6.5 Grendel Blowing Up Guns?

[Fess]

Thanks for that. GRT way overpredicts Grendel, and this is the first good explanation I've seen on why that might be.

The poor pressure prediction of QL for the Grendel created a big ruckus in the first few years after the cartridge was introduced. IIRC, QL was predicting well over 60K psi for loads that had been pressure tested at below 52Kpsi. I recall that Marty ter Weeme (458 SOCOM and Teppu Jutsu) was credited at the time for coming up with the idea that the case volume was changing quickly because the primer started the bullet moving prior to main powder ignition. A few years ago, I asked if QL has fixed the problem for the Grendel and never got a satisfactory answer. I think that some advanced users just used a larger case volume to get closer to the correct answer.