Bart, Carl & All-
The gun locks struck the quill primers that were inserted into the vents - that is why I posted the photos for you to see the different variations. The tops of the quills were filled with a compound of mealed musket powder, mercury fulminate and ground glass - the glass providing the friction when compressed by the hammer. Gun lock hammers were frequently brass, but the "nose" was made of case hardened steel or iron for obvious reasons. The problem that they had with the earlier locks was to get them clear of the vent - the heat & pressure of the gas jet was like a cutting torch. I think that Dahlgrens' improvement of Hiddens' patent called for the slotted hammer which allowed it to slide clear at the time of firing. Depending upon the type of gun, these gun locks were bolted or pinned to a bolster or "lump" cast into the top of the gun tube (Dahlgren) or screwed into holes drilled and tapped for that purpose (Brooke).
There are some photos here that will help you understand better what I have stated. In addition, I have included photos of the reinforce sight from S-65 - a piece recovered from Mobile Bay. The reinforce sight was mounted on a "mass" that was situated about even with the trunnions at the top of the tube. The photo of the banded 32'lb'er bow gun on the CSS Teaser really shows a lot about the working end of a large gun. Note the reinforce sight, elevating sight, improvised gun lock cover (dishpan?) and lock lanyard & toggle looped and ready for use.
Questions?