I hear ya about the new gun worries. I got an AR-10 this winter, and I just had to go break it in. The break in suggested that I clean it every shot for the first 10 shots, then again ever 10 shots up to 100. It was a pretty serious session going out in the mountains doing all that myself (GF helped a little, but mostly just watched) it wouldent have been so bad if it wasnt freezing cold.
After about half the break in, it started snowing, but I wasnt going to just pack up and quit, and then have to go through all that again, so I kept going till I was done. Luckily for me, it didnt snow more than a light dust. Had it been a serious snow, there's no way I would have stayed. I dont want a bunch of snow or rain on my nice brand new rifle, especially since it's the most expensive gun I own!
Anyway, my point is, go shoot it when your ready. It's your rifle, your friends will just have to deal with it
if they want to shoot one so bad, tell them to go buy their own, and you'll go shoot it in the rain with them.
Also, like said above, if you do, it's not gona hurt it. Just be sure to clean it when you get home, and be sure to get ALL the water out of it, even use a compressor or hair dryer if you have to, and then do a thorough cleaning and oiling, Your gun will never know it was wet!