Any idea where those numbers came from for the limit?
The math is mine, and yes it's simpleton.
~30yrs ago, overbore cartridges were very popular for a while.
22-243 wildcats, with 90gr VLDs, presented a razor thin balance between stability (at req'd 7tw), and bullet blow-ups.
It was so common, and so consistent, that it could easily be predicted within 100fps MV.
The 90 SMKs consistently failed 10krpm higher than Berger VLDs, but that's only 100fps of margin, so my defining of failure seemed useful as conservative where Berger VLDs failed.
So if easy to predict 22cal VLD failures, I figured it might be as easy with other cals.
I reviewed and watched all failures reported at every shooting forum of the time(I looked at it for ~5yrs). With overbores being so popular, it was pretty easy to find failures in every cal through 30. It turned out that the math held well with a cal adjustment.
Also,
this is with appropriate twist rates for heavy for cal jacketed bullets. A condition where a risky balance would show up for overbores capable of causing failures. It was NEVER a problem for normal capacity cartridges and proper twist rates per cal.
It's not actually about RPMs alone. It's about the friction/heat energy applied to provide the RPMs for high bearing area bullets.
I assume that even thicker jacket Target VLDs would fail where SMKs would also fail (~10 KRPMs higher than my formula predicts).
Notice little to no chatter about failures from any bullets today? There will be soon, as overbores are coming back, along with even longer bullets. My math will likely hold up just the same again,, but I'll be watching.
