(03-23-2025, 11:00 PM)Sockeye66 Wrote: Did get to test a few loads over the chronograph this afternoon, Big Game 28.3gr 87gr VMAX 2450fps, StaBall 6.5 90gr ELDX 2510fps (.7” at 100yds), 28.1gr Shooters World Long Rifle 87gr VMAX 2505fps (.8”), 27.3gr N540 90gr ELDX 2764fps (1.1”), for comparison this rifle (20” CMMG gas gun) shoots the 108gr ELDM factory loads at 2640fps under an inch.Just a quick look at Quickload using the default parameters with 28.3 grains of RS Big Game under an 87 gun V-Max from a 20" 6mm ARC barrel yields 2552 fps at 37866psi. This shows a 91.7% fill ratio.
From this I think we can draw 2 conclusions:
1.As your velocity is 100fps slower than the Quickload prediction, I would say that this powder in this cartridge does NOT model well in Quickload. If we used the actual parameters from your load and rifle we could see if it refines into something closer to reality.
2. According to Quickload, you do not appear to be anywhere near "overpressure". 100% fill ratio would be 30.85 grains at COAL 2.260 an the pressure predicted would be 49651psi. QL's predicted max load would be 31.2 grains yielding 51563psi, 101.1 % fill ratio).
A note of caution: QL shows pressures going rapidly over max with more compressed charges of Big Game in the 6mm ARC. So I would suggest working up slowly and staying away from any compressed charges
The Shooters world Long Rifle powder models much better. QL predicts your load of 28.1 gr under the 87 grain V-Max would yield 2497fps at 38434 psi. Being within 10 fps of your real world results would lead me to have some faith in QL's ability to predict pressures using Long Rifle. However, velocities will be significantly lower than several other choices.