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Posted: 11/23/2012 1:09:40 PM EDT
| I have serveral ARs that I reload for and I have created my favorite "standard" load that I use in all of them using a Hornady 55 grain bullet and W748. I've also created many other loads for different bullets and different purposes with different powders that work well in individual rifles. Typically all of the different reloads vary little horizonally at impact, but they do vary vertically because of velocity and bullet BC. This is the case with all my ARs except one, a Colt HBAR with 1/9 barrel. I zero this Hbar with my favorite load, above, but all of the other reloads shoot 2-3 oclock and 4+ inches. Why is this barrel/rifle being so different from my others? |
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Quoted:
Another related question is why do some loads point of impact vary horizontally? This doesn't seem to happen very often and I'm guessing it's barrel harmonics, but I really don't know for sure. All of this is being done at 100 yards. This question bothered me also. I took two loads out to the range. They both were trimmed and loaded on the same equipment. Used the same primers, trimmer, cases and bullets. The only difference was in the powder. They were shot from the same rifle. You would expect only a vertical difference, wouldn't you? However there was a windage difference. On this particular morning when I did the shooting there was no wind to speak of. Like 0-3 MPH. I asked the club President why the horizontal difference. This guy knows his stuff. He is a master at the shooting skills. He was was in charge of the Marine competition shooting team for many years, taught Olympic competitors and FBI snipers. Has won Camp Perry and has more state and individual shooting championships that you can count. He has been reloading for over 40 years. His answer was "I don't know, probably due to the different burn rates affecting the harmonics of the barrel". He says that is one of the great mysteries of the shooting world. |
| Thanks Flash! And my HBAR is shooting variations of elevation and horizontal displacement at the 2 oclock position. What's odd about the HBAR is that is doesn't like my "standard" load, but likes everything else, but all my other ARs love my "standard" load. Go figure... |
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Quoted:
The longer the barrel the more harmonics that are going to come into play. I can take the same exact load and shoot it from a 20" barrel, and a 24" barrel, and the shot is almost always horizontally different. May not be much, but it is different. I was hoping the HBAR, with heavy barrel, would be immune to this "harmonic" problem. |
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Even a 50BMG barrel moves when it is fired. It all comes down to Harmonics. Youtube some slow motion barrel shooting and watch the barrels when they are fried. I would hot link some but I am at work and they block Youtube.
MAHA Try "High-speed video of scope and barrel flexing on a 50BMG" in youtube. |
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