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Posted: 8/1/2015 8:18:05 PM EDT
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I need help with OCW results. I decided recently to get back into 5.56/223 after several years of shooting the Grendel, primarily due to ease of locally sourcing 223 components.
My build specifics: Daniel Defense 18" 5.56NATO Barrel - S2W - Rifle Length barrel YHM clamp on gas block Spikes Upper Toolcraft NIB bcg Seekins/PA rail - nut torqued to 45 ft/lb Optic: Vortex Razor HD 5-20 EBR2B Bench rested on bags I've been testing 75gr Hornady BTHP Match bullets with RL-15. I performed initial OCW testing with a batch of 5 loads. Data is as follows: 75gr BTHP Match @ 2.255" COAL Wolf Small Rifle Magnum Primers Lake City 2014 brass x1 fired, prepped but not weighed RL-15 Loads: 22.1, 22.4, 22.7, 23.0, 23.3 So I guess my question is about the results. I'm a bit confused. I shot the red outlined shots in a "round robin" manner. Once I completed the OCW, I thought the 22.4 and 22.7 looked most promising, so I took 5 shot groups to the upper smaller targets, the green outlined shots above. The groups fell apart to utter crap. Out of 22.4 and 22.7 loads, I shot a 5 shot string of 23 and 23.3 on the diamonds once again, and they grouped much better, despite their poorer performance when shooting the OCW. I guess my question is this: Can anyone make any good recommendations based upon these OCW results? I'm assuming the weak link is me and my AR15 skills, but I'm looking for any suggestions. Thanks. 
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From the looks of your (what I'm guessing is) .308 groups I would say you know how to shoot. Did you let your barrel cool before those last 2 groups? With how they looked in the first 2 groups you shot with them I would try them again with a freshly fouled barrel and keep it cool. Also, were they all loaded at the same time? I have had great groups with trickled loads (that I forgot I trickled) and threw the same thing out of a measure only to be disappointed. |
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Good questions.
I shoot the groups in 5 shot clusters. Reason there's only four in the red groups is due to Chrono testing that was done the day before. Chrono malfunctioned after 4 shots, leaving me with the last group of a full five. I reloaded all rounds in a batch on a single stage. I use a Redding T7. I use a Lee Neck Collet die, followed by a Redding body die to 0.002" bump. I use a Chargemaster to dispense all charges. I allow the scale to settle and discard anything not right on. When I shoot the groups, I shoot all 5 in slow fire. Probably all 5 in under 2 minutes. I then allow the barrel to cool before I shoot the next string, hence the 308 targets that I shoot in between. I cleaned my barrel prior the session, but ran 5 foulers through it before getting into the test. I tried a 200 yard test a few weeks ago, but all groups looked about the same as one another, so I decided to keep it at 100yds where I can really focus on the same point of aim each time. |
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Interesting. You have done everything the best way I know how. The only thing I can think of is to shoot those ones again and see what you get. I know I get fatigued after shooting groups for a while and my focus starts to drift. ETA: And that green 23.3 load is another one I would try again. |
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I had similar problems with OCW results early on. FWIW I can share three things I learned/changed and began to get more consistently readable results.
Because I really didn't understand it, my side-focus parallax adjustment was off. But I believe you have a FFP scope, so that should not be an issue for you. In my case, and among other things, as my angle-to-target changed so did my POA. A lot of people put a lot of faith in the Chargemaster. I do not. While YMMV, in multiple 50-load test runs I've found mine to be no more accurate than (eg) my Hornady PM. And when it is wrong the Chargemaster's variation is wider than the PM's. An additional problem with 223 is that at 22gr the distance between a good node and a scatter node is predicted by OCW to be 0.33gr. When you do not know where the good node is, there is really no room for powder charge variation. I use a much more accurate mag force restoration scale now for load development. If you have a second scale, preferably a beam scale, I'd suggest you double check each and every load when you try again. Finally, while Newberry advocates round robin shooting, I do not share his opinion of the benefits. I prefer to shoot each group as a group, the same way it will be fired "for real". If there is any accuracy deterioration because of excessive heat (avoid by waiting 2 minutes between shots) or barrel build-up, I don't want it to interfere with my interpretation of a group's performance. And by firing groups I'm much more likely to keep my shooting approach/angle/seat-position consistent within each group. |
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I can't tell where your point of aim was on the 308 groups, so its hard to say.
For 223 loads I often find myself testing at close to 0.1 grain increments, and Ill hand weigh each load (not trusting an automatic trickler to do be as precise as that). Round robbin is preferred because it should cause any heat, fatigue, or weather issues to be spread out and taint all groups relatively equally, but to get good data you really need a consistent barrel temp, weather, and a consistent shooter for the entire set. OCW is tough because one 4 or 5 shot group per charge weight is still a really small sample set. If your barrel isnt particularly accurate in the first place it can be mighty frustrating to interpret results. Finding a scatter node to avoid is nearly as good as finding an accuracy node. Look for neighboring groups that shoot to a similar point of aim (regardless of group size) and note any paricularly bad scatter nodes. Consistncy of POI is what were looking for at this stage, not necessarily the smallest individual group. The accuracy node is often a predictable 1-2 steps above the scatter node, so even if you cant pin down the accuracy node you can still guess from the scatter node. Sometimes bullet seating depth needs to be dialed in before accuracy will appear, sometimes a barrel wont like a particualr bullet or powder at all. At the end of the day the likelyhood that your smallest group wont be at the precise OCW node is high so look for consistent POI and decent group size. Unfortunately if a particular session produces confusing results, sometimes you just need to try again of a different day :/. Im getting pretty good at OCW with lots of practice but some days you still can't tell wth is going on from only one group per charge. |
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Download "On Target" scoring software. If you have a scanner, great. If not, photographs just like the ones you posted are fine. You can calibrate a known length, six one inch squares for example, and the program will then provide you with good data.
You use your mouse to designate aim point and each bullet hole. You then get accurate group size, mean radius (average to center), height, width, etc. You can export the data to a spread sheet where you can add velocity information, powder type, seating depth data, and all the other variables you want to study. Then you can sort and study your data with some confidence that you''re getting something closer to the truth than "a quarter can cover my group". You can even graph things like powder charge vs MOA, and Mean Radius, and Group Height to get a real feel for the sweet spot(s). Same thing for seating depth, or whatever you are experimenting with. Shooting is just the first step. Careful measuring followed by a study of your data is where the truth comes out. Make sure to keep the data. For instance, I don't keep details on brass preparation, but I know when I bought my neck turning lathe. My measuring velocity SD against the date I can detect any trends and decide if neck turning is helping or not. Anyhow, your get the idea. On Target is cheap too............only a couple of bucks and I think there is even a free version. |
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I assumed 50 yards. If that's not correct let me know and I can fix it.
It looks to me like you've got a possible node between 23 and 23.3 gr. I would run another round robin test with 23, 23.1, 23.2, and 23.3. This time make sure you give the barrel 2-3 minutes between each shot to cool. I know it's tedious but it pays off. 
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Wow! Thanks "tzzler44" for inputting those for me. I was at 100 yds. I'm going to look into that software, I've seen it before, but never realized the benefit...I get it now.
I'm going to keep trying...I'm coming up on some time off, so I should be able to generate some good data soon. I really appreciate everyone's input. Thanks! |
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