+1 to Larry's comments.
Sounds like you used steel rings that didn't exactly fit the aluminum bases, or were loose. Mainly because none of your barrels need anything special, they are not handcannon class cartridges. They don't need larger base mounting screws, or 6 screw bases. But what you use to mount your scopes on them does need to be designed to work together properly, fit each other properly, and be installed correctly. Aluminum bases are fine for these barrels.
That said they are best used with aluminum rings as well IMO. Something I learned over 40 years ago from JD Jones who makes true handcannon barrels for Contenders (and Encores), and aluminum bases/rings for them. They worked just fine on my meanest Contenders from him and a couple of other custom barrel makers. And they did take a lot of the strain off the scopes.
But I used steel bases and rings far more often on them and my Encores, some with 6 screw steel bases and up to 4 steel rings on the real cannons. Also meant the scopes used had to be only those few that could take the full recoil though as the steel bases/rings transfered it to the scopes more than aluminum sets do.
L.