Trench coat "gun flap"?

[Jeff M]

Was wondering, what is the actual purpose of the "gun flap" on the right shoulder on some trench coat designs?
Style only?
Sure won't provide padding for a rifle.
Help keep the rain out if you button the coat all the way up....covering that last button?

 

[Story]

Storm (Gun) Flap – Assumed by many to be padding for a rifle butt, the “gun” flap is actually a protective flap to ensure water does not slip into the jacket as it runs down the shoulders. It effectively serves as a cap, keeping the wearer dry, assuming he has on headwear.

http://artofmanliness.com/2010/10/20/man-guide-trench-coat/

 

[Jeff M]

Great link. Thanks.

 

[Doctor Damage]

Storm (Gun) Flap – Assumed by many to be padding for a rifle butt, the “gun” flap is actually a protective flap to ensure water does not slip into the jacket as it runs down the shoulders. It effectively serves as a cap, keeping the wearer dry, assuming he has on headwear.

That's exactly right: they're rain flaps. Who can say why everyone started calling them gun flaps? One of those strange quirks of the language (but I think we can blame a marketing person somewhere, somewhen who decided that "gun flap" sounded cooler than "rain flap"). On most modern coats they're just a style detail since most people wear synthetics and what-not when it's raining.