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Posted: 7/2/2008 6:04:20 PM EDT
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Finally made it to the range today to try some test loads for my RRA 5.56 Wylde Chamber, 20", 1x8twist NM rifle. I was using virgin Guat brass from Wideners, CCI small BR primers, 77gr SMK bullet loaded to 2.260" COAL. I've tried this last year and shot all 20 rounds on the same target and couldn't tell which hole was from each shot, so I decided to use 2 targets with 10 shots at each. Range conditions 1570ft elevation, 83deg F. Was shooting at 200 yards and in the mountains I live in, the 200yd line is ~55ft higher than the firing line according to the GPS. Since I had problems last time I did this, I was going to take a picture through the scope after each shot. I tried it before I started, and I didn't think it was going to work well so did not continue. This shot is either at 9x or 26x (low/high power of my scope.) Anybody know how to do the math with the mil dots to tell me if it was 9x or 26x? The black circle of the target is 8" in diameter. In the picture below, the first 10 were on the left hand target, the middle target was an old one I used to make sure my scope was still sighted, last 10 shots on the right hand target (not visible)  I shot 3 rounds to make sure my scope was close, then shot 20 rounds with 90 to 120 seconds between rounds. I put one round in the magazine and used the bolt latch to close the bolt. The first round was 22.3 grains TAC, used a 0.1grain increment, the 20th round was 24.2 grains TAC (warning, that is 0.2 grains above Sierra's max!) I saw no obvious signs of high pressure. First 10 shots (22.3 to 23.2 grains) looked like this  Second 10 shots (23.3 to 24.2 grains) looked like this  (shots 1 and 5 could be reversed, but I don't think that would be a biggie) I'm thinking my best bet is to go with 23.5 grains of TAC which is #3 on the 2nd target. My reason is shots 1,2,3,4 & 5 on that target stayed within 0.75" in elevation from each other and gives me a 0.2grain leeway on either side for a progressive press. (Don't have one yet, these were loaded on a single station RCBS with each round trickled weighed.) It's also not near the recommended max which will make it easier on my brass and rifle. Am I looking at this correctly? What load would you use? TIA TD |
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Mil Dot was confusing to me at first try www.mil-dot.com/ BTW good shooting. Still waiting to loadmy fIrst rounds. Some more equipment and homework first. |
Thanks, that helped. I knew the math, but I didn't know my scope should have the mildots correct at max power (probably). I guess I'll have to do the 4" barber pole at 111yds to check. |
| Not sure why you only loaded 1 round with each charge weight. If you are looking to get to a desired speed, then I guess that is ok. If you want to find out what charge will give you the best group, then you need to load 5 or 10 rounds per charge weight and shoot for groups. |
That's not how a ladder test works. You put together an ascending (or descending) charge weight and look for several different weights to go into a group close together. You end up (usually) with a vertically strung group but with some shots being closer together than others, forming sub-groups within the larger group. I've tried it and that's how I arrived at my load for my M1A. It works best at extended distances. From what I see here, It looks like it kinda shoots everything pretty well. Based on what I see, I'd take the hottest load I tried that didn't show pressure, and then load 5-10 rounds and shoot for a group with that. ETA: Looking at it again, I'd go with 3,4, and 5 off of the latter target. 23.5-23.7 grains? |
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0.1 gr betweeen loads is pretty tight, you might not be getting enough variation to see a pattern, apart form shooter error, wind, gravity waves, etc. (good shooting BTW) Can you reshoot at 300 yards? Try something like 10 loads with a 0.2gr jump, or maybe 8 loads with a 0.3 jump, and see if you get a definite pattern. Also, load 2 of each, and shoot at 2 targets- -shoot light load up on one target, then heavy load down on the second target. Then lay the targets over each other, and see what you got. I usually shoot 10 individual targets with 3 shots each, then lay the targets over each other, and look for concurrent loads that are cutting the same group- -kind of what your trying to do with a ladder test, but shooting a lot more obviously. When starting with a new load, I shoot 1 shot at each target going up the load weight, and stop if I get pressure signs. If none, I shoot the rest. |
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Use 0.3 grain increments and shoot all shots on the same target. You'll never find a tuned load by overlaying targets, at least not very easily. You also need a rudimentary wind flag such as a piece of surveyor tape set out about 1/3 of the distance to the target. Understanding the called shots for gun handling or wind is critical. 0.1 grain load increments will shoot your barrel out before you find a good load for more than one or two bullets. Also, shoot at least one fouling round before starting a test string. A little experimentation and observation is needed to determine the number of foulers is needed. You're seeking an increment of loads that fall nearly on top of each over and produce the smallest group, say from 23.3 to 23.9 grains (a typical example for .223 Rem loads, not for the charges you are shooting). This will be a robust load that can suffer typical measure charge variation without affecting accuracy. Or safety. |
Correct, shot 3=23.5gr, 4=23.6, 5=23.7gr. I'd set my powder measure at 23.6.
Unfortunately not. At this range 300 yards will be 100 yards up in elevation + will have to shoot through trees. That and I can't see that far anymore.
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The ladder can very often be inconclusive. Try this instead: www.twincityrodandgun.com/PDF%20files/Dan%20Newberry%20-%20OCW.pdf |
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