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What the heck is goin on?

 
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  #8  
Old 08-29-2005, 10:05 PM
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Location: Sask. Canada
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Re: What the heck is goin on?

I would not worry about the numbers until you get some good data from your new machine. You are probably in a learning curve if this is your first Oehler and you might run a search for info on setting up Oehlers since we have covered that extensively. I use a laser to setup my screens, works great and saves time. Good luck with your new toy, you picked the best.

By the way, black and yellow pieces flying through your scope picture is not good when you are shooting through Oehlers [img]/ubbthreads/images/graemlins/smirk.gif[/img] I been there so many times I can rebuild skyscreens blindfolded.
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  #9  
Old 08-30-2005, 09:03 AM
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Re: What the heck is goin on?

[ QUOTE ]
I second what Ian said.

3 feet is WAY to close to the muzzle to get an accurate reading. It states that in the destruction manual.

[/ QUOTE ]

+1...no...+10!!

with the bigger case, 15feet wont hurt either [img]/ubbthreads/images/graemlins/wink.gif[/img]

JB
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  #10  
Old 08-30-2005, 08:04 PM
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Re: What the heck is goin on?

Let's see if recent experience agrees with yours. Using JBM ballistic software too and hornady bullets. With their listed BC or just mucking about, not even close. All scope adjustments retested and verified on a measured surface so I know that part is right.

Solution...which G function are you using? G1? If so, the data the program spits out is completely wrong.

With a 162gr Amax, I had to use the G7 profile and got within 2 clicks out to 650yds. Close enough for me.

So the BC debate can continue to rage. A 0.65 G7 BC is way higher then a G1 0.65 BC. I now just enter what I field data then change the G function until I get something that is close.

If three points are close, the rest of the data will also work out.

Honestly, don't care which G function I end up with. I just want a drop table that works for my load.

Jerry
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  #11  
Old 08-30-2005, 10:03 PM
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Re: What the heck is goin on?

T.O.,
do you by chance play in eastern PA. if so quit jacking us around,and tell us what your agenda is.
UB
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  #12  
Old 08-30-2005, 10:04 PM
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Re: What the heck is goin on?

additionally, lets not forget that by using the same chronograph at both ranges, and consequently comparing average velocity of rounds fired at each range, you are effectively building the ES of your load into the accuracy of your BC measuring. Just something to think about.
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  #13  
Old 08-31-2005, 03:54 PM
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Re: What the heck is goin on?

Nope don't live anywhere Eastern USA. About as far west in CANADA as can get without getting wet. So no, I do not BS and have no agenda except sharing experiences through burning powder. I think they refer to that as real world experience.

I wonder what Eastern American agenda might be anyways? Want to elaborate????

Speaking of which, I went out and reshot my drop chart as I do just to make sure everything is right for hunting season.

Using the data generated by the JBM software, my drops at 5 distances were within 1 click (furthest one was off by 1 click) of predicted data. Ranges were verified using a Leica 800 rangefinder on a beautiful clear and windless day.

Here are the come ups: 375yds 4min, 550yds 7.5min, 650yds 9.5min, 750yds 12.0min, 950yds 17min (predicted was 16.75min). Muzzle velocity is 3150fps. 7Rem Mag with moly 162gr Amax. Rifle Savage 110 w/brake (I like to spot my impacts). Scope my trusty Elite 4200 6X24 w/ mil dot.

Just input my data G7 drag function. 0.625 BC and voila. That's the drop table that comes out. Pretty flat....

Now change to a G1 drag function and change the BC value until you get something close. I bet you laugh at what that value has to be. Try with the other 5 G functions and have some fun. You will quickly come to the same conclusions I did.

So when comparing BC's, ask which drag function was used in the calculation of that value. The number is not just the number after all.

I hope that the bullet industry will someday standardize the BC values vs G drag function (all flat base bullets use one G function, BT/VLD designs another or whatever) so that we can continue to compare apples to apples as we have been lead to believe all these years.

Jerry
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  #14  
Old 08-31-2005, 04:36 PM
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Re: What the heck is goin on?

Jerry, it's so funny that you say that now because I thought about that a long time ago and then for some reason I read something that said most bullets use the G1 drag function. So I figured that if it was standardized I just wouldn't mess with it but it could quite possibly be my culprit. Because it doesn't matter what BC I use it just NEVER comes anywhere close. I had one that was 4 minutes off at 300 yards [img]/ubbthreads/images/graemlins/confused.gif[/img]. But I will give the other G functions a try, THANKS!
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