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sudden velocity increase mystery
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<blockquote data-quote="Robbin" data-source="post: 395930" data-attributes="member: 12246"><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">Got an interesting problem. 2 months ago I shot a ten shot string, got a solid MV average, which confirmed my previous shooting and ordered a custom dial. I've had the dial a month, but haven't had time to shoot. My step son showed up for a weekend shoot, and his CED crony consistently showed that rifle over 100 FPS faster. I assumed it was just a different crony, but at 800 yards, the dial was very high. I went home, got my crony and it's average velocity was within 5fps of my step sons. The rifle has 200 rounds thru it, so it should be about broke in. It shot very well, 4.5 inch 3 shot groups at 800 with an 8 pound encore, so I'm tickled pink! But where did the solid 100FPS+ velocity increase come from. </span></span></p><p> </p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">The brass is neck sized only, 4th firing. The only difference is I annealed it before this firing. </span></span></p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">Primers are the same out of the same batch. CCI 450 </span></span></p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">Powder is RL 17 same 5 pound jug. Every round measured to the .1 charge.</span></span></p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">NEW batch of Berger 140 VLDs (6.5X47 lapua, neck turn .290 neck) MOLY coated</span></span></p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">Bullets loaded long, final seating done by when chambered on both guns. </span></span></p><p> </p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">Shooting in Florida, it's warmer now than it was 2 months ago, but not by a large difference. Upper 80s vs upper 70s.</span></span></p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">We used a sun shade this time so the gun and ammo were NOT sitting in the sun. </span></span></p><p> </p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">NOW HERE IS THE KICKER, I lowered my favorite load by .4 grains because I've gotten uncomfortable with the sticky bolt or in this case sticky opening of the frame. </span></span></p><p> </p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">My bench gun shoots the EXACT same round (both guns built with the same reamer) it showed an increase of about 8 fps, which I attribute to the higher temps. </span></span></p><p> </p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">So where did the 105FPS of MV come from WITHOUT getting my sticky bolt back. I'm shooting 105FPS faster with less powder and no sticky bolt that I was getting when the gun was shooting 100FPS slower? If it came from temps, why didn't my bench gun that shoots the exact same round show the increase? So two guns, shooting the exact same round, I don't even separate the brass, or the loaded rounds, I use them in both guns. </span></span></p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">One shows an 8FPS increase one shows 105FPS increase. If the higher temps made the powder burn hotter, it would have increased my pressure and my sticky bolt would have returned with a vengeance….</span></span></p><p> </p><p><span style="font-size: 12px"><span style="font-family: 'Calibri'">Interesting stuff, I'd like to hear your ideas…</span></span></p></blockquote><p></p>
[QUOTE="Robbin, post: 395930, member: 12246"] [SIZE=3][FONT=Calibri]Got an interesting problem. 2 months ago I shot a ten shot string, got a solid MV average, which confirmed my previous shooting and ordered a custom dial. I’ve had the dial a month, but haven’t had time to shoot. My step son showed up for a weekend shoot, and his CED crony consistently showed that rifle over 100 FPS faster. I assumed it was just a different crony, but at 800 yards, the dial was very high. I went home, got my crony and it’s average velocity was within 5fps of my step sons. The rifle has 200 rounds thru it, so it should be about broke in. It shot very well, 4.5 inch 3 shot groups at 800 with an 8 pound encore, so I’m tickled pink! But where did the solid 100FPS+ velocity increase come from. [/FONT][/SIZE] [FONT=Calibri][SIZE=3] [/SIZE][/FONT] [SIZE=3][FONT=Calibri]The brass is neck sized only, 4th firing. The only difference is I annealed it before this firing. [/FONT][/SIZE] [SIZE=3][FONT=Calibri]Primers are the same out of the same batch. CCI 450 [/FONT][/SIZE] [SIZE=3][FONT=Calibri]Powder is RL 17 same 5 pound jug. Every round measured to the .1 charge.[/FONT][/SIZE] [SIZE=3][FONT=Calibri]NEW batch of Berger 140 VLDs (6.5X47 lapua, neck turn .290 neck) MOLY coated[/FONT][/SIZE] [SIZE=3][FONT=Calibri]Bullets loaded long, final seating done by when chambered on both guns. [/FONT][/SIZE] [FONT=Calibri][SIZE=3] [/SIZE][/FONT] [SIZE=3][FONT=Calibri]Shooting in Florida, it’s warmer now than it was 2 months ago, but not by a large difference. Upper 80s vs upper 70s.[/FONT][/SIZE] [SIZE=3][FONT=Calibri]We used a sun shade this time so the gun and ammo were NOT sitting in the sun. [/FONT][/SIZE] [FONT=Calibri][SIZE=3] [/SIZE][/FONT] [SIZE=3][FONT=Calibri]NOW HERE IS THE KICKER, I lowered my favorite load by .4 grains because I’ve gotten uncomfortable with the sticky bolt or in this case sticky opening of the frame. [/FONT][/SIZE] [FONT=Calibri][SIZE=3] [/SIZE][/FONT] [SIZE=3][FONT=Calibri]My bench gun shoots the EXACT same round (both guns built with the same reamer) it showed an increase of about 8 fps, which I attribute to the higher temps. [/FONT][/SIZE] [FONT=Calibri][SIZE=3] [/SIZE][/FONT] [SIZE=3][FONT=Calibri]So where did the 105FPS of MV come from WITHOUT getting my sticky bolt back. I’m shooting 105FPS faster with less powder and no sticky bolt that I was getting when the gun was shooting 100FPS slower? If it came from temps, why didn’t my bench gun that shoots the exact same round show the increase? So two guns, shooting the exact same round, I don’t even separate the brass, or the loaded rounds, I use them in both guns. [/FONT][/SIZE] [SIZE=3][FONT=Calibri]One shows an 8FPS increase one shows 105FPS increase. If the higher temps made the powder burn hotter, it would have increased my pressure and my sticky bolt would have returned with a vengeance….[/FONT][/SIZE] [FONT=Calibri][SIZE=3] [/SIZE][/FONT] [SIZE=3][FONT=Calibri]Interesting stuff, I’d like to hear your ideas…[/FONT][/SIZE] [/QUOTE]
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