22lr in rain

[tangolima]

It was raining pretty hard yesterday on our outdoor range. I noticed subsonic ammo doing worse than usual, while high speed rounds are more or less the same.

Is it possible that the slower bullet got deflected when it hit the rain drops?

-TL

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[Scorch]

High velocity bullets create a shockwave cushion of compressed air around then as they fly through the air. The explanation I've heard id that raindrops can't break through that compressed air. Standard velocity of subsonics don't create a shockwave, so no protection.

[tangolima]

Interesting. I thought high speed bullet just has more momentum to keep direction. The cushion theory makes sense.

-TL

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[jmr40]

I've heard that theory in relation to faster centerfire bullets. I've not seen anything in relation to bullets at 22 speeds. But that is certainly plausible and would be my 1st guess as well. But that is only a semi-educated guess.

[Rimfire5]

I haven't noticed any problems with rain. But a really heavy rain fall might have caused some problem.

Was the temperature under 45 degrees?
I have found that .22LRs are very temperature sensitive.
I think the rim primer and small powder loads team up to cause drops when the temperature is lower than 45 degrees.
I have found that, even with good match ammo, I get about 1 drop per five rounds.
At 30 degrees it is more like 2 per five.

I just don't expect tight groups when the temperature is lower than 45 degrees.

[mikejonestkd]

My experience with rimfire ammo in the cold mirrors rimfire5's post.
My summer zero and winter zero at 100 yards can be significantly different, and I regularly get one or two low fliers every group when they temp gets really cold.
I haven't really noticed significant differences between dry days and light rain as far as group sizes, and most of any differences can easily be attributed to factors other than rain.

[stagpanther]

The flip side is that air density--hence drag--will be less in superhumid air. I guess what you're asking is it possible the impact of drops as the bullet "plows" through the air enough to induce instability. The best 22lr ammos are subsonic anyway.

[tangolima]

The temperature was around 60F. Probably not the cause for inconsistent ignition. Subsonic is indeed the best for <75yd. Going beyond supersonic seems better. I'm aware of the trans-sonic effects. But its adverse effects are probably offset by shorter flight time, I think.

Not that we will need to shoot in rain often. It is just an interesting observation.

-TL

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[FrankenMauser]

We've had a few discussions about the effect of rain drops on supersonic bullets, over the 15+ years that I've been around here. I did some math in one of them.

Some disagreed with some of my assumptions, but I believe we all figured it was roughly the correct ballpark.

My conclusion (assuming constant velocity):
A .308" diameter bullet traveling at 2,100 fps to a 100 yard target has just a 0.0139% (1:7175) chance of hitting a rain drop.
The smaller the bullet, the better the odds. [of no impact]
The faster the bullet, the better the odds. [of no impact]
A .224" bullet traveling at 3,900 fps has only a 0.0054% (1:18,323) chance of hitting a rain drop in a two-inches-per-hour rain storm.

From a claimed meteorologist:

(...) the impact of a 1gr drop of water on a 165gr bullet will be negligible (something in the range of 1/10,000th of one MOA if my division serves me right) (...)

Your odds of measurable bullet deflection due to rain is roughly the same as the odds your bullet will be struck by lightning in midair.

But in the subsonic realm, the "negligible impact on the bullet," probably goes out the window. So that sounds like the answer, right?
The thing is, you have to hit a rain drop for it to matter, and those are long odds.

.

[stagpanther]

Going beyond supersonic seems better.

I've yet to see solid statistical proof of that in 22lr.--I would be happy if there were, but I just don't think it's happened with real consistency. I would be very happy to be proven wrong. Shooting at 225 to 250 yds I've never had any supersonic 22lr ammo group better than the best of the sub-sonics. The only possible exception to that is if the supersonic might reduce winddrift by a small amount--but even in that case it would likely be a very small window of wind like between 2 to 3 mph where I would imagine that would be the case.