Originally Posted by backwoods83
Well since I have no idea what I'm talking about and over stabilization "doesn't cause worse spin drift" then load a 168grn berger vld in a 10 twist 300 wby at about 3400fps and see what happens with that! Because I'm just another jacka$$ that has no idea what he's talking about.
A guy that should know once told me that a typical VLD needs a minimum of 179K rpm to stay stable in flight. Now that was many years ago when we were shooting for a .6 B/C. For the longest time I kept track of Walt's statement, and found it to be fairly accurate, but not perfect. Maybe for a .55 B/C, but since then I've come to the conclusion that the higher the B/C number the higher the rpm at impact is needed. But what Walt didn't tell me was that too many revolutions per minute is almost as bad as not enough! Later on a couple guys that hang with the Fairland bunch made an inquiry as to who could help them mod some bullet making dies. I got the call. The needed several punches made in some really wierd diameters (step punches at that). I didn't know that old man from Adam, but he seemed pretty nice and also seemed to know what he was talking about. I made about a half dozen punches for him, and I get a call to drop buy for a few minutes. He gives me about fifteen hundred benchrest quality 66 grain, 67 grain, and 68 grain bullets in 6mm. Best bullets I've ever used! We had a long conversation about bullet designs, and he went way over my head. He went into the idea of bullet stability and twist rates as well as the rpm factors. Then he explained why groups open up when they shot so well before. We all tend to drive them too hard! Now I got more bullets than I know what to do with! He had a tool built that checked bullet shapes with several one tenth dial indicators, and another that actually checked the C/G of his bullets. I watched him check about a dozen bullets, and everyone of them ran about .000050"!! Then he took some hunting bullets from a well respected bullet maker and set the gauge up for them. They were all over the place, with some being out as much as .0005". That's when he sat down and explained what we just checked and what happens to the bullet in flight. The bullets, when spun too fast tend to open grop sizes dramaticly due to shape errors and C/G errors. One ten thousandth of an inch equales about .093" displacement at 100 yards. Later he has me build him a dozen different .224 punches, and wants to give me enough bullets to shoot three years. I told him I just couldn't take them for no more than what I did for him. They were on my door step the next day when I came home from work! I did get to watch him form 53 grain bullets and some that were around 63 grains. I promised to not tell anyone about his process, but let me say "I still can't believe what I saw."
What I learned was that with a given twist rate and a certain rpm window; good bullets will group very tight. Yet if I stepped out on the window those groups will grow in size. How good was that old man's bullets? They've set more than one record at one time or another.