Trip report 28 January 2012, developing 10mm rounds
I loaded four ladders for eight powders (VihtaVuori N105, Alliant Blue Dot, VihtaVuori N340, VihtaVuori 3N38, Hodgon Longshot , VihtaVuori 3N37, Accurate Arms #9, and Alliant Power Pistol), with the hottest loads limited to about 36,000 psi or about 5% compression, whichever came first, and worked up to that with three loadings reduced by 0.2 gr each step, except in the case of PP and LS, which were reduced 0.3 gr per step. I used new Starline brass with 0.987" length, 24.6 gr H2O MCC, COAL 1.26"; bullets were 180.3 gr Precision Delta FMJFN; primers were Federal LPP; rounds assembled on a Hornady LNL AP (but hand-weighed to 0.1 gr, not dropped) with Lee dies. The gun was a G20sf with 4.5# connector, Bar-Sto 4.61" barrel, and 24# ISMI recoil spring, benched. Quickload (QL) and ambient temp 45F, 12' muzzle to chrono, 14' chrono to target.
The results in the original format (four groups of increasing powder weight for all eight powders) is at https://docs.google.com/a/sanfordcon...hl=en_US#gid=1. I rearranged the data into what I think is a better format at https://docs.google.com/a/sanfordcon...l=en_US#gid=10. The latter format shows all four rungs of a ladder on one sheet, and (1) simulates the way I'd ordinarily shoot a ladder, one powder at a time, so I can feel the effects of increasing weight; (2) facilitates adding graphs for Pressure versus Velocity and Actual versus Predicted Velocity; and (3) will be the format I use going forward.
The grouping data is probably marginally useful, because shooting groups at the same time as chronoing is distracting, and I sometimes had to reposition the point of aim to avoid shooting the chrono, etc. I'll shoot groups later for selected rounds without a chrono. However, although a low standard deviation (SD) is not always associated with increased precision at the target, the SD's here give me some clues as to what loads to pursue.
VihtaVuori 3N37 seems to be the SD winner, and tracks QuickLoad (QL) very closely, although the N340 was also good. The Power Pistol (PP) load I was fretting about, 9.9 gr, was just fine, and was the third highest in velocity of this bunch, 1,303 fps at 36,252 psi. Going above 9.9 gr does not noticeably increase velocity in PP with this round, according to QL. LongShot ran fastest, 1,324 fps at a comfy 35,829 psi. There's only about 20 fps more available before exceeding 37,500 psi. BlueDot (BD) was second fastest (1,319 fps at a mere 28,514 psi). If you are comfortable with 17% compression and about 38,000 psi, which I am not, I believe BD would run about 1,370 fps with this round's parameters, although I would not recommend this, particularly at colder temperatures, because of BD's pretty clear inverse temperature sensitivity and somewhat odd pressure/velocity characteristics. Speaking of which, I got this email from the Technical Service Manager at Alliant this week: "Blue Dot does up a bit at cold temps. I do not know how this could be put into the QuickLoad system. I will pass your comments on to one of our engineers for their comments.". I hope to get better factors including Ba for BD, but I know of no way for QuickLoad to account for inverse temperature sensitivity, so I will not likely play much with that.
I'm likely to stick with VV powders for less flash, less soot, and better metering, and PP when I want to save some money. That's kind of my general strategy anyway. I think 1,270 fps is all I can comfortably get from 3N37 (at 37, 628 psi), but the truth is I don't plan to load everyday 10mm much faster than 1150-1200 fps.
So it was a good day at the range. My BIL brought down his AR-15, a jacked up piece with too many mods to mention. It shot sub-MOA like a breeze at 250 yards. Cap'n Tom's was not open, so we ate at the Blue Mist BBQ, which was okay, but it is certainly not Lexington #1, the Finest BBQ in The Universe. South Carolinians, please hold your comments. Charlie was so enamored of my BIL's H&K USP .45 that he hardly shot his own G27.
Glock Armorer 2011
Glock Gen3 G20sf/34/22/19/26
Hornady LNL AP, Lee Classic Cast SS