Dan, I have to say that you are often like a broken record. Whether it's breech plugs, touch hole liners or stock finishes, you establish an opinion and then hold on to it like your life depends on it. Just to let you know, it sometimes pays to be a little more open minded. Things are not necessarily how you believe them to be. You're far from the final word. Now I fully expect a page long diatribe on how guns breeched without a shoulder are unsafe, unfit to use etc. Please don't let me down 
Wow I guess I should not have taken all the stuff out of the other post.
You know what I could quote a friend: "if I have to explain this you ain't gonna get it anyway". But that might be "insulting" so I will try anyway.
I tried to explain how to do something right. This immediately must be countered.
Was I WRONG? If not whats the point of discussing threaded bores?
I am like a broken record because the "lets build a wall hanger grade gun then shoot it" mentality is like a broken record here as well. But if you are KNOWN to the people here some of the most incredible statements concerning REALLY frightening gun making "processes" pass without comment. I don't comment since I am from too far west and will be attacked if I say something unflattering about certain idiotic, frightening, statements I have seen here. As another poster told me "its impossible to know how to respond" to one such post. Apparently nobody else did either. I suspect that most did not understand the import.
I am pretty careful about nipple seats too. A surprising number of these blow out it seems. Poor design and fitting (that thread slop thing again I guess). But we probably should not go there or ask for a show of hands for how many people may have experienced it. BTW I did. Its one of the reasons I prefer flint.
Then there is my experience with sloppily made reproduction 19th century breech loaders and the scary things I learned about improperly fitted parts that are supposed, for example, to keep the cartridge case IN the barrel until removed by the shooter not auto ejecting cutting a groove in the shooters hair, honestly, this only happened to ONE of the people who reported this to me. Not related? Ill fitted gun parts are ill gun fitted parts. Blackpowder was still the propellant. Its astounding the things that can be gotten away with.
I tend to rant over things because I know of scary things that have happened to people.
I suppose people think that I just make this stuff up from thin air. Not so.
I started making guns as a teen. I bought parts and screwed them together. Breechplugs were often shorter than the threads in the barrel. I did various things to fix it until I finally learned that it is not supposed to be this way and that being in too big a hurry or being too lazy to get the gun done was not an excuse for failing to do it right. So I try to explain how to make things with more care and knowledge.
I use plastic finishes. I just put some on the window trim behind the lathe the other day. I figure its more cutting oil resistant and it was easy, never going to be outside, whats not to like?
I have SEEN what the plastics look like on friends stock work. Its not guessing. But nobody wants to do the testing to show that the stuff they use is brittle and will crack. Better to just keep using the stuff since someone else says its OK.
LOTS of guns have been and will continue to be breeched with no shoulder.
But like many things its SITUATIONAL some MUST BE breeched this way. EVERYBODY KNOWS THIS AND ITS BEEN DISCUSSED BEFORE. Some large bore pistols and other thin wall barrels sometimes don't have the wall thickness for a shoulder. Not wise imo but there it is.
I pulled original plugs from doubles in 1967+- and 1971 that were this way. But you know what? THEY FAILED TO INDEX WHEN REINSTALLED AND WERE THEN LOOSE . I think most people here know I know this was done and it was not part of the discussion nor was it needed but it gives someone something to counter with if I say a shoulder is the best way. Frankly its apples and oranges and YOU KNOW THIS. So frankly you can take your Chicksh*t attitude and stuff it. If you don't like my posts DON'T READ THEM.
Most rifle and other long gun barrels have sufficient barrel wall to allow a plug large enough to use a shoulder it need not be large after all. So GENERALLY for the question that was asked its best to shoulder the plug unless the BARREL maker taps the bore for the plug as some do or use a common drill for a tap drill then there is no shoulder in either case unless the plug is bigger than people of this ilk tend to use. So other than in certain situations where it really is unavoidable not seating on a shoulder is a CHEAP, SLOBBY WAY TO BREECH A BARREL. But of course this makes people uncomfortable if they make barrels that are tapped as described and it makes the people who use the barrels uncomfortable since they don't bother to fix the problem. Now vs then. Again.... Since it apparently did not soak in the first time.
I get the idea that people think that the breeches put in in 1770 or what ever have .005" or so "tolerance" in the threads we find in modern taps and dies. I think that this is an error for the most part (there are few absolutes). There is a built in slop in all modern threads, its called "interchangeable parts" this way a person can run the local hardware store and buy a tap and a bolt of the same size and thread, tap a hole and the bolt will screw in it. The bolt is a few thou UNDER and the tap a few OVER. Hey it fits and Joe 6 Pack is happy. BUT THESE THREADS WILL LEAK ANY FLUID PUT AGAINST THEM.
The only way to minimalize this if no shoulder is used is to:
1. grind a true bottoming tap that really bottoms at near full thread.
2. Make the breech plug with a expandable die so it has minimal clearance in the threaded hole. You cannot buy one that is this tight. So the average person who tries to do the tap the bore thing CANNOT DO IT RIGHT BECAUSE THE THREAD TOLERANCE IS WRONG. But of course the average person may have a little difficulty with this if the threads are cut out of line the bore which can happen. I start all such threading operations on the lathe then finish with a split die
Now turn the plug in carefully filing the the face and threads until the threads on the plug fill the threads in the barre and the tang aligns as desired.
But of course its easier just to screw a plug in and let someone down the road worry about it.
Its actually easier to put the plug against the shoulder if the barrel has sufficient wall, easier, works better. But we would rather argue that not ALL barrels are breeched this way.
The point of sites like this should be to try to advance the art not continue to make mistakes or recreate errors. I don't sing "if it was good enough for my Father it is good enough for me".
Just screwing the plug up into the end of the threads will not work well due to the slop in the threads.
BTW a "screw in the tap and then screw in the store bought plug" breech will also leak oil and even cleaning solvents into the stock until its fully plugged with fouling. But that don't matter I guess if enough plastic is soaked into the stock.
But of course if its CHLORATE fouling that is another matter.
So finally: Nope its not necessary to do it right. The threaded joints are generally so strong that there is no chance of it blowing out. People can live with locks that dribble out priming or fall off 1/2 cock and fire, yeah, saw that at a match, it was not repeatable with a couple of experienced gunsmiths looking at it, just a cheap mass produced lock. But hey, the ball missed the guys head by a foot or so, why worry? No harm no foul right?
People getting their faces cut by cap fragments because the people making the guns can't be bothered to make the breech right. Not any more work, they were just too ignorant to make it right and it would cost too much to fix now, if they even care. So its not safe to shoot for the shooter or those around them.
Drums that will break off since they are made of cold rolled with low charpy test numbers. Yeah it happened to me and some other people have reported it too. Is there a widespread call for better drums? Nope. Best not to talk about it. The thing only went through a storm door, not like it was someone's head or anything.
The list is a long one if people UNDERSTAND and pay attention. But if someone points out that is does not have to be be this way, that a change in process can fix it, someone will come up with the Three Stooges Grade "it works OK for me " or that's not 100% true" defense. After all they own or maybe made a POS just like this so it HAS to be OK.
It makes it very difficult to try to educate shooters as to what things should be when they already own some cheap POS that needs fixing. They get their back up. After all THEY could not be so ignorant as to buy something that is faulty. So the ability to learn gets shut off by ego.
If the thing DOES break the shooter will likely hide it since several fools told him, perhaps in some magazine article, how wonderful the thing was so it must be his fault. The same thing seems to occur with burst barrels. After all we all know it's impossible to burst a barrel with BP.
So I am sure just wasted a lot of time. I need to be on the road a 4am.
But like Churchill said if the point is worth making its worth pounding on (paraphrasing).
What is the position on the pressed in breechplugs some of the japanese made barrels had in them???
Dan
