Re: 7mm Ultra
I guess I'll give you the long version. It's been quite a ride & hopefully this will save you some of the trials & errors I've dealt with.
When I was deciding on bullets for the 7mm Ultramag (I looked real hard at the STW 1st) I spoke with Walt Berger (Berger Bullets), Jimmie Knox (JLK), & Bob Cauterucio for much needed advice. All are SUPER fine gentlemen, patient, knowledgable & helpful. I can't say enough about each.
Walt ran some RPM figures by me based on estimated velocities & twist rates & readily admitted that his 180 VLDs would be UNlikely to hold together. His bullets are made with very high quality (but very thin) J4 jackets. When my 'smith speced my barrel with Kreiger, they comfirmed it - they'd just had the same idea & the Berger 180s came apart a few yards downrange. I was disappointed because I'd used 70 & 80 grain .224 VLD Bergers almost exclusively in my service rifle for years. Bummer.
I spoke with Jimmie Knox & Bob next. Both make theirs with thicker Sierra jackets. Both hold up fine at 7mm Ultra velocities. If I remember correctly (which is a big MAYBE) Cauterucio 156s were estimated at .690BC & the 176s at .710 or higher. JLK 180s were @ .740 if I recall. That's as close as I can remember, I've slept since then!
These are very long projectiles, the 176s are @ 1.440" with long bearing surfaces to match. Since the Ultra is likely to erode the throat quickly, the length is a plus IMHO to be able to reach the lands prior to re-set.
The thicker jackets are also likely to be a plus for those interested in using them for game - they should hold up well at distance just like a Sierra MK!
I E-mailed back & forth a little with an illustrious member here - Warren Jensen. He has a 162 7mm (.788) that looks intriguing. He also was kind enough to crunch some numbers when asked regarding a theoretical 180 in his state-of-the-art contstruction. He estimates it would be near (gasp) .900 BC!!! It would need a 1:7" twist to stabilize it, but hmmmm........a .900 BC bullet leaving the muzzle at 3,300+ fps....
the possiblities. [img]images/icons/shocked.gif[/img]