RockyMtnMT
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We have been able to gather some great data recently. We have a customer that contacted me a while ago with questions about bc of our 88g in his 6 Creed Hammer Hunter. He was needing an extra 3 moa more adjustment at 725y than expected. We spoke for quite a while and determined that he was doing everything correctly. He is shooting sub 2" at 725y so not all bad. We see a rifle do this every now and then. It is obvious that there is something happening to the bullet while in the barrel In our conversation I found out that he also had a 243 win that had the same twist barrel. The only diff in the two barrels is that the 6 Creed is intentionally 1 thou smaller bore dia. I asked him if he would load up the 243 win and see what it would do. He is a nut like me so he was very willing to do the testing. He called me back a couple of days later and the 243 needed 3 less moa and ran right with our bc. Good news, but still frustrated.
A few days went by and I woke up in the middle of the night with the theory that the tighter bore is engaging the tangent ogive farther in front of the shoulder than the standard bore causing the degraded bc. So I contacted him to see if he would be willing to do some more testing. He was in, so we designed a secant ogive bullet for him to test in both rifles. With the secant ogive the engagement of the lands in front of the shoulder will be significantly less diff between the two rifles. He loaded up both rifles withing 10 fsp of each other. At 725y the 243 shot 1" higher than the 6 Creed. Basically identical.
This is a small sample but I am convinced that the issue of poor bc now and then is caused by tight bore or lead angle causing disruption farther out in front of the shoulder of the bullet with our tangent ogive. With this knowledge I think we will be working on secant ogives on future bullets or other variation of ogive design to eliminate the premature land engagement on the nose. We will not be changing or discontinuing any of the current bullets. So don't worry about that. I am quite excited to have learned what causes this!
A few days went by and I woke up in the middle of the night with the theory that the tighter bore is engaging the tangent ogive farther in front of the shoulder than the standard bore causing the degraded bc. So I contacted him to see if he would be willing to do some more testing. He was in, so we designed a secant ogive bullet for him to test in both rifles. With the secant ogive the engagement of the lands in front of the shoulder will be significantly less diff between the two rifles. He loaded up both rifles withing 10 fsp of each other. At 725y the 243 shot 1" higher than the 6 Creed. Basically identical.
This is a small sample but I am convinced that the issue of poor bc now and then is caused by tight bore or lead angle causing disruption farther out in front of the shoulder of the bullet with our tangent ogive. With this knowledge I think we will be working on secant ogives on future bullets or other variation of ogive design to eliminate the premature land engagement on the nose. We will not be changing or discontinuing any of the current bullets. So don't worry about that. I am quite excited to have learned what causes this!
