hello again,
you do not want to mix 'chicken-little' repairs with firearms that go afield with you. it's probably enough of an inconvenience to suffer at a shooting range when something breaks; but in the field it could cost you meat........
do not mix aluminum with the repair you contemplate. the ''electrolysis'' that results from steel and aluminum (dissimilar metals) causes rusting of the steel. unlike aluminizing as is done with mufflers and exhaust pipes, the use of an aluminum nail, screw, or sheet alongside of steel is a problem.
the auto supply store or a machine-shop supply store should have your tap.
msc industrial supply company has all kinds of taps in their book. they deliver by 'ups'; and may drop it off to where you work if they have a field-rep' working in your area.
ss'