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Come on out - It's safe now

 
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  #22  
Old 08-05-2005, 11:36 PM
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Re: Come on out - It\'s safe now

LWolken,

When you have bullets of relatively equal bullet weight to compare that is a good idea at least for the individual to test bullets head to head.

In the case of the heavy wildcat Bullets, there is nothing out there that will match up of equal or similiar weights. Example:

156 gr ULD RBBT .257"
169.5 gr ULD RBBT .277"
200 gr ULD RBBT .284"
350 gr ULD RBBT .338"

Still you can take two different bullet weights, zero them at the same range, say 500 yards and measure mid range tajectory and say an 800 yard drop and be able to figure out which bullet is most ballistically efficent.

We have actually been doing this all along as well but again some feel this offers nothing of value in comapring one bullet to another.

Personally, I think you only have to test for yourself and whatever system you use that allows you to develope accurate predictable drop charts is the system you should use.

Good SHooting!!

Kirby Allen(50)
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  #23  
Old 08-06-2005, 08:35 AM
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Re: Come on out - It\'s safe now

[ QUOTE ]
What qaulifying information are we after and what can be a consensus on how to go about getting B.C. figures that all can understand and agree upon?

Are we talking about having 2 chronographs?

Are there any programs out there that can convert to sea level from the conditions of where we(tester) are at at the time of testing?

[/ QUOTE ]

The information needed depends on what is missing.
If the observation is drop or clicks/MOA of compensation, then example qualifiers would be scope height(exact), MV, Atmos data, Scope type("/100yds, 1/8moa, etc), base angle, zero, shot angle, wind compensation, bearing, lattitude.

Many of these are eliminated with 2 chronographs. So this would be the preferred/more accurate method provided you aren't introducing even more error. Cheap chronos, narrow screen spacing, #of shots in avg, etc, would need to be taken into account if all is based on this data alone.

Then with software, trial & error to get a local match and again from hypothetical SL Std BCs. This would need to be derived and validated with more than one program because they all have strength and weakness in different areas.

This is why some of the best bullet makers don't advertise BC. They don't know, and don't have the resources or motivation to find out. Their bullets sell based on other attributes.
Some tolerances and assumptions would always have to be accepted. But there are plenty of resources here to pinpoint and convert observations into truly usable information -across the board. Just takes patience, and a culture which allows for open -polite- questions.

But why is this important to do? Like Fifty suggests, all that matters to you is what you need to enter in your software, right? If you hunt locally only, and have a particular caliber/cartridge/twist already, then it probably doesn't matter for you. Buy it, try it.
But for those who hunt abroad, or those considering a new rifle chambering and shooting system, it all starts with a bullet. And comparisons in choice can only occur within the same standards.
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  #24  
Old 08-06-2005, 12:54 PM
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Re: Come on out - It\'s safe now

Maybe I should post the raw data from the test I did recently so people can see how I went about it. Not as an example of "the only way" or "the best way" but just the way I did it with the equipment I had.
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  #25  
Old 08-06-2005, 02:06 PM
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Re: Come on out - It\'s safe now

If one was to take a 4x8 piece of plywood(i believe like kirby does) and start at 100yards and get your zero(aiming point would be the top of the plywood) and move the plywood to 200 still maitaining aiming point of the top of the plywood and fire a group and then circling or marking the group and then move it to 300 and so on while still maintaining aiming point of the top of the plywood.
NOTE--- One would not adjust the elevation turret---

One will be able to get drop in inches out to 500-600 yards. Can one then go back to the ballistic programs and match up the drop figures while recording all the necessary data like temp, humidity, baro, bearing, lattitude, MV, scope height, base angle???
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  #26  
Old 08-06-2005, 02:34 PM
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Re: Come on out - It\'s safe now

[ QUOTE ]
If one was to take a 4x8 piece of plywood(i believe like kirby does) and start at 100yards and get your zero(aiming point would be the top of the plywood) and move the plywood to 200 still maitaining aiming point of the top of the plywood and fire a group and then circling or marking the group and then move it to 300 and so on while still maintaining aiming point of the top of the plywood.
NOTE--- One would not adjust the elevation turret---


[/ QUOTE ]

Matt27, that's exactly what I did last fall. Took all most all day. Using a tape measure marked out to 500 yds in 100yd increments. Used cardboard box of sufficient height (I hoped based on factory bc). Was across a dry lake bed.

Let me tell ya, that was a lot of walking, the lake was dry, but when you broke through the crust you could sink up to your knee. Thus no driving.

Time of day was a factor as too much time was taken. After I was done I made some SWAGs (scientific as I was holding a calculator in my hand when I made 'em but mostly WAGs).

After much more shooting an playing I came up with a drop chart. After all that work, my first shot # 650 was spot on.

Why, not this. Set up a regular paper target target at say 100 or 200 yds. Align it so that the 4X8 large target is lined up properly at say 500 yds. Line up the near target exactly at the top edge of the far target (if that can be done) then shoot.

Will the "paper" mess up the bullet profile?
If I'm successful w/getting accurate drop measurements using this method and develop a usuable drop chart out to 800 yds does it make any difference what the velocity or bc is? (Just thinking very basically)

Am shooting .338 252gr bullet w/o published bc. They're so purdy I kinda hate to shoot 'em. Have 'em all lined up on the shelf in the shop in itty bitty grass skirts so they wiggle when I close the door hard. [img]/ubbthreads/images/graemlins/wink.gif[/img]
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  #27  
Old 08-06-2005, 06:59 PM
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Re: Come on out - It\'s safe now

[ QUOTE ]
Can one then go back to the ballistic programs and match up the drop figures while recording all the necessary data like temp, humidity, baro, bearing, lattitude, MV, scope height, base angle???

[/ QUOTE ]

Yes, with as much of that info as you can get loaded into your ballistic program, you can trial & error BC input till drop(not path) matches. A real good program will allow a drag curve such as G7 to be used for this. With high BC bullets that would be more accurate. But for hunting bullets at reasonable distances, G1 works well enough.
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  #28  
Old 08-09-2005, 01:33 AM
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Re: Come on out - It\'s safe now

[ QUOTE ]
<font color="purple"> Maybe I should post the raw data from the test I did recently so people can see how I went about it. Not as an example of "the only way" or "the best way" but just the way I did it with the equipment I had. </font>

[/ QUOTE ]

Using two accurate/repeatable chronys and calibrating them as you mentioned earlier is the best way short of radar. It wouldn't be hard for me to show the error bounds of the other approaches are an order of magnitude greater.

I'm not condeming the drop data approach - but if you want to know the BC with an error bound (%) in the low single digits - use dopplar radar or two chronys.
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