105mm Canon

There is evidence to suggest that at least 1 Invader was equipped with a prototype 105MM cannon in the nose.

First Source

There is a single drawing showing this gun in a similar fixed position in the nose as the 75MM version.

The source record states that it was the largest forward firing cannon ever flown, but gives no indication if it was actually fired.

When I first came across this account it was just the photo by itself posted in a forum thread. A lot of "experts" on the thread were quick to call it fake stating that the artist who drew it doesnt understand the inside of planes, or saying there's no record of it and dismissing it. The drawing shows the cannon mounted in a very similar manner to the 75mm cannon.

I did some searching and uncovered the source of this photo, a single book which features this photo as a footnote of sorts while discussing aerial cannons.

Normally, I wouldn't put too much stock into a single report, but this report comes from "The Machine Gun, Volume 5". This book was written by Col. George M. Chinn, USMC (Ret). For those who don't know, Col. Chinn was the United States' foremost weapons expert during and after WWII. He has been called the "Bill Gates of Machine Guns" and this work was the culmination of his life's work. Given that it was he who reported this gun, I am inclined to believe him, since he is a bonefied expert on weaponry.

Unfortunately, Col. Chinn's book didnt give any indication about when or where the 105mm tests took place, who was involved, or what the project name was. For a long time it was a dead end.

Second Source

Newly uncovered documents show that this weapon was indeed fired at least 50 times using a variety of different ammo loadouts spread out across two different flights. The tests were conducted in California, and Floyd A. Thomas was the gunner who volunteered to fire the cannon during the tests. The tests were concluded by Jul 1945.

I have been able to narrow down that this type of cannon was most likely one of two types, either the T12 Aircraft Howitzer or the T9E2 Autoloading Recoilless Howitzer, both of which appear to have been manufactured by Oldsmobile.