The Weatherby Mark V Switch Barrel

Not all rifles are readily alterable to switch-barrel use but those that are can offer the shooter a wide range of shooting performance. As a practical switch-barrel application the set-up should be easy to work with, safe, not overly expensive to make up, and fully as accurate, or better, than the unaltered parent rifle. Where this is attained, it will likely set the stage for some interesting and enjoyable shooting.

Over an extended period spanning a couple decades, I have converted a good number of different types of rifles to switch-barrel use. This has involved more than 140 barrels and a variety of action types, chamberings, stocks, triggers, and sighting equipment.

Among those actions I have worked with are the post-1964 Model 70 Winchester, 40X Remington, Remington XP- 100, Model 700 Remington series, Savage M12 series, Stevens single barrel, Thompson/Center TCR 83, Ruger M77, and more recently, the Weatherby Mark Vaction as used for standard cartridges. The Weatherby Mark Visa somewhat lighter version of the legendary Weatherby Mark V Magnum action and the topic for this article. The bolt has six locking lugs as compared to nine on the Magnum action.

Both, however, feature a 54degree bolt lift, one of the shortest of any production rifle on the market. This Weatherby action, as used on the Super Varmint Master rifle, is a From top, a Weatherby factory stock; receiver and trigger with bolt, trigger guard and special action wrench. Third row, a Manson .243 reamer, Clymer .257 Improved reamer, Manson .22 PPC reamer, and reamer wrench.

Barrels from above area .22 PPC 1- 7 twist Broughton, .22-250 Remington 1-14 twist Criterion, .257 Improved 1-10 twist Broughton, .243 Winchester 1-10 twist Criterion; Sightron SIII 45X Target scope with Talley Picatinny mounting system. single shot and is very strong. It has a single stage trigger that is fully adjustable to a safe, crisp pull which should be performed by someone experienced in this area.

While not getting too immerged in detail, my definition of an uncomplicated, easy-to-use, switch-barrel rifle means just that. In the process of switching barrels, the scoped action remains totally undisturbed in the stock. That is to say, the barrel is removed from the action without loosening the action screws or touching the scope. The barrel is taken from beneath the scope directly through the barrel channel which is often enlarged to accommodate larger target and varmint barrels.

A special action wrench must be used to go about switching barrels while leaving the scoped action in the stock,. Where no such wrench is commercially available, it can usually be made with common machine shop tools. This was the case with the Weatherby Mark Vsingle shot action with its unique six locking lug system. As is often the case, if I can’t find a tool to do a job, I go to the drawing board and trust my visionary instincts to guide me. The Weatherby action presented a typical example of such a need.

With its three pairs

of unevenly positioned locking lugs, the Mark Vaction wrench was quite different from other action wrenches I have made. Mark V Action Wrench The action wrench was made from a semi-hardened length of rod stock and turned to fit the rifle bolt hole with sufficient length to engage the inner locking lugs and extend out within reach of the torque adapter coupling. As a pattern, I turned a wood dowel to this same diameter to get an exact impression of the unevenly spaced internal lugs.

From this pattern I marked and machined the head of the action wrench to fit the internal action lugs. I used a center cutting ball end mill to form three grooves on the end of the wrench to precisely match those of the internal action locking lugs. I then cut the action wrench to length and formed the end to fit a half-inch socket wrench drive. The socket wrench, when in place, extended just short of the front of the stock comb while avoiding contact with it.

At this juncture the main torque bar is attached using a half-inch-drive socket wrench with square drive on one end and a half-inch eight-point socket at the other. The special head of the action wrench engages the internal locking lugs and extends to a point just beyond the action tang. Here the heavy duty torque bar unites with the action wrench via the aforementioned socket wrench. From this position— with the barrel held in a special padded vise—the required torque can be manually applied to the action.

The barrel can then be easily removed or installed. Setting Up Switch Barrels Here I will provide the fundamental information on barrel installation and removal as applied to Far Shown here is the open stock with the receiver and trigger assembly below. my switch-barrel rifles. This will, however, be covered in much greater detail in a forthcoming issue of American Gunsmith. In the process of removing an ordinary rifle barrel from its action for the first time, a great deal of torque must normally be applied.

This can range well in excess of 250 foot-pounds and even more on a non-lubricated barrel joint. I normally use a special receiver-wring wrench here. The lateral friction force interfacing the barrel-to-receiver joint is termed axial preload and will vary markedly among rifle builders and rifle manufacturers. Here I will briefly describe the amount of barrel torque or axial preload that I have used in working with more than 150 precision fitted barrels to switch-barrel rifles.

I have made reference to this in my various writings but it bears repeating. Attaining optimal or desired axial preload at a barrel joint is dependent on several factors. These include major barrel thread diameter, thread pitch (threads per inch), thread lubrication (type or absence of it), as well as the condition of the

threads, barrel and receiver shoulder smoothness, and the leverage of the torque system used. I’ll not go into the details here regarding all these applied factors but will assume a good barrel thread exists and some form of lubrication is applied to the barrel threads and shoulder to assure a more uniform barrel thread and shoulder contact, as well as reducing wear at the pressure surfaces.

With a T-shaped torque bar about 20 inches long and the barrel securely held in a good barrel vise, apply about 100-120 foot pounds of torque to the action wrench coupling. If you have never used a torque wrench, perhaps you have changed a flat tire on a vehicle. The normal torque applied in hand tightening or loosening an automobile wheel lug nut would feel much the same as that applied when turning a barrel onto or removing a rifle barrel from a receiver.

I am not referring to a wheel lug nut torqued in place by a gorilla mechanic at some garages. My tests with barrel/receiver torque clearly demonstrated there is a fair amount of leeway or forgiveness in applying barrel torque in attaining sufficient or workable axial preload at the barrel/receiver juncture. I learned that torque ranging from 75-90 foot-pounds using suitable forms of lubricant work out well.

Torque application was later applied and tested on many barrels, as low as 40 foot-pounds with no significant or measurable difference in accuracy or bullet point-of-impact as compared to torque in the range of 75 to 90 foot-pounds. On several instances I have turned a barrel on hand tight, displaying groups under half-minute accuracy. I have also removed and replaced a barrel between shots, displaying equally good accuracy. But this is accomplished only with a perfect contact at the barrel to receiver joint.

Variance in barrel torque at these ranges will not significantly alter cartridge headspace and is not a significant factor. Be consistent in removal and installation of a rifle barrel for top performance. Stock Bedding Revision I viewed the Weatherby Mark V single-shot, Super Varmint Master action as a most worthy candidate for switch-barrel application. The composite factory stock has a bedding block machined from aircraft-grade 6061-T6 aluminum which augments the strength of the single-shot receiver.

This did not, however, preclude my total inspection followed by the addition of a central action screw on this three Far Center, action wrench with torque bar couples. Below, Weatherby Mark Vstandard action receiver. no-scratch, no-slip barrel jaws designed by the author are used in a vise to remove and install switch-barrels. These jaws can be used to hold and remove even the most stubborn barrels while the scoped action remains in the stock.

pound stock. This required a central brass bedding pillar and lower stock escutcheon midway between the existing front and rear action screws. A solid block of aluminum was also bonded into the existing magazine cut out. These were cast in place with Brownells Steel Bed. I then bedded all the action-to-stock surfaces with Steel Bed for a precise microscopic fit. All this resulted in one of the most solid receiver-tostock bedding contacts possible.

Stock bedding has a far greater influence on pure accuracy than is often realized. Cartridge and Barrel Selection Four barrels were chambered to the Weatherby Mark Vsingle-shot rifle over an extended period of time Barrels can be removed and replaced from beneath the scope in less than five minutes. spanning a few years. The first chambering was a .22-250 Remington, original factory, Criterion 26" 1:14 twist, varmint weight barrel. This barrel was received with the rifle.

The second barrel was a 26" Broughton R5 varmint weight in caliber .257, chambered for the .257 Ackley Improved with 40-degree shoulder. I’ve had a great deal of experience with this cartridge and despite the often maligned .257 bore, it’s a very accurate target and hunting round with good bullets. This was chambered and headspaced with a reamer from Clymer Tool (ClymerTool.com, 877/ REAMERS).

The third barrel was a Criterion (CriterionBarrels.com, 1:10 twist, 26" varmint weight barrel, chambered for the .243 Winchester. More recently, the fourth barrel is of special importance to me. It is a 1:8 twist Broughton R5 barrel from North Manufacturing Co. (Rifle-Barrels.net, chambered in 22 PPC. I used a 0.2520" neck reamer from Dave Manson Precision Reamers (MansonReamers.com, to cut and headspace the chamber.

I had a special purpose for this fasttwist .224 PPC cartridge, pitting it against the .224 Valkyrie at a later date in both long-range target work and benchrest shooting, including the use of heavier long-range bullets requiring a faster barrel twist. Threading and chambering barrels for the standard Mark V Weatherby receiver required close attention to detail. The thread shank is 0.870" in diameter with thread length of 0.890" at 18 threads per inch.

Cartridges are chambered flush with the end of the recessed barrel. The claw type extractor reaches 0.125" into the bolt recess for extraction requiring some extra attention in the barrel fitting process. Minor adjustment of the extractor was also required allowing it to latch onto the smaller 0.441" PPC case rim. Normal .30-06 and .308 cartridge rims are 0.473" so it was necessary to re-fit the extractor allowing the hook to go into the side of the bolt face about 0.020" deeper.

Scope and Mount Selection As I get into serious testing and evaluation of my shooting, anything short of high quality optics would not make the grade. There is nothing more disconcerting than to have a scope or mounting system compromise my testing efforts. For this finelooking rifle I went with a Sightron

Target shown from top left, .257 40-degree Ackley Improved with Broughton 1-10 twist barrel with two 100yard groups on left made with 87 grain Berger bullets. 300 yard group on right with 75 grain Hornady V-Max bullets. Top right, .22 PPC Broughton 1-7 twist barrel with 14 (5-shot) groups made with 52 grain bullets by Sierra, Berger, Shilen, and Nosler. Groups range from 0.225-0.425 MOA. Bottom left, .243 Winchester 1-10 twist Criterion barrel. Groups on left at 100 and 300 yards made with 70 grain Sierra bullets.

Two 100 and 300 yard groups made with Hornady 75 grain V-Max bullets. Bottom right targets from .22-250 Remington 1-14 twist Criterion barrel with 100 and 300 yard groups made with 55 grain Sierra bullets. All four barrels deliver some very impressive groups. (SightronUSA.com, SIII SS 45x45ED 30mm scope. This 30mm side focus scope has 1/10 MOA adjustment and performs with the best of them. I used the Talley mounting system for mounting the scope totally in-line and as solidly as can be mounted.

A Picatinny base for Weatherby Lightweight (six lug, No. P0025706) and Talley Signature Picatinny 30mm rings (No. TSP30M) from Talley Manufacturing (TalleyManufacturing.com, was used. Testing As each new barrel was added to the switch-barrel set-up, some pretty serious load and testing workup ensued. Case necks were outsideturned to within 0.0005" wall variance. Loaded rounds were tested at near zero runout at the bullet ogive, case neck, and case rim. After fire-forming, cases were then neck sized only.

As a result of uniform case neck preparation, bullet seating pressure is maintained to a minimum. All bullets were seated approximately 0.005" off the lands for each cartridge. Federal Gold Medal standard rifle primers were used on those handloads listed. Redding Competition handloading equipment was used in case preparation and load assembly (Redding- Reloading.com, Each rifle is somewhat different… some in many ways.

Things like trigger pull, how well the rifle conforms to the rest, and sighting equipment all come into play. The shooter is also tested throughout the process when extreme bench shooting technique must be flawless. Relatively few shooters really master the art of shooting a rifle from the bench well enough to rule out, or at least minimize, shooter error, particularly where groups hover well under half MOA.

My test routine with anew barrel invariably involves one of my well proved break-in routines, which normally begins with an alternate shoot-and-clean technique until copper fouling subsides, if present. This may involve as few as a half dozen shots to a few dozen. A well-lapped, quality barrel has invariably been easier to break in. As a note and worthy of mention, if a barrel is a poor performer during the break-in process it seldom comes through as a good shooter.

This has been borne out through the break-in process of scores of barrels that I have evaluated. It became increasingly apparent early in my testing and evaluations that the Weatherby Mark V switch-barrel was a winner. It rivals some of my better benchrest guns, particularly in .22 PPC, with many groups well under quarter MOA. Each newly adopted barrel and cartridge became anew entity with a fresh and distinct meaning. I guess this is what keeps it all so challenging and interesting for us.

But we must not take for granted how fortunate we gunsmith/writers are in having the opportunity to work with and represent those worthy products that involve this most intriguing shooting sport. The chart includes some of the tested loads representative of each of the four barrels fitted to the Weatherby Mark Vswitch barrel rifle. Space precludes a more complete listing of the many loads tested. Bullets were seated 0.005" off the lands.

Groups included fiveshot, slow-fire, under varying wind and weather conditions. Listed loads are valid only in the test barrels shown. Powder charges were reduced by 10 percent

and worked up while watching for pressure signs. The publisher cannot accept responsibility for errors in published load data. AG American Gunsmith Reader Services 1.