The first hunt I had my 450/400 on was a Spring black bear spot and stalk hunt in Montana.

I got into a rain storm like 400Nitro describes on 3 different days.

The wind and rain was so bad, my wife and I could not even see to walk.

When it let up a little we still had to walk for 3 to 4 hours in the rain all 3 times we got caught in the storms.

I wiped the rifle down and dried out the bores every night,

I ended up shooting a bear at point blank range in a snow storm.

On the way back home I stopped off at Champlin Arms and had JJ pull off the buttstock.

There were no signs of moisture or rust.

I have hads the rifle for several years, it has been rained on several times including 2 trips to Alaska, one for over 30 days in the field.

Just a few months ago I again had him pull off the buttstock.

No rust.
I have had my 450 No2 checked as well, no problems there either.

It is not something I worry about.

I bought them to hunt with.