M.L. McPherson
Monday, June 23, 2003

RACE TUNING THE LEVER-ACTION RIFLE

 Synopsis:

Such alterations either increase gun rigidity, thereby improving intrinsic accuracy or smooth the action, thereby improving useful accuracy, speed and ease of use. Here, the author addresses alterations that are generally most applicable to the Marlin but each of these represents an alteration applicable to most traditional lever-action rifles of modern production (tubular magazine models produced since about 1955).

Race Tuning the Lever-Action Rifle

Considering all that must happen when the action is cycled, tubular-magazine, lever-action rifles are a miracle of simplicity. However, due to the number of articulated parts, these designs offer significant potential for action smoothing modifications. I offer these alterations, and others, as explained in the associated links, Have McPherson Tune Your Levergun, Services Offered & Order Form, in a special gunsmithing service dedicated specifically to enhancing functionality of lever-action guns. Variations of alterations addressed in this text, as required by particular gun make and model, are applicable to most traditional lever-action rifles of recent manufacture. Many readers may be familiar with, or at least may be aware of the book, Accurizing the Factory Rifle, wherein I cover all aspects of improving the lever-action rifle.

BACKGROUND

I began tinkering with guns as a child. Within a decade, such tinkering was commonplace. Perhaps my first noteworthy overhaul was on a New Model Ruger single-action, 44 Magnum, circa 1973. After tuning that to within an inch of its life, attention turned to what was then the newly reintroduced Marlin 1894, also in 44 Magnum. Over several decades and through several iterations, work on that gun included action smoothing, barrel shortening, stock and receiver modifications (to reduce weight to less than 4.6 pounds!), stock shortening, recoil pad installation, and NP3 treatment of various action parts (to further smooth operation).

CONCEPT OF WORK

It is feasible to significantly improve most lever-action rifles, as delivered from the factory, through judicious refinements and minor modifications. Tools I use include (most are available through Brownells or at a typical hardware store):

One major goal of such work is friction reduction, which improves functionality and ease of action manipulation. These alterations make it easier to load, cycle and accurately fire any such gun – specific degree of improvement depends upon model and production variables and is generally unpredictable, a priori. A second goal is to reduce stresses that result from imperfect tolerances between various parts. A third goal is to improve stock bedding: first, to reduce deleterious vibrations between barreled-action and the foreend and magazine tube assemblies; second, to increase rigidity between receiver and buttstock. A final goal is to alter spring rates, as necessary, to reduce required loading and manipulation force – specific alterations can depend upon intended application.

STOCK & MAGAZINE WORK

I begin these modifications by disassembling magazine tube and foreend from rifle. Production of a modest radius at rear outside perimeter of magazine tube is sometimes required to provide necessary tube-to-receiver clearance and prevent stress when the gun is assembled. Such clearance ensures that this tube does not bind between receiver and barrel hanger. Cold bluing of altered surface finishes this task.

Next, I apply Brownells' release agent, to receiver front, foreend cap (or barrel band) and to bottom and sides of barrel in the area between receiver and foreend tube hanger, as necessary to ensure ease of future disassembly. I install magazine tube into foreend orientated and positioned as when gun is assembled. I apply a bed of RTV (Room Temperature Vulcanizing) silicone onto top of magazine tube, where it passes through foreend. This bead should be sufficient only to accommodate formation of a layer that fully interposes tube and barrel. I then apply a thin layer of RTV to foreend at sides of tube and a more robust layer to foreend at front and rear end (where foreend enters recess in action and area that will be under foreend cap or barrel band). Noted lever-action rifle guru Keith Dehart suggested this basic process to me; I have shamelessly adapted and perhaps modified it.

When I deem it useful to reduce magazine spring tension I remove coils from this spring, according to experience and the owner's intended use of the gun. In some applications, I also reduce mass of magazine tube cap and associated components. In some applications, I alter foreend band or cap and magazine band or related parts, so that magazine tube and foreend hanger and associated parts do not generate variable stresses on barrel or create sources of accuracy-destroying sympathetic vibrations.

I install foreend, foreend cap, magazine tube, cartridge follower and spring assembly onto the properly prepared barreled action. I then apply Loctite™ to all attachment screws, installing and properly tightening those into corresponding holes. I leave this assembly alone for several hours, so that RTV can partially cure. I then peel excess RTV off.

I have perfected buttstock glass bedding, to form an intimate, rigid, enduring, and correct bond between stock and receiver, which is an important accuracy tuning feature on any such rifle. This requires sophisticated preparation so that only the correct areas are in contact. It can significantly improve the gun.

For the utmost in durability and accuracy, I add a buttstock-to-receiver throughbolt. This involves modifications to buttstock, both upper and lower tang and installation of new parts. This addition may well be the single most important improvement to any such rifle; improving accuracy and buttstock durability.

ACTION SMOOTHING

On a relatively new gun, I cycle the action several hundred times, in order to establish wear patterns. This makes it possible to determine points at which various parts are rubbing and to literally see where polishing will be beneficial. Then (after epoxy and silicone have fully cured, as necessary), I disassemble buttstock, lower tang and action.

Perhaps the easiest and most important modification is the ejector system. Due to the way this piece works on a Marlin, excess ejector spring pressure and surface roughness can dramatically increase action manipulation force; due to the way this part works on a Winchester, excess ejector spring pressure can unnecessarily increase action-manipulation force.

These spring modifications achieve great benefit, as does proper polishing of ejector and corresponding bolt surface; on a Winchester, use of lighter coil spring is sometimes beneficial, as is polishing.

I polish all bolt-to-ejector contact surfaces to reduce friction on a Marlin; similarly, on a Winchester (and clones), polishing of various friction surfaces on bolt and corresponding surfaces in receiver can dramatically reduce action manipulation force. However, I make an effort to only polish away burrs and to smooth (only) tops of high spots; further polishing is counterproductive because that can dramatically increase friction, due to associated potential increase in area of contacting surface area.

I polish various surfaces on bolt and associated parts – including some internal parts – and make minor critical adjustments to certain parts. These operations have a twofold purpose:

Particularly on Marlins, but also somewhat so on Winchesters, the finger-lever is a potential source of significant friction, due to roughness of surfaces that work against various action parts. After careful study, I have determined those areas that are most significant in this regard, along with the best means of reducing such friction to the minimum feasible. Alterations of spring rates and surface contours are important here.

I debur the lower receiver opening, to prevent roughness against the finger-lever. It is sometimes difficult to determine these areas and this is one of the more delicate tasks in this work, done correctly, this will not significantly increase tolerances but will definitely improve action smoothness.

I address problems with the hammer as I do the finger-lever, in as much as I polish all areas showing wear and debur corresponding frame areas. Additionally, I polish and slightly reshape the hammer nose, where it rides under the bolt during action opening, and the corresponding cocking ramp on the bolt, to minimize cocking force.

In a gun used solely for Cowboy Action type work and casual plinking, it is often feasible to somewhat reduce hammer spring tension, which can result in a worthwhile reduction in action manipulation force. However, I will only do this in response to your specific request because any such reduction will definitely reduce the degree of assuredness that the gun will fire each time, regardless of brand, type and production lot of primers used in a particular load ,or of variations in the care and skill with which you may have seated the primer (ignition of primers not seated fully to bottom of primer pocket always requires greater hammer force).

I have developed a simple, albeit elegant, method for adjusting hammer spring tension to useful minimum for use with factory ammunition and properly prepared handloads. This is trial-and-retrial work.

With proper sear stones and other tools, I remove high spots from trigger nose and hammer sear surface. This work requires a clear understanding of function and safety characteristics of sear. (On new Winchester brand guns, with rebounding hammer, little improvement in function or let-off is feasible.)

On the Marlin, I adjust combination trigger-return and trigger-safety-lock spring. This is a touchy project; however, when done correctly, it significantly eases action manipulation.

Similarly, I carefully adjust trigger side of this spring to provide about a one-pound force pushing trigger forward, which is sufficient for safety. On guns where owner has requested a trigger let-off force greater than about 4 pounds, I usually do not alter this spring. With rare exception, I can achieve a safe and reliable let-off between about 3 and 4 pounds on the Marlin.

On a Marlin, I polish the cartridge carrier nose; on a Winchester, I polish several parts for the same general reason. Since the carrier nose must ride past any remaining cartridges in the magazine, polishing this area can significantly smooth action manipulation.

On guns not intended for use against dangerous game, I generally modify the finger-lever latch to reduce locking force. Typically, one can open the finger-lever very easily with one finger. The trick is to achieve this and still have the finger-lever stay closed against actions of normal handling and (on the Marlin) force of cartridges in magazine that push against finger lever nose.

I will not cover here the myriad modifications required to modify these actions in order to accommodate use of cartridges that are significantly longer than SAAMI maximum specified OAL. Here I will simply note that these alterations do not compromise functionality.

Marlin 336CB 38-55 Test Rifle: Required Action Manipulation Force

Average of three tests for each measurement, all measurements approximate but relatively comparable.

NOTE 1: This measurement reflects force required in overcoming cartridge carrier ratchet. Most users who manipulate finger lever with reasonable haste will not notice this point of resistance, as inertia will carry finger-lever past this spot. Once manipulation trips this mechanism, continued force drops to <2 pounds on stock gun and nearer to 1 pound on modified gun.

NOTE 2: Loading force indicated represent minimum force required to push a round that is partially inserted into loading port deeper into port – a very difficult measurement and therefore highly subjective.

As noted in opening comments, each gun is a law unto itself and these results represent only what was achieved with basic tuning package on this particular Marlin – some guns see a greater percentage improvement with superior finished smoothness; some guns do not see this much improvement and will never work this smoothly.