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Can someone please check my math for me.

 
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  #1  
Old 03-22-2008, 12:46 PM
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Join Date: Mar 2008
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Can someone please check my math for me.

Hello, this is my first post here. Though I have been reading old threads here for awhile, and have learned allot in the process.

Anyway I am getting into this long range shooting a bit, mostly with varmints. For the time being I am only shooting a .223, mostly I am just trying to learn the ropes with something affordable to shoot.

Anyway the scope I am using is a Burris variable 14x with the ballisticplex reticle. For most of what I use it for (inside of 300 yds) I just use the different dots for my hold over, which works fine for the most part. I would like to be able to practice out to 500 hundred though with this rifle. At that range the dots are aways apart and estimating a smidgen high or low gets hard to do.

But what my theory is though is that I can still use the dots at any range, but then to also turn the knobs so I can place the cross hair right on without any guessing.

Let me run an example, and if someone could double check me I would appreciate it.

Lets say I am shooting at 450 yards.
The drop for the fourth dot on this scope is 29" @ 400yds.
My drop chart tells me I need to have 8.85 moa of elevation.
Converting 29" to moa gives me 29/(400/100) = 7.25 moa
So then I would need to dial my scope up 8.85-7.25 = 1.6 moa.
Burris uses 1/4" clicks @100 yds so to get clicks 1.6/(1.047/4) = 6.111 clicks.

Or 6 clicks of elevation using the forth dot on the scope. Does this all sound like a sound theory or am I doing something wrong. I plan on getting out and trying this theory out this weekend. Though I have not tested this drop chart yet, and I try not to change more then one variable at a time here.

This post got longer then I expected, but I appreciate any insight.

Thanks,
Will
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  #2  
Old 03-22-2008, 01:33 PM
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You state that your scope is a Burris and that they adjust in 1/4" and then you converted to MOA, if your scope adjusts in inches then their is no need to convert to MOA
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  #3  
Old 03-22-2008, 01:45 PM
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Everything is in inches but. But I don't think I can just add so many inches to whatever dot to get a father range can I. So many inches drop at 400 is going to be different at 450 right? That was my logic for doing it this way.

Will
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Old 03-22-2008, 01:55 PM
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It is inches per hundred yards (IPHY) raise the impact 2" at 100 yards and this will raise the impact 8" at 400 yards and 9" inches at 450 yards...
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Old 03-22-2008, 02:53 PM
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Quote:
Originally Posted by crusier_32 View Post
Lets say I am shooting at 450 yards.
The drop for the fourth dot on this scope is 29" @ 400yds.
My drop chart tells me I need to have 8.85 moa of elevation. First of all, don't use drop charts in moa but make them in inches, as jpw475 said, your scope uses IPHY. Instead of 8.85 moa let's use 8.85 x 1.047 = 9.27" the adjustment you need at 100 yards to be on at 450 yards. Just like using moa but we're not.

Converting 29" to moa gives me 29/(400/100) = 7.25 moa
So then I would need to dial my scope up 8.85-7.25 = 1.6 moa.
Burris uses 1/4" clicks @100 yds so to get clicks 1.6/(1.047/4) = 6.111 clicks.
Now, the fouth dot at 100 yards gives you: 29/4=7.25" not moa, inches.
So, you already have 7.25" inches and you need 9.27" inches; therefore, 9.27" -7.25" = 2.02". Again we think of what jpw475 said.
At this point 2" need 8 clicks. Move the turret 8 clicks up, and using the fourth dot you should be dead on! Do not work with moas.
Or 6 clicks of elevation using the forth dot on the scope. Does this all sound like a sound theory or am I doing something wrong. Very sound theory, if we can keep all things in the right place I think is very awesome technique. Combination of turrets and hold over. Nice. I plan on getting out and trying this theory out this weekend. Though I have not tested this drop chart yet, and I try not to change more then one variable at a time here.
This post got longer then I expected, but I appreciate any insight.


Thanks,

Will
Test it at all ranges you plan to shoot. Good luck!
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Last edited by Eaglet; 03-22-2008 at 02:56 PM.
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  #6  
Old 03-22-2008, 03:32 PM
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Crusier_32,


This is the reticle for my scope, the values are right if the scope zoom is set at 22x. If let's say I need to make a shot at 1050 yards and my drop chart or my PDA says I need 22.2 moa; then I use the bottom hash mark which is already giving me 20 moa and would dial 2.2 moa which would be 9 clicks to be dead on. You could do exactly the same with your scope. The trick is in doing lots of testing to ensure everything is in place.
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-----------------------------

-----------------------------
HEBREWS 13:8
Jesus Christ the same yesterday, and to day, and for ever.

Our Lord Jesus said that as it was in the days of Noah and
also as it was in the days of Lot so it shall be in the days...
It's happening again!!! God sent to us His prophet, and His Word
to this generation and we once more are rejecting it as was prophesied!!!

---> As promised, God Sent His Prophet to us!
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  #7  
Old 03-22-2008, 03:48 PM
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Join Date: Jun 2005
Location: Yakima, Washington
Posts: 3,833
Eaglet:

You're gonna love that new scope but one thing you might find when shooting in the field and using the extreme lower hash marks, especially at 22x, is that, although it works and you can do it, it really can make it hard to spot your own shots because the hash mark you're using is in the lower portion of your field of view.

I'd done it over the years and it works, but I've also found that, at least for me, I prefer to dial for the first shot and use the hash marks to spot my shot if I'm by myself. Usually at long range the time involved in dialing won't be a problem.

Try it and see what you think but at least for my old eyes I prefer to have as much field of view as possible.;);)

After you get it mounted and get some time in the field, let me know what you think.
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