I have an alloy barrel in which I had the barrel lug bored out to fit my stainless T/C frame. When I first purchased the barrel, I had no idea that it wouldn't fit my frame. I called Thompson and they told me to send it out to them with my frame. In a matter of 1 week, I received my frame and newly bored out barrel lug that fit perfectly at no charge. I only had to pay for the postage to get the set out to Thompson.
In essance, the hole in the lug of the alloy barrel is too small to fit the hinge pin of the modern frames and needs to be bored out in order to fit correctly. If Thompson can do this work, I don't see why they couldn't do the same to a frame. I'm not sure how many barrels you have in Armour Alloy but if you only have one or two, you might try calling Thompson and seeing if they can bore your frame and barrel lugs to fit the hinge pins of the modern frames. By doing this you will be able to use your current alloy barrels and purchase new barrels in stainless or blued steel.
I'm not a gunsmith but I am concerned about safety when shooting or doing anything for that matter. In my mind, if something is questionable in it's fit, I wouldn't trust shooting anything through it. Although you think something feels locked tight, I'm sure that the pressures released from firing various ammunitions will far exceed what you can exert on the firearm with your hands. If fit is questionable, you may be leaving yourself open to escaping gasses or the action opening up during ignition in which case you may be replacing the bridge of your nose with a hot piece of brass.
Again, maybe I'm wrong about this but I wouldn't trust it. However, you may ask the people at Thompson about it. They were very knowledgable and helpful when I called them and had services done.
I hope that helps.
