I spent a lot of time trying to connect rpm, twist caliber and mv. Looking for a universal relationship. No luck.
Have workbooks and articles/math on these and bullet blow up, pm and I'll send.
CAST BULLET BLOW UP OR BULGE
Do cast bullets "blow up" because they are spinning/rotating due to the rifling? Do cast bullets change shape or "bulge" because of the spinning?
Calculations and explanations can be found in two EXCEL workbooks called "CAST BULLET BLOW UP" and "CAST BARREL HEAT” in EXCEL WORKBOOKS.
Conclusions
Cast bullets can and rarely do blow up at very high RPMs/velocity.
Cast bullets change shape, bulge, at high RPMs/velocity.
Cast bullets are hot as they exit the muzzle, and may/do get hotter going through the air, for some distance-this varies with the load.
Blow up or bulging of cast bullets occurs in a certain RPM area, and is independent of velocity or twist rate and varies slightly with caliber. Plotting the curves of "Centripetal Force = Tensile Strength", and working with the arithmetic shows this to be true. For instance, if a certain alloy bullet will blow up at 400 degrees F, then:
.224 bullets blow up at 126,400 RPM
.308 bullets blow up at 114,320 RPM
.375 bullets blow up at 106,400 RPM
.457 bullets blow up at 98,360 RPM
JLouis wrote on Oct 10
th, 2012 at 10:54pm:
Boats I think this will add some interest to our discussions on twist rates and also help us to get a better understanding on the negative effects of over-spinning. Due the calculation for your current twist rate then up it to the next fastest and one will see the RPM increase is very substantial. All though the conversation revolves around jacketed bullets it directly applies to our lead and tin bullets as well as one will soon realize while reading it.
(You need to Login or Register to view media files and links) J.Louis