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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Shooting in the Rain?
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<blockquote data-quote="Buffalobob" data-source="post: 87155" data-attributes="member: 8"><p>I told you JB would know something. </p><p></p><p>Here are the details of a calculation that I did on another forum on the same question. Missing from the calculation is the effect of "glancing blows" from raindrops on the stability of the bullets and the lowering of BC from yaw caused by such a glancing blow. Nor did I include that fact that raindrops are a liquid and will deform on impact which will tend to lessen any effect of the collision,(if you have ever done a belly buster off a diving board you know that water is not "soft").</p><p></p><p>For those who wisely chose not to wade through the calculations here is the bottom lines.</p><p></p><p>The amount of rain from the nearest rain gauge on the last light gun match at Williamsport was only 0.32 inches over about a four hour period. It will normally rain once a month a hard rain of 1.0 inches in the eastern seaboard states. A hurricane will drop about 10 inches of rain. My calculations say you would need the amount of raindrops in the air that comes from a hurricane to affect bullet path at 100 yds. For a thousand yards you would need it to be raining about ten times as hard as it was the last match at Wiliamsport. </p><p></p><p>For the non-geeky people, a good rule of thumb is that if it is raining so hard that you cannot see the target then you will need to shoot high. /ubbthreads/images/graemlins/confused.gif</p><p></p><p>For all of you fellow geekies here is something to criticize:</p><p></p><p>mass of a raindrop is about 0.008 grams and falls at a speed of 8 m/sec. Momentum is about 0.064gm/s</p><p></p><p>150 grain bullet at slightly over 3000fps give the following momentum.</p><p></p><p>At 15 grains per gram then bullet mass is 150 divided by 15 = 10 grams</p><p></p><p>Velocity is 1000m/sec</p><p></p><p>Momentum is 10 grams times 1000m/s = 10,000g/ms</p><p></p><p>collision impact of one raindrop with one bullet is</p><p>10,000gm/s + 0.064 gm/s</p><p></p><p>You would need to hit 150 rain drops in 100 yards to get a 1% deflection. This would be one drop every 18 inches</p><p></p><p>I may have missed a conversion factor but I think this is a rainfall event of 10 inches per hour (about what you get with a hurricane). So when your bullets start striking low at 100 yds in a rain you really should be shooting from your boat and have your PFD on and next time do not ignore the evacuation order.</p><p></p><p>On the other hand if you are shooting at 1000 yds you definitely are going to be a significant amount low when you have a "good rain" not a drizzle but a nice steady rain. I question whether you could see the target at 1000yds in the amount of rain needed to cause a low strike.</p></blockquote><p></p>
[QUOTE="Buffalobob, post: 87155, member: 8"] I told you JB would know something. Here are the details of a calculation that I did on another forum on the same question. Missing from the calculation is the effect of “glancing blows” from raindrops on the stability of the bullets and the lowering of BC from yaw caused by such a glancing blow. Nor did I include that fact that raindrops are a liquid and will deform on impact which will tend to lessen any effect of the collision,(if you have ever done a belly buster off a diving board you know that water is not "soft"). For those who wisely chose not to wade through the calculations here is the bottom lines. The amount of rain from the nearest rain gauge on the last light gun match at Williamsport was only 0.32 inches over about a four hour period. It will normally rain once a month a hard rain of 1.0 inches in the eastern seaboard states. A hurricane will drop about 10 inches of rain. My calculations say you would need the amount of raindrops in the air that comes from a hurricane to affect bullet path at 100 yds. For a thousand yards you would need it to be raining about ten times as hard as it was the last match at Wiliamsport. For the non-geeky people, a good rule of thumb is that if it is raining so hard that you cannot see the target then you will need to shoot high. [img]/ubbthreads/images/graemlins/confused.gif[/img] For all of you fellow geekies here is something to criticize: mass of a raindrop is about 0.008 grams and falls at a speed of 8 m/sec. Momentum is about 0.064gm/s 150 grain bullet at slightly over 3000fps give the following momentum. At 15 grains per gram then bullet mass is 150 divided by 15 = 10 grams Velocity is 1000m/sec Momentum is 10 grams times 1000m/s = 10,000g/ms collision impact of one raindrop with one bullet is 10,000gm/s + 0.064 gm/s You would need to hit 150 rain drops in 100 yards to get a 1% deflection. This would be one drop every 18 inches I may have missed a conversion factor but I think this is a rainfall event of 10 inches per hour (about what you get with a hurricane). So when your bullets start striking low at 100 yds in a rain you really should be shooting from your boat and have your PFD on and next time do not ignore the evacuation order. On the other hand if you are shooting at 1000 yds you definitely are going to be a significant amount low when you have a "good rain" not a drizzle but a nice steady rain. I question whether you could see the target at 1000yds in the amount of rain needed to cause a low strike. [/QUOTE]
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