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Max Online: 16728 @ 03/25/12 08:51 AM
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#5926140 - 09/13/15 08:10 AM SD of 29 and velocity all over the place?
wp75169 Offline
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Registered: 10/11/09
Posts: 3874
Loc: Wills Point
I ran my first 5 rounds through a chronograph yesterday to get my speed. The minimum and max were over 100 feet apart and the SD was 29. Average speed was 2577. This was also the first 5 rounds after cleaning the barrel so they were fouling rounds. I'm hoping this was just because of the cleaning/fouling because I am fairly confident that's the most consistent loads I can make. The gun shot good in my opinion. Later in the day I dialed wrong and missed 3 in a row at 600 yards so we drove down to see where I was hitting. The results would lead me to believe the speed leveled out. Here is my miss around shot 35ish for the day at 600.


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#5926177 - 09/13/15 08:43 AM Re: SD of 29 and velocity all over the place? [Re: wp75169]
RiverRider Online   content
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Registered: 11/11/07
Posts: 6691
Loc: Wise Co.
It's pretty obvious to me that your barrel needed to be fouled before it would settle down. And I'd say it settled down very nicely!
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#5926203 - 09/13/15 09:14 AM Re: SD of 29 and velocity all over the place? [Re: wp75169]
FiremanJG Online   content
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Registered: 12/16/08
Posts: 19222
Loc: Wolfe City, TX
What cartridge? Brass, primer, powder, bullet? Virgin brass?
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#5926215 - 09/13/15 09:27 AM Re: SD of 29 and velocity all over the place? [Re: FiremanJG]
wp75169 Offline
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Registered: 10/11/09
Posts: 3874
Loc: Wills Point
Originally Posted By: FiremanJG
What cartridge? Brass, primer, powder, bullet? Virgin brass?


7-08, nosler, Remington 9.5, varget 39.8, 162 Amax, once fired FL sized.

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#5926224 - 09/13/15 09:32 AM Re: SD of 29 and velocity all over the place? [Re: wp75169]
FiremanJG Online   content
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Registered: 12/16/08
Posts: 19222
Loc: Wolfe City, TX
It obviously started shooting once it got fouled, no surprise there.

Did you chronograph the shots after it was fouled or only on the beginning rounds? Your powder charge and bullet weight ae the same load as my 7-08.
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#5926236 - 09/13/15 09:39 AM Re: SD of 29 and velocity all over the place? [Re: wp75169]
wp75169 Offline
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Registered: 10/11/09
Posts: 3874
Loc: Wills Point
Unfortunately I did not check any after it got fouled. There was several people shooting and the clamp on chronograph cause a POI change so it would have been a time and bullet consumer.

As far as same load as yours if I remember correctly it's the same obermyer 5R barrel.


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#5926272 - 09/13/15 10:05 AM Re: SD of 29 and velocity all over the place? [Re: wp75169]
FiremanJG Online   content
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Registered: 12/16/08
Posts: 19222
Loc: Wolfe City, TX
I believe they are the same barrel. I cut mine down to 20" and it always wears a suppresor.

I bet if you chronoed 5 rounds next trip out the numbers will look better.
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#5926310 - 09/13/15 10:45 AM Re: SD of 29 and velocity all over the place? [Re: wp75169]
Cleric Online   content
Veteran Tracker

Registered: 03/11/12
Posts: 2767
I am having trouble with your math....

assuming an average of 2577, spread of 100 i can't get a stand dev below 35... and thats at ideal mathematical conidtions

Shot 1: 2577
Shot 2: 2627 (Avg +50)
Shot 3: 2527 (Avg-50)
Shot 4: 2578 (Avg +1)
Shot 5: 2577 (Avg -1)

This would mean that the min/max were perfectly centered and the other two shots were within 1 fps

Do you have your actual 5 numbers?

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#5926389 - 09/13/15 11:43 AM Re: SD of 29 and velocity all over the place? [Re: wp75169]
wp75169 Offline
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Registered: 10/11/09
Posts: 3874
Loc: Wills Point
Nope. Just read the numbers and went with the average. It's not my math at all but that of the chronograph. I did not write down each speed. I do know one was in the 24xx and one was 26xx. Hence my statement over 100 ft. I may have shot more than 5 rounds and could explain the math. I was generalizing on the 5 rounds. I should have said 5 ish. Two people there are members here and one of them owns the magneto I was using. Maybe they can chime in with a better memory or the actual #s off the graph.

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#5927604 - 09/14/15 07:21 AM Re: SD of 29 and velocity all over the place? [Re: wp75169]
ChadTRG42 Offline
THF Celebrity

Registered: 09/16/09
Posts: 10257
Loc: Lewisville, TX
Remember my thread on cleaning and fouling shots? Your high ES numbers are from the cleaning and such. With a 1.5" group at 600 yards, just keep shooting it, you're fine.
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#5927971 - 09/14/15 11:41 AM Re: SD of 29 and velocity all over the place? [Re: wp75169]
6.5x47Lapua Offline
Tracker

Registered: 12/13/14
Posts: 518
Loc: dfw
Another reason to leave the chronograph at home where it belongs. Hits and down range results are all that matter.

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