Hello Don,

I don’t know where the dividing line between standard velocity and high velocity falls. I don’t think that defining the dividing line is important. Some consider the ammunition up to 1150 to be standard velocity.

My opinion is that there are a number of target rounds both high end and practice quality that are available at 1080 feet per second. In my opinion, the shooter should not be trying to find the highest velocity he can get away with without harming the gun. He should be trying to find the ammunition that is accurate reliable and the one that will be the easiest on the gun (closest to 1080 feet per second).

The discussion about cracked frames seems to center on the ammunition velocity and the slide. These are certainly two important factors in the problem and are perhaps the only ones that the user has over the problem. Keeping a fresh spring in the slide and using ammunition in the 1080 feet per second is the best you can do for the factory you have control over. Jim Barta, whose opinions on this issue I greatly respect, recommends 1080 and a 6.0 pound variable rate spring that is to be changed every 10,000 to 15,000 rounds or whenever the force to keep the slide open to just short of the stop lug is less than 5.0 pounds. The standard spring is 5.50” constant rate spring which is also acceptable if you observe the minimum spring force.

What the frame strength is because of where it falls in the manufacturing tolerance for heat treat is a factor you have no control over. The stress concentration factors due the geometry of the frame in the area around the historical location of the frame cracks in the High Standard frames are all the result of machined surfaces - sharp corners and locally thin sections. The tolerances of the section thickness is a significant percentage of the total section and there is no specification for radius corner mills and broaches which might have helped.

Another factor we do not have control over is the number of rounds already fired and the condition of the spring when they were fired. This frame crack is a fatigue failure and is the result of cumulative stressing above the endurance limit.

There is one instance reported on this forum where the owner bought the gun new, fired only standard velocity ammunition and the springs changed yet the frame cracked.

A stack of the dimensional tolerances show that the thin wall behind the slide lock can vary from .058" down to .039" which at the minimum material condition of the tolerance would mean a stress that could be up to 1.5 times what it would be at the maximum material condition. This would be further magnified by the stress concentrations due to the local geometry. Sharp radii, great change in section, and rough machined surfaces all contribute to greater stress.

John Stimson