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

In August 2022, newly uncovered documents came to light that 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.

This source is a personnel commendation in Floyd Thomas's personnel file, commending him for his work on the 105mm project and volunteering to fire it because no one at Douglas would (or perhaps could) fire the gun. Floyd was an Ordnance Technician in the employment of the Air Services Technical Command, Western Division, at Los Angeles, CA.

The commendation letter, provided by Floyd's grandson, Eric, is dated 7 May 1945, so the tests must have been concluded before that. The commendation also comes from the Air Services Technical Command, Western Division, so that unit must have been overseeing the tests in some way.

Both Floyd Thomas and the ASTC, Western Division are based in California, so it seems likely the tests occurred there at one of the bases.

There is still no mention of the name of the project.

The citations reads:
It is desired to commend you for your voluntary participation as loader in the successful air firing tests of the 105MM Howitzer installation in an A-26B airplane, which is believed to be the largest weapon known to have been fired from an airplane. During this testing you participated in 2 flights totalling one hour and fifty minutes. Over 50 rounds of ammunition were fired at indicated airspeeds of 250 to 375 miles per hour. Charges varying from 50% to 115% were fired in all gun positions from 1 degree to 6 degrees elevation."

It is signed D.F. Stace, Brigadier General, Commanding.

Canon Type

This cannon was most likely a version of the T12 lightweight Aircraft Howitzer, confirmation pending. It was definitely not an autoloader.