Anyone out there a dedicated enough shooter to have range time logged (read waterlogged) in the rain?? It occurred to me that, while I am a stubborn enough hunter to hunt in the rain, I never have checked at the range to see how much additional bullet drop I am getting in light, normal and heavy rain.

I have some time this morning, so I could muse a bit..
here is what I got to say, mind you I might be wrong..

====================================================
==== case 1 ===========================================
==== assuming the rain does hit the bullet ========================
====================================================

Here some assumption are taken :
- the projectile is a cylinder with straight wall from meplat to heel
- the bullet flight duration is 1 second

Rainfall is measured by a gauge which have a funnel to catch rain and a measuring cup under the funnel.
The measuring cup surface area is usually exactly 1/10 of the funnel catchment area,
and the measuring standard should be height of catched rain / hour.

Statistically anything below 2.5mm (0.1 inch) of rain is classified as light rain,
2.5 - 7.5mm (0.1 - 0.3 inc is moderate rain
and higher than 7.5mm (0.3 inch) is heavy rain.

Ok, having established the rainfall measurement, lets forward to the next step.
2.5mm / hour rain is 2.5mm / 3600 seconds or 0.000694mm / second .

A very heavy rainfall of say 15mm/ hour, the rainfall is 0.00416 mm/ second.

Ok, now lets get a large and heavy .308 woodleigh of 200 grains length for our study case
The projectile length is about 25mm (1 inch) (I dont have one handy to measure, so I used what I have in memory - 25mm)
It is a good projectile to use for this study because it have a meplat area of about 0.270,
Or we could even say it is roughly a cylinder from meplat to heel.

So, we have a surface area of 7.62 x 25 mm = a bit less than 200 sqr mm projected from its side.
so if we take the standard rain gauge, the measuring cup should be 20 sqr mm cross section.

Ok, now the actual rain that will be catched by the projectile in 1 second would be 20 x 0.00416 = 0.0832 mm cube
with the weight of water at 1g / 1 mm cube, the weight of water that may hit the bullet in 1 second is 0.0832 gram
now with 1 gram is approx 15.4 grain, so 0.0832 x 15.4 = 1.28 grain

So by all the above lengthly calculation, I can deduce that the actual rain that may
hit the bullet in 1 second is 1.28 grain.
At my projectile weight of 200 grains, that represent 0.64% of the total weight.

I believe the tolerance of factory made projectile is about that..
so here I proof that there is NO difference in trajectory due to rainfall

====================================================
==== case 2 ===========================================
==== assuming the rain does NOT hit the bullet =====================
====================================================

Due to the high rpm of inflight rotation of the projectile, it would be covered by a laminar layer of air.
Thus will deflect any rainfall that may came close to the projectile.

Thus no difference in trajectory may occur.

====================================================
==== case 3 ===========================================
==== Gelan need some beer ================================
====================================================

This morning I donated 2 cases of my thoughts to you, now please donate at least a case of beer to the cause.



Seriously, you may get more effect from the wind that almost always accompany rains than the actual rain itself..

So here I rest my case

I actually read a ballistic article once that talked about this very thing. Their stance mirrored gelandagan's. They wrote the only thing rain would effect would be if water was in the muzzle of the rifle. They called that a "rain shot" and the round could go anywhere but to the target.

I've also read rain has no affect on in-flight trajectory from sniper material. gelandangan, some great calculation! I think you were a bit optimistic. If a rain drop and bullet did co-exists in the same physical space, the speed of the bullet would limit any contact to the frontal area. The rain drop would be realatively motionless.

slimjim wrote:

I think you were a bit optimistic.

Thanks Slim, I think the word you want to use is simplistic.

Yeah, I am calculating the fact that the rain water is moving perpendically to the direction of projectile movement.

OTOH, we can make it into

============================================
====== CASE 4, ================================
====== if the raindrop is HIT by the bullet. ===============
============================================

Now this would have increasing complexity on the calculation because it has to do with the fluidity of the raindrop.
Acidic rain would tends to have lower surface tension thus would affect the flight path less than say, Alkaline rain.
The amount and type of solid polutant captured within the drop of rain would create different result..


I would defer this calculation to someone else with more lucid braincell than mine.

Actually it should be if the bullet COULD hit the rain drop.
Remember that the bullet is travelling at supersonic speeds and the shock wave in front of the bullet would easily deflect the rain drop - turning it to vapor before the bullet could contact it.
Try shooting a slik scarf with that bullet and you will see what I am saying.

Like (I'm sure) PaulS. I've hunted in the Nortwest (Washington and Oregon). It is somewhat rare to have a day during hunting season that it does not rain. I have had no problem dropping a deer in a heavy rain at distances that you can see a deer in that heavy rain.

But what if it's raining cats and dogs???

Great comments, guys. I have shot deer in the pouring rain, but so far only at 100 yards or less. I never tried any long range rain shooting.

Another factor is that bullets for most cartridges are supersonic for at least a good portion of their flight. The shock wave ahead of the projectile should deflect raindrops.

Thanks for the confirmation of my gut-feeling that rain will have little or no affect on bullet trajectory.

Gelan - Guess I owe you a case of beer, mate.

rain = zero effect .

wind/gravity are the affecting factors.

Hey look!! Ol' Stovey stopped eating long enough to talk to us...

Hi guy..

Hi Bushy! *chomp-chomp-buuuurp* scuseme.

I knew it wouldn't last. Just too good to be true, I guess.

Oh well...Back to the original subject.

Raincoats for bullets forced to fly in the rain...

44marty wrote:

But what if it's raining cats and dogs??? Gelan - Guess I owe you a case of beer, mate.

Marty...if its rainin' cat and dogs mate, well then we will have to do more calculations cause thems varmints and would need a different calibre than Gelan's .308 BLOOMPPH.

Well done Gelan...a carton of ale well earned mate.

I with you Bushy...in all my years of shooting, as a target shooter, hunter and soldier, I have never found rain to have any more effect than annoying the shooter. In the Army I qualified in shooting, to the same standard, on a number of occasions in the rain. The only detrimental effect I have seen rain cause is to keep game undercover making the buggers harder to find.

Cheers, Vince

The biggest issuethat has to be dealt with while shooting in the rain is cleaning the rifle when your done so it doesn't rust.

Huh? Does it rain in Texas?