Breech plug question

[melsdad]

I received my barrel and plug the other day. I have seen in pictures of breech plugs that there was a cup machined in the face of the plug. The plug I received is flat faced. My question is should the plug be cupped, or left flat? If left flat I definetly need to smooth up the face some to remove machineing marks.

[Captchee]

a cupped face is the  so called improved  breech . it will then have a flash channel that goes back to another channel   from your flash hole . what you have is a standard breech . whats important is that it mates properly to the inside of the barrel so as to seal the threads . your flash hole will then be drilled just a tad forward of the breech face

[gunmaker]

Is the plug mated to bbl. by seller??  If not make sure it goes in no more than 1/2"  some plugs come way over that.  Yes as Cap says the vent threads should just miss the face of plug. The reason for all this is so Rear lock bolt will GO THRU tang ext. & NOT rear of bbl.. Bolt thds in lock bolster behind pan.  Pic's.   ....Tom

[melsdad]

Thanks guys. Yes the plug was mated at Rice. THe plug is not tightened though. I inspected the depth of the threaded counter bore, and the length of the threads on the plug. There is a .002 interference fit between the 2. Looks like an 1/8 of a turn will line up the top flats and seat both face together properly.

So what you guys are saying is leave the face flat.

[Captchee]

yes leave the face flat .
 If LC did the breeching then there also should be an index mark . IY a mark on the bottom flat that will align with a mark punched in the   bottom of the plug .

[Hank in WV]

Mark the face of the plug with a magic marker and tighten it in the barrel. Just sneak up on the witness mark. You don't want to go past it and stretch your threads too much. When you take the plug back out, there should be a ring all the way around the edge of the face if its' seated properly. I like to polish the face of the plug to resist fouling build-up.

[melsdad]

Captchee, when I received the barrel the plug was only finger tight against the shoulder of the barrel. This is how I asked to receive the barrel. I wanted to do the final fitting myself. There are no reference marks yet.

Hank, That is what I was getting at about removing the tool marks on the face. Polishing the face will help with cleaning.

[Captchee]

ok so  , your then going to have to face the breech yourself . like hank said , you want to  blacken the  face and edge of the first thread and front mating edge of the plug .  Tighten the plug down , then back it out . When the plug is faced  correctly it will show signs that the  front edge has came into contact with the shoulder . IE the black will have been removed evenly around the face of the plug .
 This has to happen at the same time as the back of the plug contacts the back of the barrel  and the same time you end on a barrel flat