GRT and 7/6.5 PRCW

[goneshooting]

I am trying to model my 7/6.5 PRCW in GRT and immediately ran into high pressure issues.
I used the 6.5 PRC cartridge to start with and then changed the neck to .284, barrel to 32 inches, cartridge OAL, and bullet info to Berger .284 180 gr hybrid target. I used my match load of 54 grs of RL 16 and GRT immediately displayed the High Pressure warning . The velocity was about 80 fps high but I corrected that in OBT to my verified velocity of 2,885. Still got high pressure in GRT, about 74,000.
The window around 54 grs of RL 16 is widely used by shooters and shows no signs of over pressure in my gun.
Can someone explain what's going on and how to deal with the high pressure warnings in GRT.

 

[chromatica]

I did load testing with RL16 in 6ARC and noticed that my measured velocities were 200 fps slower than predicted by GRT. I suspect that the thermodynamic properties Gordon specified for RL16 are incorrect. In particular, I believe that the heat content per unit weight is set way too high. That would explain the results you are observing.

 

[goneshooting]

I wondered about the powder being off but RL 16 shows as a powder with lots of input from shooters. Oh well...