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Long Range Hunting & Shooting
Velocity increase on 6 month old ammo
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<blockquote data-quote="The Oregonian" data-source="post: 1643226" data-attributes="member: 51405"><p>I had maybe 30 extra rounds from hunting season last year....i hadn't shot that gun since then until a week ago, and had put it away clean. To my surprise, velocity jumped from 3010 avg to about 3070 avg. i cleaned the rifle again and used simichrome to check for carbon ring (there was none). I loaded down a grain with the same jar of powder (N560), same primers (F210), same brass, etc. temp wasn't really any different from my sessions last fall - all in the 60's and 70's at the same location.</p><p></p><p>Today I worked back up and got 3020 with the same powder charge on ammo that was loaded yesterday...I also shot 2 more of the old ammo and got 3070 again. No pressure signs the other day or today so I felt comfortable with those old rounds.</p><p></p><p>My guess is that brass springback is what led to the velocity increase...I go .003 under with a FL bushing and then .002 with a neck turning mandrel, so it could come back tighter over time. I anneal with AMP after each firing so the brass isn't worked hardened.</p><p></p><p>Nothing else changed...could it be springback? Or could it be bullet and neck getting sticky? I tumble with STM and then coat with graphite powder prior to neck expanding and thought that would cover any metal stickiness issue.</p><p></p><p>Gun is a 280AI with 168 hunting VLD's. Ammo has been kept inside where temp range is normal with heat and AC.</p></blockquote><p></p>
[QUOTE="The Oregonian, post: 1643226, member: 51405"] I had maybe 30 extra rounds from hunting season last year....i hadn’t shot that gun since then until a week ago, and had put it away clean. To my surprise, velocity jumped from 3010 avg to about 3070 avg. i cleaned the rifle again and used simichrome to check for carbon ring (there was none). I loaded down a grain with the same jar of powder (N560), same primers (F210), same brass, etc. temp wasn’t really any different from my sessions last fall - all in the 60’s and 70’s at the same location. Today I worked back up and got 3020 with the same powder charge on ammo that was loaded yesterday...I also shot 2 more of the old ammo and got 3070 again. No pressure signs the other day or today so I felt comfortable with those old rounds. My guess is that brass springback is what led to the velocity increase...I go .003 under with a FL bushing and then .002 with a neck turning mandrel, so it could come back tighter over time. I anneal with AMP after each firing so the brass isn’t worked hardened. Nothing else changed...could it be springback? Or could it be bullet and neck getting sticky? I tumble with STM and then coat with graphite powder prior to neck expanding and thought that would cover any metal stickiness issue. Gun is a 280AI with 168 hunting VLD’s. Ammo has been kept inside where temp range is normal with heat and AC. [/QUOTE]
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Velocity increase on 6 month old ammo
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