The SIG S.P.47/8 was developed to compete for succession of Georg Luger’s Parabellum pistol that had been adopted by the Swiss Army in 1900 as the first automatic pistol to be issued in military service. Although the Luger has been simplified, and arguably perfected in its 1929 embodiment by the Waffenfabrik Bern (W+F), it was deemed too expensive for continued production. Its successor was to cut down on the costs while maintaining its stellar accuracy. The legacy of the Luger is clearly seen in one of the modifications of the Charles Petter design that SIG licensed for that purpose in 1937. While Petter’s Modèle 1935A pistol imitated the M1911 in its slide rails riding on tracks in the frame, SIG replicated the Parabellum arrangement that made the upper assembly reciprocate inside the frame tracks. Sig also designed a two-stage trigger that imitated the trigger pull of the Luger, while decreasing its trigger weight, as witness the following test results.
On the Lyman electronic trigger gauge, the trigger of a heavy frame SIG P210-6, serial number P79608, yields a weight of 1.2kg, averaged over 10 pulls. Its immediate heavy frame successor, P79609, fitted with a National Match hammer, releases the sear at an average of 1.23kg. Likewise the heavy frame P210-6, serial number P79103 in 7.65 Para, at 1.24kg. That’s about as good as you can get in a tuned service grade self-loading pistol, and much lighter than Swiss pistol target shooting competitions allow, by requiring a trigger weight above 1500 grams. More typical are the measurements of the heavy frame SIG P210-6, serial number P79136, which yields a weight of 1.82kg, averaged over 10 pulls, the Borchardt C93, serial number 1774, releasing the striker at 2.59kg, and the Krieghoff P08, serial number 3249, weighing in at a hefty 3.48kg.
More Swiss service pistol trigger pull weight measurements follow:
- P06/1929 SN 71644: 3.80kg;
- P06/1929 SN 77493: 2.57kg;
- P06/1929 National Match SN 59951: 2.64kg;
- P06/1929 National Match SN 65721: 2.15kg;
- P210-6 SN P86618: 1.78kg;
- P210-2 SN P79980: 1.67kg;
- P210-1 SN P77209: 1.94kg;
- P210-2 SN P74064: 1.86kg;
- P49 SN A204931: 2.88kg;
- P49 SN A156213: 2.90kg;
- P49 SN A107159: 2.75kg;
- P49 SN A105553: 2.56kg.
All are two stage, with a very crisp stage transition (Druckpunkt). It is obvious which pistols have been resprung. As witness P06/1929 National Match SN 59951 and 65721, W+F was either unwilling or unable to equal, let alone best the measurements of a factory tuned P210, in preparing for the 1949 ISSF competition in Buenos Aires.
The double pull lever is the part responsible for regulating the transition between the two stages of the trigger pull of the P210. After the trigger, part #28, takes up the slack to engage the sear, part #23, by way of the trigger rod, part #26, the first stage of the trigger pull is determined mainly by the weight of the trigger spring, part #31, with additional resistance provided by the sear spring, part #24. As the sear rotates around its pin, part #22, it brings all the way back the hammer, part #14, and contacts the double pull lever, part #21. At that point, the double pull lever connects the sear with the mainspring, part #20, providing considerable additional resistance in the second and final stage of the trigger pull, just before the release of the hammer by the sear.
The double pull lever is individually hand-fitted to the sear and the hammer to regulate the pressure point (Druckpunkt) of the two-stage trigger pull system. If the pressure point is too soft, i.e. if the second stage of the trigger pull has to be strengthened, the top surfaces of two support arms furthest away from the pivot pin of the double pull lever, part #22, must be evenly worked down with an oilstone at the point of their contact with the hammer action housing, part #13. This operation brings the body of the double pull lever closer to the sear. In performing this operation, both sides of the double pull lever must remain perfectly square at the points of their contact with the hammer action housing. The hammer action housing itself should not be modified. If the pressure point is too hard, i.e. if the second stage of the trigger pull has to be weakened, the two projections in the middle of the double pull lever located on either side of the stirrup, part #16, must be evenly worked down with an oilstone at the point of their engagement by the sear, part #23, in the course of the trigger pull. This operation postpones the engagement of the double pull lever by the sear. In performing this operation, both projections on the double pull lever must remain perfectly square at the points of their contact with the sear. The sear itself should not be modified. Never attempt any modification of these parts, unless you are certain of your gunsmithing competence.
In late production, forged and deep hardened milspec sears and double pull levers were gradually replaced by metal injection molded (MIM) parts of slightly modified profiles. This image is taken from Armbruster, p. 193:
Double pull levers used during the SIG P210 production runs. Nos. 1-4 are milled and hardened. From No. 2 the area between the anterior and posterior pressure ridges was reinforced by adding material. No. 5 is the latest version, produced by metal injection molding.
click on the picture for higher resolution
As with all MIM components, these parts are superficially case hardened. They are therefore unsuitable for hand fitting that is liable to cut through the hardening and expose soft core metal in the working surfaces.