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Old April 27, 2012, 06:58 AM   #1
rebs
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group moved with a change in powder charge

I loaded 3 different loads for my S&W Sport with all using the same bullet, brand of case and primer. I used H335 powder with three different charges, 23.5 grs, 24.5 grs and 25.5 grs. The 23.5 didn't put one shot on the paper, the 24.5 posted a 1" group right on the right edge of the paper and the 25.5 was just off the right edge of the paper, so I didn't get a good look at the group as there was other peoples holes in the target holder.
Why did the group move to the right with a different powder charge ?
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Old April 27, 2012, 07:04 AM   #2
Don P
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Perhaps its the shooter. Possibility is all I'm pointing out.
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Old April 27, 2012, 08:36 AM   #3
SonOfGun
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No 2 loads perform the same. Why would you assume they are going to have same POI? Each load has its own harmonics and will exit the barrel different. Keep trying different combinations untill you find what your rifle likes. If you fired THAT load in another rifle POI will change. It is a never ending quest for perfection.
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Old April 27, 2012, 09:24 AM   #4
Unclenick
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It's normal to get some vertical stringing due to the different loads having a different bullet barrel times and exiting when the muzzle whip is in a different position. Having it happen horizontally, though, means the muzzle is moving horizontally, and that could be just due to the butt not being squarely in your shoulder so the gun moves with recoil. If you are left-handed, having shots move right as the butt slips left would be a possibility. Another possibility is some kind of uneven stock pressure on the barrel influencing muzzle position. You may have to float the front handguard to clear that. Any book on match accurizing AR's will show how that's done. I can't say I've seen it on a 16" barrel, personally, but I don't know why it couldn't be done.
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Old April 27, 2012, 03:31 PM   #5
oneoldsap
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Different loads generate different barrel harmonics . Your POI could move in any direction , it's the size of the group that's important , the POI can be adjusted to point of aim !
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Old April 27, 2012, 04:34 PM   #6
Unclenick
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I've had groups open up and shrink as well as moving vertically due to barrel time changes, and even go diagonal in gusting wind, but any horizontal stringing I've seen has always proved to be traceable to an addressable cause. Not counting shooter position issues, I've seen it where bolt lugs needed lapping because they were only making solid contact on one side, or where the inletting favored one side, and of course there's asymmetrical front stock contact with the barrel. A barrel that needed stress relieving will sometimes walk to the side as it heats, but that doesn't normally produce round groups. I still expect there will be something for him to identify that he can change.
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Old April 27, 2012, 04:42 PM   #7
Strafer Gott
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What's the target range? I've been using comparable loads of H335 with a NATO barreled Colt Sporter, 24.5grs to be precise, with good results.
Load like that and adjust your sights. You probably are experiencing a little barrel whip. That 1" group is pretty good, and adjusting sights is easier than chasing a load. I've tried other powders, but come right back to H335.
Are you using a sling?
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Old April 27, 2012, 06:28 PM   #8
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as mentioned--what range? wind direction and velocity? Sounds like some sights/scope zeroing was reqired? how many shots in a "group?" what kind of rest was used? was the bench stable? was the shooter stable? were there horses in the stable? Was there a dog in the manger? Inquiring minds want to know...........
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