In using shotgun actions in making double rifle conversions, when bushing the firing pin holes, following Neidner/Mann safety firing pin gasproof and blowout proof process, is it necessary to drill small vent holes, one per bush, to allow excaping gas to follow path to side of action, or will gas escape to the side, without such holes? Ellis Brown, in his book, converting shotgun actions to double rifles, he goes into detail about such bushings, but makes no mention at all of using vent holes. I have seen old double rifles with such vent holes, but don't see them on more modern doubles---why? By the way, a very old law in Germany, requires German gunmakers to install firing pin bushings on all guns with rifled barrels. Look what happened to one of early rifles built by Ellis Brown, with pierced primers during proof, in his book, and you will be (should be) convinced of the wisdom of bushing firing pin holes properly. Not only can it destroy your stock, but it can also ruin your whole afternoon! If you think vent holes are necessary, what diameter would you think appropriate?