10-11-2020, 04:32 PM
Growler,
Great points. I used properties for AISI 9310 VAR (material used for the Monster bolts) that I found on the web. The yield and ultimate strengths can vary due to heat treat differences, but the values I used are representative I think. Also keep in mind that the properties listed by a supplier are guaranteed minimum capabilities, and the actual nominal strengths will generally be higher that what is listed on the spec.
For sure I agree that the barrel extension could be the culprit for poor bolt lug contact along with other misalignment issues such as a non-true receiver face etc.
As far as fatigue failure goes, a good estimate of stress-based fatigue endurance limit is 1/2 of the ultimate strength, so the SF of 3 or so should provide high fatigue resistance. The types of bolt failures that are generally described as occurring in 10s or 100s of cycles are actually low cycle or very-low cycle fatigue failures from repeated high strain cycles. I think this could only occur for cases that I mentioned in the original post and should not be a concern for a nominal build.
- PA
Great points. I used properties for AISI 9310 VAR (material used for the Monster bolts) that I found on the web. The yield and ultimate strengths can vary due to heat treat differences, but the values I used are representative I think. Also keep in mind that the properties listed by a supplier are guaranteed minimum capabilities, and the actual nominal strengths will generally be higher that what is listed on the spec.
For sure I agree that the barrel extension could be the culprit for poor bolt lug contact along with other misalignment issues such as a non-true receiver face etc.
As far as fatigue failure goes, a good estimate of stress-based fatigue endurance limit is 1/2 of the ultimate strength, so the SF of 3 or so should provide high fatigue resistance. The types of bolt failures that are generally described as occurring in 10s or 100s of cycles are actually low cycle or very-low cycle fatigue failures from repeated high strain cycles. I think this could only occur for cases that I mentioned in the original post and should not be a concern for a nominal build.
- PA