Years ago when my dad was getting ready to apply for a patent on a trailer hitch, I did the mathematical analysis of bumper mounted hitches vs 5th wheel hitches. Everyone knows that a 5th wheel is better, but not always the best, but we needed to know how to analyze different configurations.
Long and short of it, you have 3 critical parameters, 1) the distance from the towing vehicle's axle(s) to the pivot point of the hitch, 2) the distance from the pivot point of the hitch to the trailer’s axles and 3) the weight distribution of both the towing vehicle and the trailer, primarily the trailer. The last parameter is very difficult to quantify in any simple terms. If you get the combination of these 3 parameters wrong, you will get oscillations of the trailer.
To understand the seriousness of the 1st parameter, think about a vehicle with a long rear end, like a big motorhome. As that vehicle starts into a turn (or weaves around in the lane) the hitch goes in the opposite direction as the vehicle. After a little bit of travel, it is pulled back into the direction the towing vehicle is going. Particularly with bad weight distribution, this can result in the trailer swaying back and forth and in extreme cases an oscillation that increases until a wreck occurs.
Shortening up the distance from the towing axle and the pivot point decreases the magnitude of the oscillation. You should note that commercially manufactured tractors have the 5th wheel mounted just in front of a single rear axle or closer to the front of a pair of tandem axles.
The length of the trailer’s tongue factors in because a longer tongue tends to lessen the effect of the oscillation. The ammo trailer, that came from the factory with a pintle hook on the back, has a short distancd from its own axle to the hook. In the case of an M105 trailer, that distance is much longer and can possibly cause an oscillation in the second trailer.
Remember, the first trailer might oscillate a minor amount, but that will be amplified in the second. I once saw a triple trailer rig going down I-25 and the second trailer was almost out of control. If you decide to try this, you need a chase vehicle to watch for sway because you can’t see your first trailer, unless you have no cover or load on your deuce, and I’m not sure that you could see the 2nd one either.
It is possible that the little bit of play between the pintle hook and the lunette can work in your favor by not transmitting a tiny amount of sway in the first trailer to the second trailer; I'm not sure.
Good luck, be safe and please do not give MV owners a bad name.