops it with a tough gelcoat. On the nearly vertical pistol grip and running down the sides of the forearm, there are deeply textured surfaces that resemble a giant's first attempt at stippling, but these rough surfaces provide for a tremendous amount of grip. Any sanding marks or surface imperfections on the stock tend to further accentuate this rifle, rather than detract from it.
The stocks are machine-inletted at the McMillan factory to accept the 8400 action, but when assembling the rifle, Kimber goes the extra step and glass beds the receiver, the lug, and a few inches of the barrel with a hand-applied skim coat.
Hand-matched to the receiver, the bolt's lugs are handlapped, and the claw extractor is beveled to allow single loading of a cartridge without using the internal magazine. The boltface is also trued to the barrel.
As a final step before accuracy testing the complete rifle at the factory, the crown is touched up by hand. Then, with a bedded and fully assembled rifle in hand, it's to the test range the Kimber engineers go to verify each and every production rifle will hold a half-inch three-shot group at 100 yards with both Federal Match 168-grain BTHP and Black Hills 175-grain BTHP--guaranteed.
Myth Busting And Paper Punching
Shortly after my T&E sample of the Advanced Tactical arrived, complete with a color-matched Leupold 3.5-10X 40mm LR/T M2 TMR IR scope, it was off to the PASA Park rifle range I went. In addition to the two types of ammunition used in the factory tests, I brought along two loads of Hornady TAP ammo with 155-grain and 110-grain bullets. But even before I started shooting my five-shot groups, my previously mentioned predispositions started to crumble.
The first to fall was the idea that you have to have a detachable box. With the large window between the Picatinny rail and the action opening, the Advanced Tactical's magazine was very accessible. It was also extremely easy to feed, which is not always the case with the tight feed lips on some detachable magazines. Further, considering the intended purpose of this rifle, it would be a really bad day for a tactical shooter who needed to fire more than one round--much less the five available in the Advanced Tactical. Having experienced unintentionally dropping a detachable magazine on more than one occasion, I began to realize that a dropped detachable box actually could be a liability in a tactical situation. Also, considering the law enforcement community's need for absolute ammo accountability, a shooter can simply pop open the magazine trapdoor and pull the bolt to the rear for a full round-count in hand.
Next to fall was the absolute need for a push-feed-style bolt because of the single-loading issue associated with Mauser-style claw extractors. With the beveled extractor on the Advanced
|Kimber Advanced Tactical Accuracy At 100 Yards|
|Factory Load||Velocity (fps)||SD (fps)||Energy (ft-lbs)||Accuracy (inches)|
|Black Hills Match 175-gr. BTHP||2588||16||2602||0.44||0.91||0.69|
|Federal GM308M 168-gr. BTHP||2582||15||2487||0.61||0.89||0.78|
|Hornady #80925 155-gr. A-Max||2791||11||2680||0.47||0.80||0.58|
|Hornady #80896 110-gr. TAP||3267||10||2607||0.46||0.65||0.55|
|NOTES: Velocity was measured at a distance of 12 feet from the muzzle. Accuracy listed is for five consecutive, five-shot groups fired from a Target Shooting, Inc., rest. Average temperature: 86 degrees. Average humidity: 62 percent. SD: Standard Deviation.|
Tactical, you simply toss a round into the action and close the bolt. Except for a slight "click" at the end of the bolt stroke as the extractor slips over the case rim, you probably won't even notice it isn't feeding out of the magazine. Since single feeding is possible, with a little manipulation to hold down the top cartridge in a loaded magazine, a sixth round can be dropped in and chambered--a 5+1 rifle.
Another interesting aspect of the Advanced Tactical is the function of the fixed ejector, which allows the shooter to eject his brass either as far or as near as he might like, depending upon the speed at which he pulls back the bolt. Generally, with a plunger-style extractor on a push-feed bolt, the best you can hope for is to catch a case as it's flung out the ejection port.
At the range, the fixed ejector proved especially helpful, as I really didn't need to police up my brass. It was all on the bench beside the rifle. So there I was, free of my misconceptions and able to concentrate solely on the task at hand: precisely firing my groups.
The extensive fitting and custom work were readily apparent during functioning, especially later during fast-action function firing. The bolt travel was smooth and tight, but it was still loose enough to prevent any kind of binding while working from the first shot to the last. The trigger on my test rifle proved very repeatable, breaking sharply at just over 3 pounds with no take up and just a hair of overtravel. It definitely helped keep every group I shot under an inch.
McMillan inlets the A5 stock for the Kimber 8400 action and bottom metal, and then Kimber follows up with a hand-applied skim-coat of bedding that extends abou
t two inches past the lug recess. This makes for a perfect union between metal and fiberglass.
As small as they were, I began to notice a bit of a pattern on the paper with several groups, primarily with the heavier loads. The rifle would fire a very tight group, and then I would find a spoiler (or sometimes two) lingering outside the main group. I knew all the screws and mounts were tight, so this continued to puzzle me until the last round was downrange, the sun was setting, and I was beginning to pack up.
I noticed that the gap on the left side of the barrel was about half the width of the right side. On closer inspection, there was just a bit of what looked like finish from the stock rubbed into the left side of the barrel. I came to the conclusion that the barrel may have been coming in contact with the stock at the moment of barrel whip, canceling out some of the harmonics, and altering the point of impact. I'd experienced this once before on a tactical rifle I had just finished assembling.
Being that my test rifle was the first one out of the Kimber factory, it left just before a new step was added to the bedding process. This involves using a temporary spacer around the barrel to equalize the amount of float while the bedding sets. This was unfortunate timing for me because I know that this rifle is capable of even better results than what I produced.
I recently talked to Sgt. Tom Campbell, a certified police sniper with the Cowley County (Kansas) Sheriff's Department, who received his rifle shortly after I got mine. He immediately took his Advanced Tactical to the range and started his two-shot-and-clean break-in process, all the while shooting five-shot groups at 100 yards.
Using Remington 168-grain Match ammo, his last three groups from his first 100 shots--remember, these were groups that were interrupted for a cleaning or two--produced 1/4-inch groups. I've asked Sgt. Campbell to post photos of his groups to the Shooting Times message board here at www.shootingtimes.com.
Campbell, who admitted to having fallen in love with the rifle, was definitely one of the lucky ones who got his order in early. Much like the Desert Warrior, demand for The Advanced Tactical has skyrocketed, and orders are outpacing production by a significant margin. I am just sorry that I have to send this one back; I've really been taken by this little hotrod. It's changed my whole outlook on bolt-action tactical rifles.