c-g-designs

Everything started around May 2004, following various discussions, directly with Laurie Ingram and a few technicians, also on the Fullbore List on the often discussed topic ‘Rear Locking Actions’.

Highly motivated on this concept, influenced also by Laurie’s enthusiasm, I decided to put on paper a principle of rear locking mechanism, sufficiently rigid to ‘shoot down in flames’  the received idea concerning the so-said myth ‘Bolt metal compression’ because of the distance Bolt Head Recess-Locking Lugs, causing cartridge case-stretching on firing.

The existing rear-locking mechanisms were studied. All references to the SMLE system were immediately discarded because of the inherent flexibility of the system and horizontal closed lugs location (contrary to all other 2 lugs systems being with vertical lugs closure).  The evaluation concerned principally Four mechanisms:

-The French MAS 1936.

-The Austrian Steyr-Mannlicher SSG 61.

-The Danish Schultz and Larsen M62.

-The Remington 788.

Numerous users of those models were contacted, and exhaustive technical exchanges allowed to conclude that the reproaches commonly made to the system were absolutely unjustified, more to the contrary...

-The French system MAS Modele 1936 was certainly the strongest, the simplest and the fastest cycling of all the military Bolt action designs. The fast cycling being mostly because of the rear locking system and lugs arrangement, allowing to reduce considerably the Bolt travel. His two generous locking lugs, situated at 45° (4.30 and 10.30 o’clock on closure) allowed exceptional mechanical performances. It was also considered that this mechanism was the basis of an extremely accurate sniper rifle, the MAS Modele FR-F1 and FR-F2, still in service to day in many armies and L.E forces.

The Austrian Steyr-Mannlicher SSG 61, bolting by means of 3 sets of lugs, similar to the interrupted threads principle, originally a sniper rifle (SSG = ScharfSchuetzenGewehr), but was also produced in limited quantities as a single shot Target version, and this model was highly considered for its Long Range accuracy.

-The Danish Schultz and Larsen M62 derived from a former repeater hunting rifle model (M.54J).The M62 was extremely rigid. This model is still highly considered by UK Match riflemen for its long range performance. This 4-Lugs mechanism represented the forefather of the SWINGs M71, PARAMOUNTs, C.G-RPAs, improved for the CG-MILLENIUMs, those models showing the same lugs geometry as the M62, but with the lugs moved at front…Thank you, Mr Larsen.

-The Remington 788  has a solid reputation for accuracy when used for the calibres it was designed for. Its multiple lugs arrangement was the real negative point for this excellent design.

I then had an evaluation made of the mechanism functions of the 3 possible variants, 2 , 3 , and 4 Lugs. arrangements.

At this stage, we had to give a name to the project, and Bill Mac Farlane ,actual Fullbore List Moderator proposed the contraction ‘C.G-INCH” who received my enthusiastic approbation.

The initial study allowed to determine several fundamental advantages inherent to a rear locking system:

-Moving the bolting lugs to the rear of the loading port allowed a considerable reduction of the Bolt travel. In a front-locking system, because of the added length of the Lugs and Counter Lugs that compels to have the cartridge to override them before being chambered adds to the necessary function stroke of the Bolt. The Rear Locking system seemed making possible to allow up to 33% of Bolt travel reduction.

-The pressure transmission to the Bolt Lugs was almost parallel to the axis of the mechanism. The rear Lugs acting much more as a buttress.

-The absence of complex shapes at the Bolt Head level allowed a perfect centering Receiver/Bolt at this important level. The close tolerances of the two diameters,  Receiver bolt reacway bore and Bolt Head diameter were moved forward significantly as compared to the Front locking system, directly at the level of the case head recess of the Bolthead. It was also making cleaning easier.

-For this important question of concentricity it immediately appeared that, contrary to the front locking Receivers, a rear locking one allowed the Receiver to be bored/reamed/threaded/squared in ONE single CNC machining operation from the front, thus allowing the perfect concentricity and alignment of all the functional bores and sguareness of thee shoulders, only obtainable for front locking in custom costly actions or by subsequent ‘trueing’, a process even more costly at the end. Effectively, a front locker need to have the  succession of bores and shoulders machined in two operations, one from the front (barrel threads and lugs recess, and one from the rear (bolt raceway).

-The system allowed a considerable increase of two important values: The Lugs bearing and Lugs shear areas.

-The cocking Ramp being behind the Lugs, the cross-sections along the Bolt cylinder were maintained perfect concentric cylinders and of ample cross-section, without any weakening point whatsoever.

-The same cause played for the Receiver, in what concerned the Trigger pocket.

-The principle was making easy the adoption of a coned breech, ensuring the feeding absolutely faultless for all kinds of ammunition, from the .223 and shorter rounds (BR or PPC), to the .338 Magnums, in a system maintained very short (187mm-7.362’).

-The gain represented by the shorter Bolt and travel allowed a substantial lengthening of the Barrel shank. I was then able to envisage a  mixed fitting, composed of two close toleranced diameters, one at front and one at rear of the central threaded part. The two diameters ensuring the centering of the barrel, and the central threaded section ensuring the only function a thread set is intended for: tighrening. (Threads are never fully self-centering). This principle being of extreme importance for frequent barrel changes, as it maintain an absolute dead zero shift.

-The system allowed also a long loading port, particularly well situated for easy feeding reach while the rifle was on shoulder.

A specification list was established with the following constraints :

-Choice of materials and treatments in accordance with the most recent metallurgy advances.

-Bolting system still quite unseen, in regular geometrical form. Two models were intended:

--The TETRA with 4 Lugs of square section, opening angle 45°.

--The DELTA with 3 Lugs of triangular section and truncated apexes, opening angle 60°.

-Length identical to the Millenium, 187mm (7.362”).

-Same Bedding system, 3 countersunk Bedding screws and compatible with the systems Flexibed and fleXibloc beddings.

-Other bedding options, recoil spigot, vee block and conventional bedding.

-Mechanism as rigid as possible. For this reason, the Receiver diameter was fixed to 38mm (1.496’) for the basic model,allowing also a larger barrel shank diameter (1.125 instead as 1.0625).

-The Bolt travel was fixed to 85mm (3.346’) this allowing direct  feeding of short and standard lenght  calibres ammunition, but also those of Magnum cartridges, up to the .338 Lapua length, but for those bigger ones, the ejection of the case only. A gain of 27% of Bolt throw travel over a normal forward locking short action,  was then achieved.

-120° cone shaped Bolt head, matching in a corresponding female cone in the barrel, ensuring a perfect smooth feeding, with no risk of bullet tips damaging.

-Symetric disposition of the Lugs arrangement, closed in triangle for the DELTA, ensuring a large section of the receiver ahead and behind of each of the Lugs, an important factor for rigidity and strength (12.00, 4.30 and 7.30 O’clock arrangement).

The first test model designed was the TETRA, built in unique prototype, that Laurie Ingram stocked using the Flexibed system in a Dunlap-style stock, chambered in 6mmBR, which he took to Canberra end of 2005 to get an 11^th place in the F-Class Championships Aggregate shooting all ranges uo to 100yards with this calibre and winning also the 2006 Daily Telegraph in the Bisley Imperial with a 88/90 score.

The designer then realised that the TETRA, with its 45° opening brought not very much improvements to his precedent 4 Lugs models and decided to realise the DELTA only, with 3 lugs in triangular shape. With its 60° Bolt opening, this model represented the perfect compromise between 4 and 2 lugs designs, with lugs bearing surfaces, lugs shear area and total added bearing angle unequalled otherwise.

Initially, Jackson Rifles were to produce the model, and some DELTA prototypes were realised under this label. Some were immediately put in use and David Richards used one in the 2008 Imperial Meeting, that he ended in the Queens Prize just one point behind the winner (shooting a C.G MILLENIUM), and with the best score at long range. David will also finish 7^th in the 2009 Bisley Grand Aggregate with the same rifle on a Flexibed stock.

Jackson Rifles having finally decided to not go further in their initial projects and, after those  prototypes, I decided to redesign the model, incorporating in it some improvements, for instance:

-Reversible Firing Pin Tip, giving the possibility to always have a spare tip inside the mechanism for a quick eventual change.

-Primary extraction ensured by the combination Bolt Stop Key / Guide ramp, extremely positive system, giving a good 2 mm of primary extraction. This was an addition to the quick  Bolt removal system.

-Firing mechanism activated indifferently by Belleville Spring Discs or Conventional Coil Spring by simple exchange of components.

-C.G- Model 22 Trigger, indifferently on 3 or 4 Levers principle to adapt to various Long Range disciplines and pull weights.

In May 2008, Chris Quartermaine,manager of Woody Engineerng, in Kattaning, West Australia and http://www.actionclear.com.au/products/cginch.php and his then partner took contact in view to obtain the fabrication and marketing rights of the INCH-Delta. We met here in Normandy, and they tested successfully two models. The serial production is well on the way now, and the rifles built on the mechanism INCH-Delta and ‘Made in Australia” start to be talked about…and to WIN… One of the first production models, Titanium Nitride-coated (very hard, low-friction Hi-Tec coating, in gold colour), met considerable success at the NRA of America Convention in Phoenix (AZ), in May 2009. It now shows in USA.

One of the first CG-Inch actions fitted in an Eliseo CG1 stock with a Broughton and Pac Nor interchangeable barrels was on extensive successful testing by Warren Dean of Thatcher (AZ), prominent member of the US F-TR Class Team. From Warren’s quote, the CG INCH is the most accurate rifle action he ever shot.

Cooperation between designer and Woody Engineering/Action Clear, now under Chris and Donna  Quartermaine management is a great human experience, and we have together several projects.

The INCH rifles equipped the South Afftican 2011 Palma Team to reach second place in the Palma, equalling the winners in VBull number. André Du Toit finished second in the Worlds Individual, winning also the U25 Worlds. 2 INCH, out of 5 C.G were in the final 10 shooters. André won the fully C.G equipped C.G rifle offered by Action Clear to the U25 winner. He came to Brisbane with one INCH and returned home with two!!.

The INCH continue to win regularily. Same week end of November 2013, the only 2 INCH shooting in the Australian ACT Centenary Queens at Canberra won each their discipline Grand Aggregate, one in Target Rifle and the second in F-Class. At the European F-Class Championships,, the CPC French Team,shooting INCHs finished second in the Rutland Team Match, close behind Great Britain and ahead of 8 other strong national treams.

Plans are now for having the INCH and its new C.G75 Tube  stock produced in South Africa by MH Arms for their home market and in cooperation with Action Clear.

We now plan extending the range to a Magnum (.338LM) repeater in Chassis/Tube configuration, followed by the short action INCH repeater, also in Tube/Chassis repeater.

R.Chombart,

28/05/2010

Revised 10/2014