Hold on. Just because you can do something, doesn't mean that you should.
If the guns are really from the 60's, I would not shoot steel out of them unless they are in 70-80% condition already. Browning did not make very many 20 gauge A-5s before they got into bed with the Japanese at Miroku in the mid 70s.
A perfect A5 in 20ga from the 60's is worth over $1,000 wholesale, (around $1,500 retail-at places like Cabelas) That same gun in 70-80% is worth around $400, so shoot away.
More information is needed, like serial #range, condition, choke etc. before you shoot any "old gun". Im all for using classic guns in the field, just know what you have before you beat up or misuse a collectible gun.