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Posted: 7/28/2013 8:52:19 AM EDT
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I've read the instructions many times, and have done a few tests, but I still have one question.
I realize there are many variables when interpreting the results of a OCW test. I'd like to get some clarification on this one issue. Can you generalize the vertical or horizontal stringing of a group (assume group size is basically the same) to say that one pattern is better than another? In other words, would I prefer to see a group like * * * or * * * Rem 700, 168 SMK, IMR4064. 
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I had Dan Newberry interpret mine. The groups of three rnds progressively got smaller until I came to a scatter node (a point where the group opened up considerably). I believe at
that point he multiplied that group charge by a factor of 1.5% plus that charge weight to come up with an ocw. You also have to look to see that the center of each charge weight fell close to the same poi for two or three groups. If you need help, I would suggest going to his site, post your targets and ask. Here's my post. http://practicalrifler.fr.yuku.com/topic/2200/OCW-for-223-77gr-SMK-and-Varget#.UfVayKy2_ag |
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Do yourself a favor. Shoot a group of 20 rounds. Do it at a reasonable distance - 100 to 200 yards. Use a target that is easy to aim at (typically not a big black disk). That group will define for everyone (you and us) what your shooting system is capable of delivering, so take your time and shoot it as well as possible.
When you shoot that group, call and record all your shots. Keep written records of the wind speed & direction for every shot. Correlate the wind info to the point of impact. When you've finished, you are ready to think about shooting the ladder. Bring photos of that group and your ladder results here. We can better help you that way. I hope this helps. It's all about setting expectations. Federal Gold Medal Match is a good ammo if you can find it to buy. If you reload, try this recipe (or something similar that is a known-good load): 42 gr IMR4064 Winchester case Federal 210M primer <- DOH! fixed it 168 MatchKing (seated to magazine length) |
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The goal of the OCW is to use a round robin test to find the load range that is the least sensitive to small changes, then select the middle of that range as the optimal charge weight.
There are some assumptions with this statement. One is that the horizontal spread is windage and not really a bad characteristic in your rig. Another is that the groups used to find those group centers are not huge. The down side of those outcomes is that if they are really bad characteristics in your combination of gun and ammo, you will likely not be happy with the center of the load range no matter how flat the velocity and vertical spread of that load comes out. Generally, those two things don't happen too often, and the stable node is both the best for vertical as well as horizontal. What you are looking for is that stable node where changes on the order of 0.25 grains, either way, won't open the group or significantly shift the POI. |
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Quoted:
Do yourself a favor. Shoot a group of 20 rounds. Do it a reasonable distance - 100 to 200 yards. Use a target that is easy to aim at (typically not a big black disk). That group will define for everyone (you and us) what your shooting system is capable of delivering, so take your time and shoot it as well as possible. When you shoot that group, call and record all your shots. Keep written records of the wind speed & direction for every shot. Correlate the wind info to the point of impact. When you've finished, you are ready to think about shooting the ladder. Bring photos of that group and your ladder results here. We can better help you that way. I hope this helps. It's all about setting expectations. Federal Gold Medal Match is a good ammo if you can find it to buy. If you reload, try this recipe (or something similar that is a known-good load): 42 gr IMR4064 Winchester case Winchester Small Rifle Primer 168 MatchKing (seated to magazine length) Hmm... Make sure he knows this is only for palma brass. :-) |
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Hmm... Make sure he knows this is only for palma brass. :-) Huh? The issue behind the recommendations I made is that groups should be more or less round, unless you are having trouble with the wind. Everyone has trouble with wind, so the groups will be strung horizontally, at least a bit. The other issue for interpreting OCW groups is that often the small differences between loads gets swallowed up by the larger variations in POI - your minimum average group size, as determined by the shooting system (shooter, rifle, ammo and conditions). For example, let's say you're shooting at 200 yards. Your next load increment is responsible for an additional 1/4" more drop. You may not be able to detect that reliably if you're only able to shoot to 1/2, 3/4 or 1 MOA. That's because your groups will be one to two inches in diameter and the POI only changed by 1/4". So, when you shoot the next round and it lands 3/4" high but should have been 1/4" lower - what does that mean? How do you interpret that result? This is THE problem with experiments that use small sample sizes and it's exacerbated by the poor signal to noise ratio. By the way, how many of you can really shoot 1 MOA all day long? That's 2" at 200 yards. If you're shooting 2" groups, can you reliably detect a 1/4" change in drop caused by your ammo when you fire only (approximately) 3 rounds? |
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To me having droups spread vertically means that the load isn't consistent. There is a variation in velocity causing the spread. A horizontal group could be due to wind. If I had to choose I would prefer the horizontal spread instead of the vertical. This.... And this is why horizontal stringing is ignored in a ladder test to find an accuracy node(s). |
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This.... And this is why horizontal stringing is ignored in a ladder test to find an accuracy node(s). Quoted:
Quoted:
To me having droups spread vertically means that the load isn't consistent. There is a variation in velocity causing the spread. A horizontal group could be due to wind. If I had to choose I would prefer the horizontal spread instead of the vertical. This.... And this is why horizontal stringing is ignored in a ladder test to find an accuracy node(s). I'm not following you're last comment, to me it seems contrary to what you quoted above. Thanks for the replies, they have helped out a lot. |
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I'm not following you're last comment, to me it seems contrary to what you quoted above. Thanks for the replies, they have helped out a lot. When running a ladder test to find your gun's accuracy nodes, windage is/can be ignored. It's the vertical stringing that shooters try to eliminate. Windage is usually shooter error, or external ballistics. |
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I'm not following you're last comment, to me it seems contrary to what you quoted above. Thanks for the replies, they have helped out a lot. Quoted:
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To me having droups spread vertically means that the load isn't consistent. There is a variation in velocity causing the spread. A horizontal group could be due to wind. If I had to choose I would prefer the horizontal spread instead of the vertical. This.... And this is why horizontal stringing is ignored in a ladder test to find an accuracy node(s). I'm not following you're last comment, to me it seems contrary to what you quoted above. Thanks for the replies, they have helped out a lot. When I do ladder tests, I always chronograph every round. That way, I can correlate the changing POI to velocity. As they speed up, they should impact progressively higher on the target. |
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When I do ladder tests, I always chronograph every round. That way, I can correlate the changing POI to velocity. As they speed up, they should impact progressively higher on the target. What distance do you shoot the test? I've read that the farther, the better. |
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When I do ladder tests, I always chronograph every round. That way, I can correlate the changing POI to velocity. As they speed up, they should impact progressively higher on the target. Quoted:
Quoted:
Quoted:
Quoted:
To me having droups spread vertically means that the load isn't consistent. There is a variation in velocity causing the spread. A horizontal group could be due to wind. If I had to choose I would prefer the horizontal spread instead of the vertical. This.... And this is why horizontal stringing is ignored in a ladder test to find an accuracy node(s). I'm not following you're last comment, to me it seems contrary to what you quoted above. Thanks for the replies, they have helped out a lot. When I do ladder tests, I always chronograph every round. That way, I can correlate the changing POI to velocity. As they speed up, they should impact progressively higher on the target. Unless you are shooting a handgun, where the faster rounds hit lower. I have given people brain cramps trying to explain that. |
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What distance do you shoot the test? I've read that the farther, the better. Quoted:
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When I do ladder tests, I always chronograph every round. That way, I can correlate the changing POI to velocity. As they speed up, they should impact progressively higher on the target. What distance do you shoot the test? I've read that the farther, the better. Personally, I shoot at 200 yards. At 200 yards, I can see each and every shot. I've tried 300 yards but it is almost impossible to see the holes and I just can't bring myself to shoot an important group and not see the holes. Ditto for 600 yards. For anything longer than 200 yards, you really need to have two people - one in the pits and one shooting. Two people during load development is a rarity. |
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Personally, I shoot at 200 yards. At 200 yards, I can see each and every shot. I've tried 300 yards but it is almost impossible to see the holes and I just can't bring myself to shoot an important group and not see the holes. Ditto for 600 yards. For anything longer than 200 yards, you really need to have two people - one in the pits and one shooting. Two people during load development is a rarity. Quoted:
Quoted:
Quoted:
When I do ladder tests, I always chronograph every round. That way, I can correlate the changing POI to velocity. As they speed up, they should impact progressively higher on the target. What distance do you shoot the test? I've read that the farther, the better. Personally, I shoot at 200 yards. At 200 yards, I can see each and every shot. I've tried 300 yards but it is almost impossible to see the holes and I just can't bring myself to shoot an important group and not see the holes. Ditto for 600 yards. For anything longer than 200 yards, you really need to have two people - one in the pits and one shooting. Two people during load development is a rarity. Yeah. It's really hard to talk someone into going downrange and watching for bullet holes. 
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When running a ladder test to find your gun's accuracy nodes, windage is/can be ignored. It's the vertical stringing that shooters try to eliminate. Windage is usually shooter error, or external ballistics. Quoted:
Quoted:
I'm not following you're last comment, to me it seems contrary to what you quoted above. Thanks for the replies, they have helped out a lot. When running a ladder test to find your gun's accuracy nodes, windage is/can be ignored. It's the vertical stringing that shooters try to eliminate. Windage is usually shooter error, or external ballistics. This is what I thought when I started this thread. I just wanted to get some validation. Thank you to everyone who has said the same. /thread.
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Try this http://www.6mmbr.com/laddertest.html
Like others have suggested it ignores the horizontal separation of each shot. You really want to do this test at 200 yards like it says, otherwise it will be hard to interpret. |
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Huh? The issue behind the recommendations I made is that groups should be more or less round, unless you are having trouble with the wind. Everyone has trouble with wind, so the groups will be strung horizontally, at least a bit. The other issue for interpreting OCW groups is that often the small differences between loads gets swallowed up by the larger variations in POI - your minimum average group size, as determined by the shooting system (shooter, rifle, ammo and conditions). For example, let's say you're shooting at 200 yards. Your next load increment is responsible for an additional 1/4" more drop. You may not be able to detect that reliably if you're only able to shoot to 1/2, 3/4 or 1 MOA. That's because your groups will be one to two inches in diameter and the POI only changed by 1/4". So, when you shoot the next round and it lands 3/4" high but should have been 1/4" lower - what does that mean? How do you interpret that result? This is THE problem with experiments that use small sample sizes and it's exacerbated by the poor signal to noise ratio. By the way, how many of you can really shoot 1 MOA all day long? That's 2" at 200 yards. If you're shooting 2" groups, can you reliably detect a 1/4" change in drop caused by your ammo when you fire only (approximately) 3 rounds? Quoted:
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Hmm... Make sure he knows this is only for palma brass. :-) Huh? The issue behind the recommendations I made is that groups should be more or less round, unless you are having trouble with the wind. Everyone has trouble with wind, so the groups will be strung horizontally, at least a bit. The other issue for interpreting OCW groups is that often the small differences between loads gets swallowed up by the larger variations in POI - your minimum average group size, as determined by the shooting system (shooter, rifle, ammo and conditions). For example, let's say you're shooting at 200 yards. Your next load increment is responsible for an additional 1/4" more drop. You may not be able to detect that reliably if you're only able to shoot to 1/2, 3/4 or 1 MOA. That's because your groups will be one to two inches in diameter and the POI only changed by 1/4". So, when you shoot the next round and it lands 3/4" high but should have been 1/4" lower - what does that mean? How do you interpret that result? This is THE problem with experiments that use small sample sizes and it's exacerbated by the poor signal to noise ratio. By the way, how many of you can really shoot 1 MOA all day long? That's 2" at 200 yards. If you're shooting 2" groups, can you reliably detect a 1/4" change in drop caused by your ammo when you fire only (approximately) 3 rounds? Trollslayer....I think the "palma brass" comment was about your load using a small rifle primer, that's all. |
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Trollslayer....I think the "palma brass" comment was about your load using a small rifle primer, that's all. DOH!
I fixed it. Too much posting about 223 cartridges - I meant to post Federal 210M primers (large rifle) but the brain went into autopilot and the fingers took over. |
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