With regard to Removing Breechplugs during the building process.

[Razor62]

After reading another post who's author was concerned about removing his breechplug in order to properly bed his barrel. I was hoping to see some info regarding a problem that plagued me and I thought that it was something worth noting... I've got very limited experience with fitting breechplugs but on my last build I ran into a problem after removing a breechplug that I had carefully fitted to my barrel. I found that after uninstalling and re-installing the breechplug a few times that I had to go past my witness mark in order to snug the plug up tight. This posed many problems as you may have guessed. I ended up making a thin shim washer of brass in order to get my plug aligned properly. The problem was that the threads would crush somewhat when the plug was tightened to final torque thus causing me to have to screw the plug in a hair further each time it was re-installed. Perhaps I had overtightened the plug but I don't feel as though I did. I'd say that once the plug began to snug up just a little, I was left with about an eighth of a turn to bring my flats into alignment and this required only moderate pressure while using both hands on a 12" Crescent wrench.
How do you folks avoid this problem when installing and removing breechplugs repeatedly during a build? Or perhaps a better question is what was I doing wrong?

 

[Lock Nut]

Also in that post there was a lot of concern by some for checking that the plug was properly installed as no one seems to trust the work of others. I get the safety concern but I wish someone would post in detail how this is done and just what exactly are you looking for to insure a properly fitted plug and why.
Also, as in your case what to do in the event of correcting a situation that can pop up such as yours.

Just curious, has anyone ever had or seen a breach plug blow out from being improperly fitted?
I get the pressure that builds up in there but one would think the patched ball or even a liner would blow out long before a breech plug. :hmm:

 

[galamb]

If it would "keep turning a little further" each time it was installed it was not timed correctly.

I suspect that the thread portion of the plug was too long (my first guess since you noted crushed threads at the end of the plug).

So while initially the plug face "bottomed out" in the breech, there must have been a "hair" of gap between the plug and the back of the barrel (without the little gap you wouldn't be able to turn significantly past the match mark).

If a tiny gap was present it allowed the plug to "travel deeper", and with the threads being the weakest part (particularly the last thread butting against the face) it "crushed".

This all arises out of the fact that the barrel makers use different depths for the threaded portion of the breech and with the makers of plugs there is, likewise, no "standard" other than the size and tpi.

So the breech portion of a Green Mountain barrel is .625", Colerain goes about .550" (and sometimes Rice, my latest Rice was .497" etc.

Many plugs have threads +/- .500/.550'ish - but again, until you put a caliper on it you never know exactly.

This why I time my own plugs. If the barrel had a .550 deep breech and the plug grabbed out of the box was .500 and it was close to coffee break and it was screwed in, the rear of the plug would snug up nice at the back of the barrel and it may get shipped that way (with a gap at the face)

OR

like (I suspect) you have experienced. The breech is actually a tiny bit shorter than the threaded portion of the breech.

So it's tightened in, it's snug against the face, but that little "unseen" gap exists at the rear which WILL allow you to torque it in tighter, destroying the front threads in the process.

Before the plug/barrel is match marked the installer should be absolutely certain it's timed correctly.

If you install the plug, then remove it to check and the front thread is crushed - the plug is "too long".

If you measure it and the breech and it doesn't go in all the way you probably have to relieve the back threads of the barrel a little (chamfer it) - if the plug is not threaded all the way to it's base, it can hang up.

Or, the bottom of the breech may not be finished fine enough requiring the use of a bottom tap to clean it up - in almost every barrel I have done I have found a small "burr" leftover from the machining process - this must be removed or the plug will never fully seat properly or it will chew up the plug face causing a fouling trap.

This is exactly why, even if you have your barrel breeched by a trusted source, that YOU check it before you start installing.

This situation "really sucks" if you have quite a bit inlet and then realize you have to re-time the plug which means either changing which flat is on top/bottom/side etc OR going one more complete turn with the plug which could leave gaps with a swamped/tapered barrel.

IF the face of the plug bottoms out in the barrel at exactly the same time as the back of the plug snugs against the back of the barrel you should NOT be able to turn it past the match mark unless you use GREAT force, way beyond what is required AND you should not deform/chew up bottom threads - load them, yes, crush them no.

 

[galamb]

Just curious, has anyone ever had or seen a breach plug blow out from being improperly fitted?

I have never seen or heard of a plug blowing out.

Personally I don't see that as an issue - unless the job was botched to some severe degree the threads are going to keep the plug in the barrel.

But what can happen:

Gas cutting - where gas from the barrel starts cutting a channel through the threads because they are not tightly sealed.

This would be noticed before it became life threatening but could result in damage to the barrel as well resulting in a rebreech or replacement (as well as the damaged plug).

Rusting - if the bottom of the plug does not snug against the face of the breech the resulting "gap" will trap fouling and other cooties that can cause rust - again, the rile will probably be "shootable" for a while but it will ultimately destroy the plug and the barrel and does leave a weak spot at the point of maximum pressure in the barrel, a mere 2 to 3" from your face.

 

[galamb]

I get the safety concern but I wish someone would post in detail how this is done and just what exactly are you looking for to insure a properly fitted plug and why.

Checking it is relatively easy.

The first thing I would do is try and tighten it a little more.

Clamp the barrel in a padded vice and put a well fitted wrench on the breech plug. Exert some force - I don't mean put a 3 foot breaker bar on the wrench and lift yourself off the ground, but most of us can determine "tight".

So, if that doesn't move you can be rest assured that the plug is well mated to the back of the barrel.

Now you need to ensure the face of the plug is mated to the shoulder at the bottom of the breech.

So, make sure it's match marked (or do it yourself now), then remove the plug.

With the plug out take a black magic marker and "paint" the entire face of the plug (any metal marking product is fine).

Now re-install the plug to the match mark.

Remove it again and check where you painted. You should see a ring around the circumference of the plug face where the marker was rubbed away by contacting the shoulder of the breech.

If it's not uniformly rubbed away in a nice ring, there is a gap.

If it's not rubbed away AT ALL, there is a BIG gap.

If it's a nice uniform ring and the bottom thread on the plug is not crushed or deformed it is timed as near perfect as you can get.

 

[Razor62]

Thank you GALAMB. Very helpful info. I'll try to be more careful in the future when installing the plug. I did use your methods however with the gun in question but I guess I missed something. Pulling that plug should tell the whole story.

 

[Lock Nut]

I guess this can be a major problem if you have a barrel with run out or has the dove tails already milled in.

 

[galamb]

This is why it needs to be checked "before" you start inletting.

If there is run out you want to orient the run out as "either" the top flat or bottom flat.

That could add a couple of steps the process.

Likewise, if the breech is deeper then the threads on the plug itself you are going to have to take some metal off the end of the barrel (almost always the case with a Green Mountain because they drill it to 5/8" and it's rare to find a plug with more than 1/2" of thread.

If the dovetails are cut in already you need to go in upwards of a complete turn to correct things - which means taking some off the plug and some off the barrel (done that myself on one barrel that I jiggered by working when tired and not paying attention).

In any event the process is tedious, but not beyond the capability of just about anyone who can hold a file and use a caliper and a machine square.

I don't have a lathe which would make things definitely easier, especially when you have to take .125" off the back of a GM barrel to get the breech to (initially) a workable length.

But with a file or two, lot's of trial fitting/measuring (I mean sometimes it's just one or two strokes with the file when you are getting really close between checks) it can be done.

And after the first one you gain confidence and insight (which is maybe why some plugs are poorly fitted by guys doing them "all the time", you could get complacent.

Barrels from most of the makers now should not have any run out. They are bored first and then machined on centers, unlike years past where they were bored after being shaped - so not a concern with most that you will buy "new" today.

And if you are not particular about where you have the makers mark oriented (most put something on the barrel to identify the mfg) you may not have to go back and forth filing the plug then the barrel etc.

When I time it in as long as the marks are "out of sight" - so on the bottom or either oblique lower flat, I'm happy with that - particularly if I'm well pleased with the fit.

I like the plug to wind in until about 1/2 to 1/3 of a flat is left before I want it to end up with slight pressure and then torque it that last little bit to load the threads - has worked well for me so far.

 

[Lock Nut]

Thank you for posting all that. I'll definately take a closer look at them.

 

[Vaino]

I use Rice bbls and have checked the breechplug timing on every one of their bbls and have never found a discrepancy.

Have also used a couple of Colerain bbls in .54 cal in which they use 5/8-18 threads which results in a .040 ledge for sealing....a bottoming tap is very important w/ this situation. If the chamfer at the sealing end of the plug is too large, little or no seal will be achieved. The .040 ledge could also be compressed by over tightening. In both cases, the contact at the breech end would be the only "stop" for the breechplug and could cause over riding of the alignment lines.

Rice uses 3/4-16 threads for the .54 which results in a much wider sealing surface.

There's no "mystic" asre breechplugs, but some are hesitant to remove them....which is necessary when building.

As far as the force exerted on the plug threads....bore area in square inches times the max pressure {PSI}. For a .54 cal... .250 square inches times 20,000 PSI {big load} equals 5000 lbs. Nowhere near the force needed to strip the threads.....Fred

 

[okawbow]

Personally, I wouldn't buy a breeched barrel if I wasn't confident that the barrel smith knew what he was doing, and had properly installed the breech plug. I don't remove the plug at all during my build. Would you remove a plug from a finished rifle you bought, just to "be sure it was installed correctly"? Would you buy a gun that may not have a properly installed breech plug?

 

[Vaino]

Nobody is perfect and that includes people who make bbls. If someone doesn't ever remove the breechplugs from their builds to check whether the threads, etc. pass muster, can't understand how a TH liner or just a TH is finished from the inside. Unscrewing a breechplug is so easy......and having been in masnufacturing all my adult life has taught an invaluable lesson....don't trust the manufacturing process. Of course, do what you will.... but again it's so easy to remove a breechplug and be certain that it's properly installed.

Asre buying a finished MLer.....be rest assured that a reputable builder does debreech and check the breechplug....I just couldn't sell my LRs w/o knowing that they're properly breeched.....Fred

 

[Birddog6]

Everybody builds diffferently. As for me ? there is No Way I would build a rifle & not remove the breechplug.

1: I want to be 100% sure of the fit.

2: I want to swab that bore with a Tight Oiled Patch with a cleaning rod with a bearing in the handle, and FEEL the bore & insure there are no tight spots or loose spots in it. The best way to do this is with the breechplug out.

3: I prefer to inlet the barrel to where I want it, then add the plug/tang & inlet it. Does not have to be done that way, but I just prefer to do it that way.

4: When I do the vent hole or vent liner, I want to SEE up close what the inside of the bore looks like there & clean off any burrs at that hole. If it is just a drilled hole, I want to cone the inside of the bore side of the vent hole. If a vent liner is installed, I want to insure it has no rough edges inside & fitted properly. If you have an issue there, you may not see it 38-46" away looking down a bore. Using a bore scope ? You may see an issue, but the scope will not fix it.

5: You are not buying a rifle & inspecting it afterwards. YOU are building the rifle & YOU are the final inspector that should should make sure all of the work is correct..... Don't assume Anything.... including breeching. :shake:

Having used quite a few barrels, I have found ALLOT of them not correctly breeched. Because of that, I ALWAYS check the breechplug fit. I have bought over 50 Rice barrels alone, and every single one was properly & precisely breeched. But I STILL check them & make sure, regardless of who made the barrel. This way I KNOW & there is never a doubt in my mind it was correctly done.

Keith Lisle

 

[galamb]

The very diverse opinion on whether to remove a plug or not results in a line which can be clearly drawn between those that are builders (whether hobby/pro/semi-pro) and those that have exclusively owned factory built rifles.

Would I remove the plug on a finished rifle I bought? -

I can't answer that because I wouldn't buy a finished rifle under any kind of normal circumstance. If I acquired one I almost certainly would tear it down to make sure it was safe/done properly especially if I hand any inclination to load and shoot it myself.

If I was a lottery winner and had someone like Bill Shipman or Peter Alexander build me a rifle I would have 100% confidence that the plug was in correctly. I know both would have installed/removed the plug a dozen times or more during the build.

Now if it was some "un-named" contract builder for one of the budget sources I definitely would want to take a look.

When you are looking at "unique" rifles it's not like something off a production line where every one is almost exactly the same built with possibly computer controlled machinery.

It's still "a guy/gal" sitting at a bench with a file and chisel and susceptible to making an error due to complacency, ignorance, distraction or any dozen other things.

So while you may not be worried specifically about your safety, aren't you at least worried about protecting your investment?

Heck, even when you buy a new car from the factory the dealer still burns you for the cost of a Pre-Delivery Inspection, just to "make sure" everything was done the way it should have been...