Bullet trajectory

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Bullet trajectory

Postby tshildreth » Fri Nov 02, 2012 10:24 pm

So, I am helping my 5th grade son with his science fair project and he wants to test this question: "How does change in trajectory angle effect bullet/target accuracy?" We have the ability to set this up at our local gun club, but I am at a lose as to the best procedure/methods to use in order to produce "science fair" worthy data. Any direction on this subject would be greatly appreciated. His question is due on Nov. 15th and all his research by the end of the month.
Thanks,
s
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Project Question: How does the change in trajectory affect the accuracy of a bullet?
Project Due Date: November 15th, 2012
Project Status: I am just starting

Re: Bullet trajectory

Postby rmarz » Sat Nov 03, 2012 9:07 pm

tshildreth - Trajectory is the path of flight that a projectile takes. The trajectory is acted on by several variables. As the bullet leaves the barrel it is likely still accelerating as a result of built up gas pressure in the barrel. After leaving the barrel, it is immediately acted on by gravity and starts to drop (and this rate of drop accelerates) at a very specific rate. As it follows the trajectory, air friction will cause it to slow. As it slows, and as the force of gravity causes the drop to accelerate, the trajectory curve becomes much more dramatic. I'm not sure what you mean by trajectory angle and it's effect on accuracy. None of these dynamics really have anything to do with accuracy. There is a lot of material available on the internet that will explain all of this and more. Here is a very short explanation of simple bullet ballistics that can be a starting point. I think you have to define what you mean by accuracy before trying to apply predictable ballistic/trajectory elements to your experiment.

http://www.centerfirecentral.com/articles/traj.htm

Rick Marz
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Re: Bullet trajectory

Postby tshildreth » Sun Nov 04, 2012 10:04 pm

Ok. I agree there are too many variables on trajectory. How about this one... Does bullet quality effect accuracy? Same gun, same shooting situation and distance with the only difference being the quality/cost of the bullet. Or is that hard to quantify? Would it be better to change bullet length (22 short vs. 22 long) and test how that effects accuracy?
Thank you so much for helping us narrow this down.
tshildreth
 
Posts: 3
Joined: Fri Nov 02, 2012 10:10 pm
Occupation: teacher/parent of 5th grader
Project Question: How does the change in trajectory affect the accuracy of a bullet?
Project Due Date: November 15th, 2012
Project Status: I am just starting

Re: Bullet trajectory

Postby rmarz » Mon Nov 05, 2012 1:19 am

tshildreth - I think you are now getting closer to reducing the variables to make a more valid experiment. Most bullet manufacturers offer premium products as 'match grade' bullets that are manufactured and tested to much higher standards than their regular product offerings. In the same gun, same conditions, different ammunition will have different grouping sizes that show ranges of repeatability. I think a .22 rimfire cartridge is a good selection to do a series of tests of different manufacturers products to determining bullet dispersion (think of it as accuracy and repeatability) because it is the lowest cost cartridge and available from many sources. Some products may even advertise products as 'super accurate' or such. A test at an indoor range will minimize wind issues, and a gun vise or ample supply of sandbags will reduce aiming variables. This interest could lead to a lifetime hobby of target shooting involving hand-loading of ammunition. I have hand loaded target ammunition for many years and for several of my favorite rifles keep detailed logs of bullet selection, powder types and loads, primer choice, insertion die setups, etc to lead to the most accurate combination for target purposes. I am often able to attain less than 0.5" groupings (5 bullets in essentially the same hole) at 100 yards after many combinations of experiments. Here is a link to one manufacturers description of 'match grade' bullets. If you read an evaluation of a rifle in a shooting magazine, the articles all evaluate the accuracy of 3 or 4 different types of ammunition in the gun so you can see the effect of bullet choice on accuracy.

http://www.extremeaccuracy.net/bullet-info/

Rick Marz
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Re: Bullet trajectory

Postby tshildreth » Sat Nov 10, 2012 4:52 pm

Excellent! Thanks so much for your help. We are very excited to go forward with this project. We'll keep ya posted.
tshildreth
 
Posts: 3
Joined: Fri Nov 02, 2012 10:10 pm
Occupation: teacher/parent of 5th grader
Project Question: How does the change in trajectory affect the accuracy of a bullet?
Project Due Date: November 15th, 2012
Project Status: I am just starting


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