...from Fr Z, here's a copy and paste job:
From a reader:
Can a beretta be used in the OF? When would it be used?
Yes, without question! But make sure that it is clean and in good working order so that it doesn’t misfire.
I would use the beretta primarily when there are too many extraordinary ministers charging the altar. Another possible moment would be when the choir sings On Eagles Wings or another ditty of that sort.
The best way to use the beretta is to rise… first removing your biretta – which is perfectly correct to use in celebrations of the Ordinary Form of the Roman Rite – and, taking aim, go for head shots.
I have learned through hard won and tough experience that you should immediately reload!
To save you and everyone else that embarrassing hitching up of the alb and digging in the pocket for a clip … errrr…. magazine…, have one … or more … ready on a silver salver covered with a linen cloth about the size of a corporal. The altar boy, or if it is a more solemn occasion, deacon, can bring you clips magazines as you should need them.
The beretta should be cleaned after the purification of the chalice and before the final prayer and dismissal.
The congregation will be quite patient and will not leave before that final blessing, believe me.
[No actual extraordinary ministers of Communion or pop-combo members were hurt in the making of this blog entry.]