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Posted: 5/16/2022 1:22:15 PM EDT
 Hopefully this will spark some discussion. Which one would you go with and why? This is for an AR308. From left to right: 2.832, 2.813, 2.803, 2.791, 2.781. These are OAL, I have the BTO in my notes on each one. |
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Posted: 5/16/2022 1:36:30 PM EDT
[#1]
2.81
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Posted: 5/16/2022 1:45:19 PM EDT
[#2]
Just based on that probably 2.81".
Are the results repeatable? Do your groups tend the same way when you shoot 5 or 10 rd groups? |
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Posted: 5/16/2022 2:08:43 PM EDT
[#3]
Coincidentally amongst 3 different AR10’s and 2 bolt guns, with all different .308 chambers of some sort, from factory Remington, custom throated obermeyer, Noveske, etc, I settled on 2.815 with 168 and175 Sierra and lapua 175 Scenar LS, so your 2.813 is looking good to me.
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Posted: 5/16/2022 2:23:14 PM EDT
[#4]
Either 2 or 5.
I would shoot 3 more 10 round groups with each of them and really see what is going on. |
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Posted: 5/16/2022 2:30:38 PM EDT
[#5]
Quote HistoryQuoted: Just based on that probably 2.81". Are the results repeatable? Do your groups tend the same way when you shoot 5 or 10 rd groups? Exactly where I would go, a single set of three shot groups that are kind of similar have little significant value. I repeat test with 5 shot groups, sometimes making the increments smaller based on an area that shows promise. They compare the second set to the first set, would the be the same if overlaid one sheet on top of another or would you have a bigger group and bigger statistical significance. |
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Posted: 5/16/2022 3:10:06 PM EDT
[#6]
Quote HistoryQuoted: Either 2 or 5. I would shoot 3 more 10 round groups with each of them and really see what is going on. This is my vote as well. |
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Posted: 5/16/2022 3:12:28 PM EDT
[#7]
I load semi-auto OAL" for reliable feeding and function. Simply establishing a 2.800" OAL" and adjusting powder charges for my best groups.
Not all magazines will allow anything longer. I think my M1-A's will accept 2.830", but I never load that long. I want my ammo useable in any firearm in an emergency. I competed for over 10 years with M1-A's that would flirt with 1.5 moa, usually closer to 2.0 moa. I made master in 1989 and my personal best score was a 489/500 with 22x's. I normally fired high 190's at the 600 yard line, my best position. Offhand was always challenging. All groups were fired with iron sights and my moa's reflect that. What the rifle would do scoped from a bench I have no idea. All NRA/CMP targets have 1 moa x-rings and 2 moa 10-rings. Any rifle that can shoot 1.5 moa at 600 yards will clean a target provided the shooter does his part. 12" circle at 600 is pretty tight. I load for safety first, reliability second and accuracy last. Because of the nature of tournaments, all groups fired are 10 to 20 rounds plus 2 sighters in NRA events. No sighters for CMP, you are supposed to know your rifle zeros when shooting CMP. |
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Posted: 5/16/2022 4:10:56 PM EDT
[#8]
These are repeatable, similar results with this charge weight. I have another lower charge weight I'm working with as well.
For those of you that picked 2.81, are you picking it bc it's the tightest group? |
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Posted: 5/16/2022 4:27:15 PM EDT
[#9]
Quote HistoryQuoted: Exactly where I would go, a single set of three shot groups that are kind of similar have little significant value. I repeat test with 5 shot groups, sometimes making the increments smaller based on an area that shows promise. They compare the second set to the first set, would the be the same if overlaid one sheet on top of another or would you have a bigger group and bigger statistical significance. |
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Posted: 5/16/2022 4:42:01 PM EDT
[#10]
I would shoot some 5 and 10 round groups, and see if the results are repeatable. An occasional small group doesn't prove much, it is when the groups are repeatable that it becomes important.
My experience is that if the wind variable is removed, groups will string vertically if pressures are low, then when reaching optimum pressure/accuracy groups will become circular. As you go over optimum pressure, the circular groups get bigger. You have a couple of nice groups, so I would again try to see if the results are repeatable before I accepted a 3 round group as indicative of true, repeatable performance. I agree with previous postings that suggested firing 5 or 10 round groups to see if the results can be repeated. |
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Posted: 5/16/2022 5:04:07 PM EDT
[#11]
Quote HistoryQuoted: For those of you that picked 2.81, are you picking it bc it's the tightest group? |
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Posted: 5/16/2022 5:07:18 PM EDT
[#12]
Quote HistoryQuoted: Obviously more rounds would add to the statistical significance and that in itself is going to increase group size. I would tend to disagree that this particular test doesn't have value. The goal is not the smallest group size for this test. Quote HistoryQuoted: Quoted: Exactly where I would go, a single set of three shot groups that are kind of similar have little significant value. I repeat test with 5 shot groups, sometimes making the increments smaller based on an area that shows promise. They compare the second set to the first set, would the be the same if overlaid one sheet on top of another or would you have a bigger group and bigger statistical significance. I understand that but three shots is almost telling you harmonics by group height is still just three shots. As a start, I have no problem with it but I am not going on a production run based on just that. You likely aren’t either. Based on the above though I’d look around the second length. It is “even/ round” as opposed to the others that are slanted perhaps due to barrel harmonic movement. |
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Posted: 5/16/2022 5:44:55 PM EDT
[#13]
Quote HistoryQuoted: A little longer and shorter still groups snugly, particularly on the vertical spread. Should give more margin of error. I was also looking at the vertical as well, they seem to be pretty similar across .030". |
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Posted: 5/16/2022 5:55:08 PM EDT
[#14]
Quote HistoryQuoted: This aligns with my thinking as well. But I was looking at 2.832 as a place of interest to give me the best durability, particularly as the rifling erodes overtime. I was also looking at the vertical as well, they seem to be pretty similar across .030". Quote HistoryQuoted: Quoted: A little longer and shorter still groups snugly, particularly on the vertical spread. Should give more margin of error. I was also looking at the vertical as well, they seem to be pretty similar across .030". Not a bad way to figure it. I do the same on a powder node,...if I have a wider flat node across severalcharges I will skew toward an edge for a temperature difference of when I am working up loads and a hunting load I will use at a 40-50 degree lower temperature. As long as it is a safe load in the warmer temps I got that much more room to stay with the node as velocity drops as temps drop. |
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Posted: 5/16/2022 6:32:54 PM EDT
[#15]
2.813...seems to be the sweet spot, plus smaller group size. but...3 shot vs. 5 shot it may open up on 5
No given everthing else is equal just depth is the variable.. deeper depth more pressure. -Garland |
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Posted: 5/16/2022 6:36:00 PM EDT
[#16]
Quoted: From left to right: 2.832, 2.813, 2.803, 2.791, 2.781. These are OAL, I have the BTO in my notes on each one. Also, I would like to see groups for "OALs" of 2.807, 2.810, 2.813, 2.816, & 2.819. |
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Posted: 5/16/2022 6:58:46 PM EDT
[#17]
I would try 816, 813 (to confirm), and 8l0. If they group, pick the longer one to allow for throat wear.
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Posted: 5/16/2022 9:32:06 PM EDT
[#18]
If using tangent ogive, it'll shoot well with an inch of jump or more until the throat roughness increases BC variation.
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Posted: 5/17/2022 7:12:35 AM EDT
[#19]
Failed to mention that this test was shot round robin style.
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Posted: 7/15/2022 12:22:37 PM EDT
[#20]
Nm...
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Posted: 7/15/2022 8:02:35 PM EDT
[#21]
Quoted: From left to right: 2.832, 2.813, 2.803, 2.791, 2.781. These are OAL, I have the BTO in my notes on each one. |
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Posted: 7/15/2022 11:29:23 PM EDT
[#22]
Quote HistoryQuoted: I'm wondering why the from one COAL to the next is not the same or even some sort of "pattern" - 0.019, 0.010, 0.012, 0.010 !!! What's up with that??? |
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Posted: 7/16/2022 12:42:35 AM EDT
[#23]
I will offer a challenge to the OP.
You see, I believe they are all nearly identical with the dominant effect being influence from the shooter, overlaid here and there, obscuring the performance of the ammo; given that they are only 3 shot groups fired "round robin" (whatever that is). OP, did you call every shot? Did the impacts differ from your calls? OP, please post the BTO, as OAL can be misleading. What bullet is this? Did you crimp for the autoloader? If so, was it into a cannelure? |
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Posted: 7/16/2022 2:40:53 AM EDT
[#24]
There is a toy I have been lusting over but have not yet bought.
SCATT makes an optical sensor that will tell you where the barrel was pointed when the shot goes off. It is wireless, super-light weight, works out of doors and works with live fire. With that, you could measure the ammo on its own by deducting the shooter execution error from the point of impact. Add in a ShotMarker, that gives you point of impact and you have a pretty fancy shooting set up. (daydream mode is now off) |
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Posted: 7/16/2022 2:43:51 AM EDT
[#25]
Two more things -
Do it again. Even if you use 3 shot groups, just do it again. Do the results repeat? That was pretty darned good shooting, OP. |
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Posted: 7/16/2022 9:17:24 AM EDT
[#26]
Quote HistoryQuoted: I will offer a challenge to the OP. You see, I believe they are all nearly identical with the dominant effect being influence from the shooter, overlaid here and there, obscuring the performance of the ammo; given that they are only 3 shot groups fired "round robin" (whatever that is). OP, did you call every shot? Did the impacts differ from your calls? OP, please post the BTO, as OAL can be misleading. What bullet is this? Did you crimp for the autoloader? If so, was it into a cannelure? I did notice a slight shift in POI from POA from some of these seating depths, which very well could be barrel harmonics. At least that's my theory. 168 gr AMAX 2.830 BTO 2.201 2.813 BTO 2.184 2.803 BTO 2.174 2.791 BTO 2.164 2.781 BTO 2.154 Slight, maybe non existent crimp. To the post above asking about seating depth irregularities, I used BTO bc it's more accurate. But I wrote COL on the test bc it's easier to remember. |
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Posted: 7/16/2022 9:18:45 AM EDT
[#27]
Quote HistoryQuoted: There is a toy I have been lusting over but have not yet bought. SCATT makes an optical sensor that will tell you where the barrel was pointed when the shot goes off. It is wireless, super-light weight, works out of doors and works with live fire. With that, you could measure the ammo on its own by deducting the shooter execution error from the point of impact. Add in a ShotMarker, that gives you point of impact and you have a pretty fancy shooting set up. (daydream mode is now off) |
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Posted: 7/16/2022 9:29:50 AM EDT
[#28]
Quote HistoryQuoted: Two more things - Do it again. Even if you use 3 shot groups, just do it again. Do the results repeat? That was pretty darned good shooting, OP. The reason I did this seating depth test is bc the original load length I went with kept repeating at about 3/4 moa. I wanted to see if I could improve that at all with a seating depth test.   Went out after the seating depth test and confirmed the depth I wanted with a 4 shot group. I've noticed with this rifle, the first 2 shots are snake eyes to the right. But this is about as good as I can do, I'm probably done with it. |
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Posted: 7/16/2022 9:48:12 AM EDT
[#29]
Hey what app are you using to measure the group size?
I have a windows based one, but that looks much easier to use. B |
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Posted: 7/16/2022 10:00:25 AM EDT
[#30]
Quote HistoryQuoted: Hey what app are you using to measure the group size? I have a windows based one, but that looks much easier to use. B |
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Posted: 7/16/2022 10:24:27 AM EDT
[#31]
Quote HistoryQuoted: This is my vote as well. Quote HistoryQuoted: Quoted: Either 2 or 5. I would shoot 3 more 10 round groups with each of them and really see what is going on. This is my vote as well. This is how I always worked up a load. Once I had some promising loads I would shoot 10 round groups through the chronograph, it gave you a better idea of consistency. |
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Posted: 7/16/2022 4:39:28 PM EDT
[#32]
Nice shooting!
You seem to have an accuracy node at both the 2.8x and 2.7x lengths. There's also a slight possibility that there's a sweet spot between those two nodes. Maybe load three each at 2.790, 2.80, and 2.810 to see if your 2.813 and 2.781 lengths were "boxing in" an even tighter group. |
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Posted: 7/17/2022 1:51:46 AM EDT
[#33]
Quote HistoryQuoted: But this is about as good as I can do, I'm probably done with it. "A man has got to know his limitations."  |
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Posted: 7/17/2022 9:09:34 AM EDT
[#34]
Quote HistoryQuoted: Just based on that probably 2.81". Are the results repeatable? Do your groups tend the same way when you shoot 5 or 10 rd groups? This These tests are almost useless unless the groups are verified through multiple runs. What are your goals for the load, kill deer at 200, shoot steel at 600 or reaching out to 1000 just to try? Chasing that last bit for a deer load is wasting precious resources for zero gain. If you are doing it solely for the enjoyment of trying to get the smallest group then press on and have fun. That is a valid reason also. |
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