I have a steel swinging target that has held up well for 3 years. Last summer I put up a 4 gongs and I am having a hard time with the carriage bolts. The heads of the carriage bolts are shearing off when the target is hit. It happens from 100 yards with anything from 5.56/223 to 450bm. Usually they last 4-5 hits on the smaller calibers and 1-2 on the larger. When the heads are hit (on purpose) they are just fine so I know it is straight sheer forces. Maybe I got 3 bad batches from two different stores. Planning on buying grade 8 carriage bolts if the next batch doesn’t pan out. What is everyone using and how are they holding up?