Thread: Anyone played with 223AI?

Originally Posted by sneeze

Some things to think about here, firstly stating velocity/pressure without referencing barrel length and powder burn rate is not particularly useful. Pressure in internal ballistics is not linear, you can reach higher velocities with lower peak pressure by flattening the pressure curve or "increasing area under curve", usually by using a slower powder or/and reducing start pressure. Some of the new double based powders give benefits here. Or by simply using a longer barrel.
Looking at your conclusion of 60,000 CUP to gain 3000fps in a 6.5x55ai equates to around 73000psi. I would expect to see substantial case head expansion at those levels making the case unusable in a couple of cycles. If the users running their 6.5s at 3000 are getting good case life then I would suspect the pressure would be considerably lower than 60000 cup.

Greetings @sneeze,
Thanks for your reply. I don't dispute any of the points you make on the newer powders, barrel length etc. My point was that most of the gains in velocity could be made with the parent case. I also said approaching 60,000 CUP so likely closer to 70,000 PSI. John Barsness also suggested in his articles that 70,000 PSI was around the level of pressure that hot shot handloaders worked up to by looking for pressure signs. I have loaded some pretty hot loads in the 6.5x55 over the years, initially through ignorance and recently almost caught out by the significant increase in speed of AR2209 about 20 years ago. There have also been some learnings about significant changes in velocity and likely pressure between different projectile of the same weight including projectiles of the same manufacture and cat no. Now I prefer to keep a decent safety margin rather than trying for that last erosive foot per second.
Regards Grandpamac.