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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Quick question, root cause of 2 + 1 groups?
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<blockquote data-quote="emp1953" data-source="post: 2629993" data-attributes="member: 71817"><p>I have a Sig970SHR in .270win and a Cooper in .270win. They both will give me groups like this. As the barrel heats up it gets more pronounced. Its a hunting rifle and it is what I expect. If I let it cool between shots, bolt open, 10 minutes they all touch. I did it once with a 10 shot group, it wasted a lot of time nearly 2 hours but proved a point. When allowed to cool the rifles both printed nearly the same hole over and over again. When I see weird stuff going on I will usually start by single feeding each round rather then shoot from the magazine. I've found certain lots of brass exhibit decreasing neck tension after the 3rd or 4th reloading allowing the bullets to jump forward during recoil. This changes internal case volume, which effects velocity and changes bullet jump distance to the lands, all of which will change POI.</p></blockquote><p></p>
[QUOTE="emp1953, post: 2629993, member: 71817"] I have a Sig970SHR in .270win and a Cooper in .270win. They both will give me groups like this. As the barrel heats up it gets more pronounced. Its a hunting rifle and it is what I expect. If I let it cool between shots, bolt open, 10 minutes they all touch. I did it once with a 10 shot group, it wasted a lot of time nearly 2 hours but proved a point. When allowed to cool the rifles both printed nearly the same hole over and over again. When I see weird stuff going on I will usually start by single feeding each round rather then shoot from the magazine. I've found certain lots of brass exhibit decreasing neck tension after the 3rd or 4th reloading allowing the bullets to jump forward during recoil. This changes internal case volume, which effects velocity and changes bullet jump distance to the lands, all of which will change POI. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Quick question, root cause of 2 + 1 groups?
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