I was braced for disappointment with the IMR 3031 with the 55 grain FMJ-BT bullets, and the lower end of the workup met my expectations. I'd done some adjustment of the tightness of my riser rail and sight before I hit the range, and found my POI was a little low and left. Before the last string int this workup I did some adjustment, and ended up over-adjusting. I pulled the second shot in a string of 5, and ended up ricocheting the bullet off the bottom of the steel rail above and behind the target. This made a mess of the target, and put tears all over it. I finished out the rest of the string, and moved on to the other workups. I got home and started looking at the chronograph data and found that the last set of 3031 charges had a nice and tight velocity spread. Average velocity was 3089.05 fps with an ES of only 53.33 and a SD of 20.17. I pulled the target out of the stack, and holy cow! The other 4 shots were in a 1/2" group!

This particular charge was a compressed load at 24.8 grains and an OAL of 2.230", and the grouping difference between it and that lower charges was quite pronounced. This 3031 load, in fact, outperformed all others that day. Data for the load was from the Lee manual.
I also got decent results with Benchmark at 24.9 grains and an OAL of 2.235. I got this data from Hodgdon, and adjusted this from 2.220" to 2.235, as their data only lists soft point bullets in 55 grains. I ended up getting a grouping of 1" for that load, though there was considerable lateral deviation, so part of that may have been me.
On to the 70 grain Speer Semi-Spitzer bullets that I'm using to develop a hunting load, I tried 3 different powders: IMR 3031, Hodgdon Benchmark, and Ramshot TAC.
I tested the 3031 loads first. These gave very good velocity spreads, with the best spread at 9.77 fps and a standard deviation of only 4.35. Unfortunately, grouping wasn't nearly as good, with the best being around 1 1/2". I realize this might by improved by adjusting OAL (I had these at 2.150"), but these loads are being developed for hunting, and I don't think 3031 can give me the velocities I'm looking for. The hottest load out of the group at 21.1 grains (max listed by IMR is 21.2) only came out to a velocity of 2503 fps.
Next up was Benchmark. I actually got some pretty decent grouping with the low end load at about 3/4", but this was somewhere under 2300 fps. The higher the velocities went, the more the groups spread out, until the last string, where it tightened back down some at 22.6 grains at a velocity of 2650 fps. The top end of the data from Hodgdon uses 22.8 grains. At some point, I may see if I can find 5.56 NATO-spec data for Benchmark and see if it tightens down some more at higher velocities. OAL was also set at 2.150", so OAL adjustment may make a difference here as well. Either way, the loads need faster velocities for hunting. Velocity spreads were also very good with Benchmark, and were similar to what I saw with the 3031.
Finally, I tested my Ramshot TAC loads. This was actually the second time around with TAC. 3 weeks ago, I went to try out all these loads and arrived at the range only to realize I'd left them all at home except for the TAC. I'd done a workup from the data published by Ramshot. It seems to me that Ramshot may be subscribing to the Hornady method of overstating load velocities, because the .223 spec loads had such a disparity in velocities that I don't think the barrel length difference was enough to explain it away.
So... I did some googling and found a fellow who corresponded with Ramshot about 68 grain load data for the 5.56 NATO spec. Working from the lower end of these (picking up just above where I'd left off with the .223 spec loads), I worked up a new set of TAC loads using LC NATO brass instead of the PPU and Federal .223 I've been using for everything else. Ramshot's 5.56 data starts at 23.5 grains and goes up to 26.2 grains. Unfortunately, I'd run myself out of bullets, and only had enough for 20 rounds. I started at 24.0 grains and incremented by 0.3 grains up to 24.9 grains, with OAL at 2.155". I got good results from the 24.9 grain string, with an average of 2814.45 fps, a spread of 20.15 fps and a standard deviation of 9.53. Grouping was about 1", mostly lateral deviation so the load will probably peform better than that. Once I get a hold of more of these bullets, I'm going to do another workup, probably starting at 24.8 and incrementing up by 0.2 grains up to 25.6 and see how those do.

I stopped by McBride's today in the hope that they carried the 70 grain Speer bullets, but apparently they do not. What I did find was the fable IMR 8208 XBR powder that I've heard all kinds of good things about, so I picked up a pound, along with some Sierra 69 grain HPBT bullets. I'll have to do some workups with this stuff and see what they can do.