c-g-designs

                             ACTION DESIGN.

  II)-CONCEPTION OF SINGLE SHOT  MATCH ACTIONS

2-CUSTOM vs COMMERCIAL.

What I would consider is that there is actions and actions, first, the single shot target models, who will be my main subject here, and repeaters. Even in the single shot category, there is divisions, as, for instance,  Bench Rest actions are not perfectly suited for prone shooting, and vice-versa. They can do, they can be rather well implemented to better suit, but with limitations and eventually adaptation….And now comes the F-Classes, for which more specifications and requirements will soon appear; such as, for instance, the ability to hold long, heavy barrels.

I will only mention the repeaters to say that I have difficulty to imagine their full ability to hold our actual LR Target, Match and F-Class 30" + long heavy barrels, whatever the bedding system in which they seat, due to their reduced and complicated cross sections with multiple wide openings. They usually do not appear on top of major Long Range competitions results lists…

A general consideration about custom single shot actions is that, despite their relative limited number as compared to commercials, they have contributed to win much more prone LR,F-Class and BR competitions  than all the others altogether.

A commercial action is conceived from the start in terms of economics, and this start for example with the raw material, selected primarily for its machine-ability and lower cost. There is already a slight structural difference between a standard 4140 (42CrMo4) and a 4140+S steels, the  lower characteristics free-machining variant but also the most used for mass production receivers. Customs most of the time uses more advanced materials and treatments.

I have nothing to comment about the principle of trueing a mass-produced action, other than mentioning re-cutting the threads reduces the Receiver cross-section at front,  modify and place out-standards and out of tolerances the barrel shank length and thread diameter and also sear and primary extraction timings.. This operation places the action out of  manufacturer’s standards, and that has to be borne in mind all the action’s lifetime, at each barrel change, considering also the second-hand acquired actions who could have been ‘treated’ that way by the former owner. When changing barrel, this will be each time a problem. This makes re-barreling more complicated and asks for precise measurements prior to any attempt.

Re-cutting or even simply lapping receiver and bolt lugs bearing surfaces can also impair the good timing of an action, and need to be carried with care. Customs does not  need that, or it had been performed during final assembling at the factory and provision was then made for that to maintain the dimension specifications .

I also agree with the firing pin tip diameter reduction to .0625’ (1,60mm), a C.G concept from always, now a feature of most customs, although I think in the case of a transformation (bushing), the complete Firing Pin system should be re-designed, and, perhaps a better material and treatment used for the F.P , also reshaping for a moving mass reduction as, if  a design was intended for the larger tip section (.080" / 2mm), it might be less adapted for the smaller diameter. A .0625’ F.P tip requires more than 1/3 LESS impact energy than a .0800’ one to perform a perfect ignition. Reducing mass in motion and adapting the spring will reduce locktime and in some cases allow a lighter trigger pull weight and a lighter bolt lift. In fact, the transformation to .0625’ should led to a complete re-thought of the firing system….

Now, on the single shot actions adaptation to the disciplines:

--1°-

Purpose-designed single shot actions can be and usually are, shorter than repeaters (the single-shot variant of a repeater model cannot be considered as a true single shot as it also have the same longer receiver and bolt), with for the purpose-designed Match action having the loading port much more rearwards at better reach when on prone position than on a repeater or an action primarily designed as a repeater, who need to have the trigger mechanism placed behind a magazine well , this consequently moving the loading port too much forward for a good single loading reach, and those imperatives does not apply to single shots who can have then the trigger moved much forward, resulting in a shorter receiver and bolt . Also, single shot receivers cross sections are stiffer all the way long (no magazine well and smaller port). On a repeater, the port is intended as an EJECTION one and its each for loading is not as important, while on a true single shot Match action it is primarily a LOADING port.. and often the fired case is even collected by hand and, in this case, easy reach while in position is much appreciable.

--2°-

The single shot actions can be perfectly adapted to the discipline, just give 2  examples:

A)

-Feeding, bolt rotation and locktime:

          ----For a BR action, important is fast feeding, easy bolt lift. The locktime is secondary, as the rifle is steady on rests when fired. For easy bolt lift, the 90° rotation of the 2 lugs designs is the majority, and the firing system can be calculated as to also help re-cocking, and to allow featherweight trigger pulls.

          ---In the case of  a prone rifle shooting, the reloading must be made with the less possible disturbance in the shooter’s position. For this, 60° or even 45° bolt openings are considered, as well as fast locktimes. In to-day’s concepts, it is probably the 3-lugs-60° opening who will be prevailing.

          ---The reduced bolt rotation places also the handle at better reach, with no interference with the hand at grip when closed or scope or rearsight on opening.

--There is a certain tendancy  for BR to have dual-ported receivers, this ensuring a faster feeding. This is also excellent for a rested rifle, but I think this is not recommendable (even eventually useless) for prone shooting, as I would not recommend this second port just in front of the shooter’s face when in position, not mentioning an extra orifice for rain and foreign corps entry…and also the resulting cross section and stiffness reduction.

B)- Triggers

:

--BR shooters favor featherweight direct pull (single-stage) triggers. As a consequence, the locktime is increased, as the FP needed energy is acquired more by increasing the FP travel and eventually  mass in motion than by spring force, hence the longer FP travels and heavy FPs. The lighter spring force also helps significantly in obtaining a lighter trigger pull.

---For prone shooting, more and more shooters use the two-stage triggers, effectively having a slightly heavier first pull, but a final pull  (Second stage) comparable to the pull of a lightweight Single Stage one. This slightly heavier trigger control is also often one of the consequences of shorter FP travels and  stronger FP springs.

This is my point only. I just wanted to say the Do-It-All action does not really exists. The subject is much too vast for such a writing, and sorry if it is boring or controversial for some. I also know it is far to be exhaustive..

The barrel and chamber are VERY important parts of Match  firearms accuracy. True, but there is much more technology, adaptability and ways of improved accuracy in the match action than in the barrel.

I would also not ignore the part taken by stocks, bedding and sights in the equation. ….Not also ammunition, components and reloading techniques, but let’s stay in the subject.

R.G.C