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Double Rifle Action Strengths Compared, Respected French Paul Demas designed Verney- Carron, compared to less respected Italian Sabatti

French Paul Demas designed Verney-Carron Actions:
The Standard Directory of Proof Marks says “France joined the rest of the proof countries at the International Proof Conference in 1914, and the French proof mark is held equal to those of other countries where proof is compulsory.” In France, “proof of rifled barrels is accomplished by firing a proof load which produces an excess pressure of 30% over the normal pressure.” “Normal pressure,” usually called “service pressure” is defined as an average of the normal factory loaded pressures for specific caliber cartridges. In the 1920s, “the exploitation of high pressure as a means of advertising became widespread in France,” says the Directory, and continues somewhat to this day, with literature from the Paul Demas designed Verney-Carron Azur side by side double barreled rifle advertising boasting their “fine receivers that absorb very high pressure levels of 5,700 BAR” (the 5,700 BAR pressure was from a proof load; not from a normal service factory load, so it was 30% higher than the highest average pressure factory loaded cartridge normally chambered in this rifle, the service load). Part of the reason for this ability to absorb such a high pressure proof load, was due to their actions being made from a modern high tensile strength alloy steel, 35 NCD 16 steel. 35 NCD 16 is a French designation for this steel; it is among the highest strength, toughest steel available in the world today, with similar strength and characteristics to the American S7 super steel with. The Paul Demas designed Verney-Carron boxlock actions are a modified, improved, version of the French Chapuis action design, as Paul Demas originally worked with Chapuis before leaving that firm to begin his own firm, eventually becoming Verney-Carron, so he early on was intimately familiar with the Chapuis design. Both the Chapuis and the Paul Demas designed Verney-Carron are radically different from the more traditional action designs begun originally by the British, which have a central lump with single point hinge pin contact, and a single recoil surface on that lump. The Chapuis, on the other hand, has two point hinge pin contact with no recoil surface on lump, so barrels are sandwiched between a single wide locking bolt, while the Verney-Carron has three point hinge pin contact with a triple recoil surface, thus the Verney-Carron has three lumps in a row on underside of monoblock. Both of these French systems use a single wide under bolt, with the Verney-Carron version being 24 mm wide by 6 mm thick. The Verney-Carron uses monoblock barrel construction, which imparts good strength.

Italian Sabatti :
The Sabatti model 92SF big bore double rifle, chambered in various calibers, with all calibers using one action size and style of a traditionally designed, robust side bolstered boxlock, bolted by a traditional Purdey type top lever activated underbolt 16 mm wide by 6 mm thick, the same thickness as used on the French Verney-Carron. These Sabatti actions are also made from a tough, modern high tensile strength tri-alloy steel comparable with the strength and specifications of the French 35 NCD 16 steel and with the American S7 steel. They use monoblock barrel construction too.
The Sabatti double rifle Instruction Manual, that comes with all these rifles, shows calibers they are chambered for, along with normal factory loaded cartridge service pressures for each caliber (page 13):

.500 NE = 2800 BAR (40,610 psi) .375 H & H magnum (belted version) = 4300 BAR (62,366 psi)
.416 Rigby = 3250 BAR (47,137 psi) .450/400 NE = 2800 BAR (40,610 psi)
.470 NE = 2700 BAR (39,160 psi) .458 Winchester = 4300 BAR (62,366 psi)
.450 NE = 3050 BAR (44,236 psi)
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The Standard Directory of Proof Marks, regarding Italian proof, says “Arms with rifled barrels are proofed with a load that creates between 30% and 50% excess pressure” over normal service load, so these actions must absorb between 1,290 BAR (18,710 psi) and 2,150 BAR (31,183 psi) in excess of the normal factory service load for the most severe pressure factory service loaded cartridge these rifles are chambered for, the .375 H & H belted or the .458 Winchester, which both create 4300 BAR (62,366 psi)normal factory cartridge pressure. Thus, for minimum Italian proof of 30% excess pressure over service load, proof equals 5,590 BAR (81,076 psi), while maximum Italian proof, 50% excess pressure over service load, proof equals 7,450 BAR (108,053 psi). Notice that the Italian proof calls for somewhat higher proof, between 30% to 50% higher than service load than does the French proof of 30% higher than service load, so it is reasonable to assume that the proof pressure on these actions, French and Italian, are at least equal, with the Italian Sabatti probably slightly higher. Note: Proof is more applicable to barrel strength than to action strength, so aforementioned BAR pressures, normal factory service loads for specific Sabatti calibers, needs to be observed and not exceeded, but the data contained herein indicates the excellent strength of Sabatti and Verney-Carron double barreled rifle actions, and, certainly, the barrel strength is more than adequate for calibers involved too.

CIP calls for a maximum proof pressure, over standard service load, of 25%, just 5% under the 30% designated by The Standard Directory of Proof Marks for France and Italy, with Italy calling for a designation between the 30% and 50%. I am certain that the upper end figure of 50% is never done, since it is so horribly high pressure, but I am not certain how far above the 30% figure is normally done in Italian Proof Houses. I am quite certain, though, that The Standard Directory of Proof Marks is more accurate than the CIP standards, because I have seen numerous of the aforementioned Sabatti rifles (I own three of them in different calibers), with factory supplied proof certificates that clearly state that proof was done with loads between 30% and 50% above the service loads.

Edited by doubleriflejack (06/02/13 06:55 AM)