Adjusting QuickLoad for VihtaVuori powders

[cwsanfor]

As described in another post, I had some rounds turn out much slower than QuickLoad predicted, and am curious if you have had the same issue, particularly with VihtaVuori powders.

I was loading 125 gr HAP over VV N330, and got deviations of up to 170 fps slower than predicted chronographing the rounds on a Shooting Chrony. Got a bullet stuck in a barrel as a result. To match up the predicted versus actual velocities I adjusted the Max Case Capacity from 13.3 to 13.8 (per my physical measurement), and had to adjust the Burning Rate Factor (Ba) from 3.1 to 2.6, putting it down in the N310 range. That seems like a lot, but my predictions with N330, N340, 3N37 now jive pretty well at all loadings. I have not had this problem with Power Pistol or TiteGroup, so the issue so far seem specific to VV powder. Anyone else seen this?

[G-ManBart]

Nope, it's been eerily accurate for me using N320, N350, 3N38, 3N37 and N105 data. I'm using VV powders in 9x19, .38SC, and .40S&W, so I don't think it's cartridge specific. I have noted some pretty large increases/decreases due to OAL changes, but that's the only thing that has really stuck out to me. R,

[cwsanfor]

The VihtaVuori N330 consistency was not the problem. I went back and checked QuickLoad against a bunch of known loads, and the unadjusted burn rate was dead on in every instance.

I was getting bad chrono readings because of light hitting the sensors on my Chrony. I built a "coffin" with LED lights, and am shielding the sensors with index cards when needed. Sort of a lot of trouble, but the range where I can chrono runs east-west, and has trees all around, so consistent light during the day is a problem. Not as big a potential problem as when you adjust your burn rate in QuickLoad and inadvertently load a bunch of 45,000+ psi rounds (I thought they felt a bit snappy). I'll pull the remaining rounds or freeze them and shoot them this winter, since I do not have a reason to shoot 9mm Major, particularly unintentionally.