What in Tarnation is happening to my bullet?

Ian

Notorious member
PREFACE....I drifted off and didn't get this posted last night either.

Oh, ok NOW we get the velocity. You were shooting popgun loads from your M1 Rifle last I heard, I shoulda clicked the thread you linked instead of assuming. I've mentioned several times how my results with that RD copy stunk, it wants to swap ends and never shot straight at any speed for me, reference Fiver's post above.

As to BC, I'd trust the LabRadar a helluva lot more than the bullet design software Al uses. After all, the BC calculations based on the Doppler capability of the machine is one of its strongest points and is giving you ACTUAL results. There's nothing on that blunt nose to slump, anyway, so you can be pretty much assured it isn't changing form very much at .30-30 pressures.

I've used two chronographs, pre-calibrated to each other (or rather shot together at the muzzle and 15 feet and the offset figured in), at different distances to figure approximate BC and have been very surprised by some of what I learned. If you boot a 10 bhn spire point cast bullet in the pants with 50K PSI the BC goes to pot real quick. It isn't nose slumping, it's filling from behind. The blunting and fattening of the nose isn't the cause of reduced BC as much as the bullet actually shortening up.
 

Bret4207

At the casting bench in the sky. RIP Bret.
Makes sense Ian. It also makes sense that there's a typo in the cataloged BC.