Help with Vent Hole Liner ID

[BruceH]

I have the below vent hole liner in a barrel I got. It is a replacement and whoever replaced it also drilled and tapped out the hole to enlarge it. It appears they wanted a percussion/flintlock interchangeable system. Everything works fine, but I would like to have some spares on hand.

The threads are 5/16-24 for sure. I thought it was the RMC liner that uses the Allen wrench system so I ordered some of those. The head on the RMC is not as big as the head on this one. If anyone has a clue as to who makes these, I would sure appreciate a lead. Thanks in advance

[Daryl]

2 1/2 threads?? 🤧
I wouldn't use one

[BruceH]

I understand.  Not sure if they come that way or not.  The RMC has a lot more threads, but does not cover the inlet.

[Daryl]

That recess between the threads and the countersink angled
Top, rooks like something from an Indian musket's breach. The thread count is about the same as well.
Check out Whitelightening breaches at Chamber's Flintlocks.