6.5 Grendel Blowing Up Guns?

[lazyengineer]

The compound throat has confused a lot of would be smart guys.

The interesting thing is that the compound throat and short cartridge in the Grendel actually reduce peak pressures from what QuickLoad and GRT predict. There are to primary reasons for this:

First, the gentle taper in the throat reduces the initial engraving force.

Second, the primer charge slaps the back of the longer bullets before the main powder charge gets into its burn. That results both in a larger case volume and more initial movement than are modeled in the predictors.

Both are difficult to model in either QL or GRT with the core math model they use.

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