I'm no expert on historical firearms, but I'll wager a guess from what I can see in the photo. Hopefully someone else will be able to verify or clarify more specifically.
Looks to me like it might be a Browning M1918 from what you can see in the picture. You can see the charging handle on the top of the receiver at the rear which means it isn't a 1919 variant since they had charging handles on the right side of the receiver attached to the bolt. The 1917 was a water-cooled gun that looks a lot like the one in the photo, but because it was water cooled it had a huge shroud around the barrel to facilitate cooling. Then in 1918 they released a lighter air-cooled version of the 1917 called the M1918 that was intended for aircraft usage. Because of this it ditched the water jacket and opted for a heavier barrel and shroud which it appears might be the case in this photo.
So that's my guess from what I can see, hopefully it at least helps you start in the right direction as far as identification.