Please build one of these, it would be epic! The war hammer/spike is pretty cool, but the example in your photos is clearly a firearm that was built for display or very light shooting. It's definitely not something that will stand up to the hardships of combat.
Originally, hackbuts (and some handgonnes) were made were made with a spike on the tiller (primitive stock). This spike was used to hook the archaic firearm on the wall of a castle or elsewhere, and would essentially stop the firearm's recoil when it was fired (can't recoil if the gun is locked in place with the spike). That was the main purpose of the spike, but it could also come in handy during hand-to-hand combat. So, this primitive handgonne is similar to the firearm in your photos. The barrel of my handgonne could be used as the war hammer and the wall spike could be used as a combat spike.
The handgonne barrels in the photos below are original. The handgonne barrel mounted in the reproduction wood tiller is from about 1400, and the the 2 loose handgonne barrels in the last photo are from the 1370's (and were actually used in the Battle of Aljubarrota on August 14, 1385!). The 2 Aljubarrota barrels would have been mounted to a tiller the same way as the barrel from 1400.
If you're planning on making a replica of the war hammer/spike firearm, you could make one of these early handgonnes as well to show the progression of early firearms development. These are very different from the gun you posted photos of, but they are actually quite similar in the way they can be used in combat once you fire your shot. The original handgonnes in my photos below were accurate to about 25 yards, so you're extremely close to the enemy when you engage them. You'd probably only have time for 1 or 2 shots before the handgonne becomes a club/war hammer. There are people who cast replicas of famous handgonnes from the 1300's and 1400's, but I can't remember if they come with plain tillers or tillers with a wall spike.