It was a nice day at the range today. A bit windy as usual there, but otherwise it was nice shooting weather.
As mentioned a couple posts ago, I'd worked up loads with a few different powders and a couple of different bullets. I got the chance to take them out to the range today to see how they ran. I got a bunch of 5-target sheets from Midway with my last order. These utilize five 3 15/16" bullseyes on cheap newsprint-quality paper. They're very inexpensive, so are great for testing load workups.
I had two powders I did workups with for the Winchester 55 grain FMJ-BT bullet: IMR 3031 and Hodgdon Benchmark. I was surprised to actually find useful and accurate loads in both powders.
I'd not had a lot of faith in IMR 3031, as the key benefit of the powder when it was sold to me is that it burns clean. That is a nice characteristic, but certainly not the primary factor for me when choosing a powder. Using the Lee manual as a guide, I made a workup from 23.0 to 24.8 grains, in increments of 0.3 grains. The top end of this is a compressed load. I don't understand the dynamics of compressed loads very well, other than the fact that some powders don't work well with compression, while others do. OAL for this set was 2.230".
I had the chronograph out and had my spotting scope handy to see the results of my work. I made my way through the 3031 group, not seeing anything particularly notable as far as grouping size was concerned. I did see that my shots were grouping a little low and left, so made some adjustments just before the last group of the batch. I ended up over-adjusting and pulled the second shot, which hit a little too high and ricocheted off the bottom edge of the top post above my target. This caused all sorts of nasty tearing on the target, and I figured it didn't matter much, considering the performance of the powder up to this point. I finished up the string and moved on.
I brought all my targets home for review, going through the data for each one. I saw that the last string of the IMR 3031 showed a much tighter spread and Standard Deviation than the rest. Average velocity was 3089.05 with a spread of only 53.33 and a SD of 20.17. I went and looked at the target, and in the mess of the ricochet, found the rest of the shots in a 1/2" grouping!
I think I may do a little tuning work with this powder and explore the top end to see what I find. This was definitely a surprise!
The Benchmark workup performed well. I did a workup from 24.0 to 25.5 grains, in increments of 0.3 grains. Data was based on the Hodgdon load, with OAL adjusted to 2.235" from the 2.220 that was listed for a soft point. It looks like the accuracy sweet spot is somewhere around 24.9 grains at an average velocity of 2982.89. Consistency here was good as well, with a spread of only 37.53 and a standard deviation of only 14.59. Grouping was around 1".
Moving on to the hunting load workups, I created workups for both powders mentioned above, as well as with Ramshot TAC, which I've heard good things about in conjunction with the Speer 70 grain Semi-Spitzer.
I started out with the IMR 3031 loads first. This workup was based on the loads from the Hodgon website, and ranged from 19.0 to 21.1 grains with OAL set to 2.150". Grouping was OK, but nothing below 1.5". The best group also had very tight velocities, with an average of 2430.11 fps, a spread of only 9.77 fps and a standard deviation of only 4.35. Looking at the data overall, the powder stayed very consistent throughout the workup. I may work on this powder a bit and see if an adjustment to OAL makes any difference in grouping. They definitely need to be stoked hotter to hit acceptable velocities for hunting - the highest velocity I got out of this workup was 2503 fps.
Next was the Hodgdon Benchmark. This workup went from 20.8 to 22.6 grains, with an OAL of 2.150". I actually got a nice 3/4" group with my starting string, but grouping seemed to progressively open up the higher the velocities got until the last group, where they tightened down a little. The high end of this workup only got up to around 2650 fps. Velocity consistency was actually very similar to the 3031, with extreme spreads generally staying around 25, more or less.
Finally, I tried out the revamped Ramshot TAC loads. While Ramshot only publishes .223 loads (which seem overstated in velocity), they have data for 5.56 NATO spec as well. I found someone who'd put this information up on their site after corresponding with Ramshot, so I gave it a try. The listed range (for 68 grains) starts at 23.5 grains up to a max load of 26.2 grains. I picked up just above where I left off, and started at 24.0 grains, with 0.3 grain increments. I'd run low on these bullets, so only had enough for 20 rounds. Since this were NATO-spec charges, I used Lake City brass instead of the the Prvi Partizan or Federal .223 brass I have been using for most of my loads. Grouping tightened up at the top end of my workup, and I got about 1" at 24.9 grains. OAL was set to 2.155" The 24.9 grain group gave good results for velocity, with an average of 2814.45 fps with a spread of 20.15 fps with a standard deviation of 9.53. Once I get some more bullets ordered, I'm going to do another workup with this powder and increment by 0.2 grains and get a little higher that I did with this set.
It looks like TAC is in good shape for becoming my hunting load powder, so I'll keep you posted here.
I also promised a re-evaluation of the S&B 5.56 ammo that I picked up at Cabela's. I had some extra time at the end of my workup tests, so I figured I'd put 10 more rounds through the rifle to see how it measured up this time around. Results were significantly better, with about 1 1/2" grouping, excluding 1 flyer.
That's all I've got for you now. I'll keep you posted on new development efforts.
Gratuitous Gun Pr0n #162...
2 hours ago