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Help with trajectory please "thing"

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Unread 03-14-2009, 10:28 AM
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Join Date: Mar 2007
Location: MN
Posts: 1,219
Re: Help with trajectory please "thing"

"You can expect about 5" of spin drift with the 208 Amax at 900 yards from a 1:10" twist barrel"

I'm suprised that it's that much! learn something new every day!
I used to re-load but now I "hand-load".
-- Well, at least I try --
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Unread 03-14-2009, 12:02 PM
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Join Date: Jan 2003
Location: The rifle range, or archery range or behind the computer in Alaska
Posts: 3,740
Re: Help with trajectory please "thing"

Originally Posted by groper View Post
only thing i can figure is that my 600yd drop is maybe 0.1 mil error???

does this sound ok?
A 0.1 mil error is normal. It is impossible to get any calculator to match EXACTLY your real world drops. This is where knowing your weapon comes in to play.

Originally Posted by groper View Post
i worked this out via trial and error using the "thing", is there a more methodical way other than subbing in random values to get a traj close to what you measure as actual???
1: I agree with Brian, verify your velocity before sweating much more. Also it helps to shoot more ranges for a more acurate picture of what is happening.

2: Verify you barometric pressure. I cannot stess this enough. it is a MUST know.

Originally Posted by groper View Post
Also as a side note, i needed 0.3mil left at 900 also, i didnt think spin drift would be that much, is it possible or somthing else???

0.3 seems a wee bit much for spin drift at that range but is close. Double check your scope level AND make sure youre not canting the rifle. Also depending on your global position you may see some coriolus effect which WILL add to your spin drift woes. The two combined can easily account for your 0.3 mil correction.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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Unread 03-14-2009, 06:12 PM
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Join Date: Mar 2006
Posts: 894
Re: Help with trajectory please "thing"

I think you would be closer to 2850fps, going by the results I get with my 300win and 200smk's.
Of course all setups are different.
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Unread 03-14-2009, 10:55 PM
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Join Date: Sep 2008
Posts: 327
Re: Help with trajectory please "thing"

thanks for the spindrift hint bryan my bbl is 1:10... i also trust your BC findings for this bullet, and so i used 0.633.

using this, i get my velocity @ 2940fps, and everything fits except the 600yd is out by 0.1mil, although this was shot on a different day compared to the 218 and 900, so i believe it to be accurate enough.

Ill shoot at 800 and 1000 next outing and i should have a pretty clear picture by then... by the way, for a stock remmy M700 SPS (only mod is a DE brake), the groups at 900 were sub MOA. I put almost every bullet (once dialed) into the V bull on a palma target from prone off a bipod and using my hand as a rear support. 1inch groups at 218yds... not bad for a stock bbl eh?

multiple people have published velocity very close to this for this recipe, i dont see it as abnormal. 77grns gets you circa 3000fps, but it wasnt as accurate in my rifle, neither was 78grns i also tried...

Last edited by groper; 03-14-2009 at 10:59 PM.
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