c-g-designs

^{Too often, an easy bolt lift is, for many users, a major criteria of choice for a given action.}

^{The bolt lift effort is the result of several factors that we will separately analyse.}

^{1°) The effort necessitated to rearm the compression mainspring : The mainspring must accumulate the energy necessary for the percussion. The effort necessary for its compression will then be proportional to its power .}

^{To reduce to the minimum the effort necessary, the spring rate must not increase during the said compression . The initial compression lenght (decocked position) must then be inferion to the spring maximal force lenght (L1/P1). It is the reason why the mainsprings are very long as L1/P1 is situated about 2/3 of the free lenght (L0). We will have to come back later on this subject which is a major element in the conception of a firing pin system.}

^{2°) The helix angle of the cocking ramp : Is mainly dependant of the bolt opening angle and firing pin stroke.}

^{3°) The eventual internal frictions . Those are difficult to evaluate and also dépend on the mecchanism concept.}

^{4°) The bolt handle lever lenght. and the artefact of its over-lenght is now no longer used.}

^{Necessary energy for a good percussion (SAAMI and Mil Specifications) :}

^{For a .080’ (2mm) firing pin = 64 oz/inch.}

^{For a .0624 (1,6mm) firing pin = 48oz/inch.}

^{This is determined by the fall of a 4 ounces ball falling from a given height.}

^{100¨% of a great number of primers must fire.}

^{Back to our chapters :}

^{1°) The firing pin spring : A coil spring is characterised by :}

^{Its free height = L0.}

^{Its height under its maximal load= L1.}

^{Its maximal force at L1 = P1.}

^{Its rate = ¨P/f.}

^{Its solid height = S/h. The spring force P1 does not increase between L1 and S/1.}

^{Lets take the example of a C.G firing pin spring having the following characteristics :}

^{L0= 3.5 inch (89mm).}

^{L1= 2.45inch (62mm).}

^{P1= 24.8lbs (108 N).}

^{P/f= .93lbs (4Newton).}

^{S/h= 1.85inch (47mm).}

^{To obtain a recocking without increase of the compression effort the decocked/cocked spring heights must be shorter than L1 and as far away as possible from S/h.}

^{In the case of the C .G :}

^{The spring decocked height is 2 .45 inch (62mm).}

^{The spring cocked height is 2.29inch (58mm).}

^{We are thus very far from solid height S/h of 1.85inch (47mm). This is the best condition for a long life as there is no over-compression.}

^{Developped energy is 82,2 oz/inch for a 1,6mm firing pin. By comparison, the commercial action of reference develops 73 ,2 oz/inch for a firing pin of 2mm.}

^{The attempt for some is great to replace the OEM spring by a supposed stronger aftermarket one (speedlock …etc). Those springs have then a L1 closer to L0 and does not correspond anymore to the imperatives. The bolt lift effort must then take into account the increase of the spring during the recocking (P/f) making the boltlift more difficult.}

^{2°) Helix angle of the cocking ramp :}

^{It varies under several factors,the most important being the opening angle and the percussion stroke. It must be calculated for every type of bolt. Its value is also function of the external diameter of the bolt. The ramp helix must be as reduced as possible.}

^{The ramp converts the circular opening movement into a linear movement of the firing assemblly mass.}

^{Few values ;}

1. ^{Commercial action of reference : 24°.}

^{Firing pin stroke= .245’ (6,2mm).}

^{Opening angle= 60°.}

^{Spring force= 1 8lbs = 81,5Newton.}

^{Spring force 2= 20lbs =91 Newton.}

^{Delta 59,66 and INCH = 21°.}

^{Opening angle= 60°.}

^{Firing pin stroke= .157’ (4mm).}

^{Force Bellevilles =31lbs ( 140N).}

^{Force Coil spring =24lbs (108N).}

^{C.G MILLENIUM-NZ and C.G-RPA (4lugs)= 24°.}

^{Opening angle= 50°.}

^{Firing Pin stroke .157’ (4mm.)}

^{Force BEllevilles = 31lbs (140N).}

^{Force Coil Spring = 24lbs (108N).}

^{Note A : The Belleville system delivering its energy from the free heigh (L0/P0) up to itf maximal value under maximal compression (L1/P1), there is increase during the cocking . This slightly increase the opening effort (5-6%) . But the initial acceleration and the lighter mass in motion reduce of some 11-12% the locktime.}

^{Note B : The most important source of friction during the recocking is the transforlation of the circular movement in a linear one. causing the friction of the sera against the cocking ramp and the resulting secondary frictions. The designer will have to take this into consideration.}

^{In the C.G sysytem, a roller is placed between the sera and the cocking ramp to roll against it . This eliminate friction of the sera against the cocking ramp.}

^R .G.C

^02-2020