The reason for a hard sear like ours which is rated at 55C on the Rockwell scale is an important item in a custom gun. The hard metal will hold its honed edge for the life of the gun regardless of the number of rounds fired. The OEM sear is in the area of 30C on the Rockwell scale and is much too soft for a fire control part, the softer steel will peen into a different shape the more it is shot. This is why the SA trigger improves over time with the OEM sear, it is peened from hammer battering and the nose of the sear becomes a flatter surface. If you look at any of the many high quality parts for the 1911A1 you will find they are all between 45C and 60C, this includes the sear, hammer and disconnector, they are all machined from a solid block of hammer forged steel. Cast and MIM parts do not belong in the fire control components even if they have been hardened because their hardness varies with the depth and type of steel used.
Our company is working with another to produce a hard hammer for the CZ75 series. This will take us to a whole new level of what we can offer to the shooter. When we perform an action job for a customer with one of our hard sears we can tune the action to a much more precise standard and the trigger will not change over time or wear out. When we use an OEM sear we need to leave extra metal to allow the battering from the hammer, thus the sear is going to change its shape in the most critical area and this affects the feel and break weight of the tuned gun. This also requires a mechanical break in period that only live firing will do. Thus we can not guarantee that 2.5lbs trigger will remain at 2.5lbs as the gun is used. However with our hard sear we can guarantee that the trigger will break at the customers specified break weight from day one and on.
Guns require different types of steel for different parts, the frame and slide are relatively soft, this is because they need to absorb recoil from firing, if they were made of hard steel they would be very brittle and crack when fired. The barrel is also a mild steel as it needs to flex and take the shock and pressure of firing a cartridge. But the fire control parts need to stand up to constant battering with out being prone to preening or changes to the shape of the surface areas. The hammer has more metal on and behind its critical contact area with the sear and this is the reason that the soft hammer will hold up to this battering much longer. The angle that the sear nose is cut and honed to has to match the hammer hooks angle, but the amount of sear contact is much less then the hammer so it is the most prone fire control component to battering and preening.
I hope this helps explain the reason for a hard bar stock sear.
Jim
Miossi Gun Works LLC
702 Park Dr
Monticello, IA 52310
