[Rich Z]

We've been getting a lot of rain here in north Florida lately, and that got me thinking. Anyone do much shooting in the rain at all? I know I don't simply because I just don't want my guns getting wet.

But the reason I am asking is I was wondering if the projectile fired through heavy rain would create a visible trail in the rain. I guess it it were raining too heavily, you couldn't see it anyway, but in a moderate rain, can you actually see a trail through the raindrops?

What about accuracy in a situation like that? Do you get substantial deflection of the projectile by impacting the rain drops?

I've fired some pretty hot loads using some .223 52 grain SX projectiles that left a grayish looking trail behind them as they headed out to the target. Weird looking. I had holes in the paper, so the bullet didn't disintegrate on the way to the target. But I think those thin skinned projectiles might have been deteriorating slightly for a trail like that to be visible.

Anyway, just thinking out loud.

 

[GBullet]

If you use a scope with a fairly high magnification you can watch the bullet. For example, with a 20x scope atop a heavy .22LR rifle, you can see the bullet as a small gray blur against a white or manilla target. When the sun glints off of the bullet, it's easier to see it.

Rain does degrade accuracy. How much it degrades it is a function of the bullet's mass, velocity and stability. Rain causes the bullet to deflect slightly, but the gyroscopic effects amplify it. Shooting an accurate .22LR in a heavy downpour at a target 100 or more yards away can double the group size.

All bullets travel in a tiny spiral about their trajectory, the product of something called nutation. Imagine stretching a screen door spring too far, so it stays stretched. Now take that stretched spring and bend it to resemble the arc of the bullet's flight. The result looks like the true path that the bullet follows.

Suppose that you are shooting at a target 100 yards away and a rain drop hits each bullet in exactly the same manner when it is 30 yards away. The group will be simply shifted from its normal point of impact. However, if one bullet hits a rain drop at 20 yards, another at 40 yards, and the rest at 65 yards; the spiral pattern is irregularly shifted. The resulting group will almost certainly be larger as well as shifted.

Let me also add that under the right conditions, the bullet can leave a trace in the air immediately after it pass through it. This is due to the swirling of the air behind the bullet.

 

[Rich Z]

Hmm, this went off on a tangent rather interesting.

How pronounced is this spiraling effect the bullet path takes? Is there any rule of thumb for a radius to expect for any given caliber and/or velocity? Are we talking about fractions of an inch, or inches in radius?

If it is pronounced enough, how the heck can you predict precise bullet placement except at exactly one exact distance? What are the chances that targets 100, 200, and 300 yards will have the bullet impact them at exactly the same arc in the spiral? So it's possible a properly sighted in rifle at 200 yards could impact the target at the 8 o'clock position at 100 yards and the 3 o'clock position at 300 yards (or visa versa)?

I think I read somewhere that the .50BMG doesn't even become stabilized in flight until after 200 yards or more (maybe more, I can't remember), so accuracy can suffer simply because the bullet hasn't stabilized if shooting at close targets. Now is this spriraling effect part of the pre-stabilized flight or is this something that exists from muzzle to target, no matter how far away?

 

[GBullet]

Hmm, this went off on a tangent rather interesting.

How pronounced is this spiraling effect the bullet path takes? Is there any rule of thumb for a radius to expect for any given caliber and/or velocity? Are we talking about fractions of an inch, or inches in radius?

Usually less than 1/4 to 1/2 inch at most shooting distances. You can calculate the radius of the spiral for a given caliber, but it takes some math.

If it is pronounced enough, how the heck can you predict precise bullet placement except at exactly one exact distance? What are the chances that targets 100, 200, and 300 yards will have the bullet impact them at exactly the same arc in the spiral?

It's not very likely, but this effect is small.

So it's possible a properly sighted in rifle at 200 yards could impact the target at the 8 o'clock position at 100 yards and the 3 o'clock position at 300 yards (or visa versa)?

Yes, although the spiral is generally less noticable than wind and shooter error.

I think I read somewhere that the .50BMG doesn't even become stabilized in flight until after 200 yards or more (maybe more, I can't remember), so accuracy can suffer simply because the bullet hasn't stabilized if shooting at close targets. Now is this spriraling effect part of the pre-stabilized flight or is this something that exists from muzzle to target, no matter how far away?

In these cases, the bullet is stable, but it does exhibit considerable yaw. It's like a child's top. When you first spin the top, it may wobble but it soon settles down. The top is stable in that it does not fall over or skitter off of the table, but may wobble in one spot for a second.

 

[41mag]

G BULLET, your comment about the trail got me to thinking.What you describe sounds alot like a jet contrail.A low pressure area directly behind the bullet that disturbs the airflow.Just noticeable because of the rain.That might account for Rich's "gray trail".
Also,when shooting handgun silhouette you can,sometimes,follow the bullets bath through a spotting scope.I would think that a big,heavy,slow handgun bullet might make a more noticeable path through the rain.
Rich,I'd bet that your 50 makes an even better display.I would venture that the velocity is too high to really follow with the naked eye though.
Interesting thread.

 

[Rich Z]

Well, I doubt there are very many instances when you fire a .50 that you DON'T blink when you pull the trigger. By the time the eyelid has reopened, the bullet has hit the target. I don't tend to blink shooing a .223, but the .50 is a whole 'nother animal. Probably the eyeball detecting that scope rushing towards it triggers an involuntary response that would take some training to overcome. Plus the muzzle brake makes a lot of turbulence, both in noise and air movement, that every part of your body can detect this. Actually shooting a .50 is a good way to open up blocked sinuses.

 

[GBullet]

G BULLET, your comment about the trail got me to thinking.What you describe sounds alot like a jet contrail.A low pressure area directly behind the bullet that disturbs the airflow.Just noticeable because of the rain.That might account for Rich's "gray trail". ...

41mag, I almost used the jet contrail example myself.

I think that 41mag is right about Rich's "gray trail". For ease of discussion, let's pretend that the air is flowing around the bullet, rather than the bullet moving through the air.

As the air moves around the bullet, the air close to the bullet slows greatly. When the air reaches the bullet's base, the flow separates causing a vacuum and considerable swirling, or turbulence. The vacuum may be strong enough to cause moisture in the air to condense as a trail. Even without this effect, the turbulent air will act like mirage and thus form a trail, too.

 

[andy]

It's easy to see fresh cast .45 lead bullets

in flight, especially if the sun is behind the shooters and spectators, in the early evening. The fresh lead is silvery in color, and at 800 fps, its basically lumbering along. Plated .22lr's, from a 4" barrel at about 900 fps, can be fleetingly spotted, under similar circumstances, by the shooter who is looking over the slide and firing really swift repeat shots.

 

[Garand]

When your a competitive shooter, you take your chances on the weather. About 3 weekends ago I shot a 2 day 3 gun match, all the shooting was between 5-100 yds and it pissed down rain for almost 2 days straight. Sh*t happens. While not pleasant, I was still out shooting.