On another thread, you made this observation:

"The Omega breech plug has an unthreaded nose that traps fouling..."

The Encore breech plug is the same, and I have often wondered why they were designed this way (most often when I'm cleaning the fouling out of the threaded part of the receiver opposite the unthreaded part of the breech plug).

Do you have any idea why they were designed this way?

The std. Encore and the Omega breechplugs are identical.

They have gone through three changes:

1) Original, deeply concave. But, easy to crush pellets.

2) Solid across-- but, T 7 fouling increased (but no crushing of pellets).

Phase 3) Similar to the original, but a ring at the perimeter for pellet support.


The unthreaded portion isolates the threads from close contact with hot gas.

But if the unthreaded part was threaded, wouldn't that also isolate the threads from hot gas and keep the fouling out?

quote:

Posted 09 October 2006 07:51 Hide Post
But if the unthreaded part was threaded, wouldn't that also isolate the threads from hot gas and keep the fouling out?

No.

?? Let me re-phrase the question. The front 1/4 inch or so of the breech plug in the Encore is not threaded, but the receiver (Encore frame) is threaded all the way. So the threads in the front 1/4 inch of the frame get fouled because the un-threaded part of the breech plug lets fouling in.

Seems like T/C could have solved the problem by threading the breech plug all the way, is there a reason they didn't do this?

quote:

Posted 10 October 2006 04:25 Hide Post
?? Let me re-phrase the question. The front 1/4 inch or so of the breech plug in the Encore is not threaded, but the receiver (Encore frame) is threaded all the way. So the threads in the front 1/4 inch of the frame get fouled because the un-threaded part of the breech plug lets fouling in.

I have no idea what you might be referring to. There are external breech plug threads, and internal barrel threads-- no "frame" or "receiver" threads at all that are in play.

right you are, I was referring to the internal barrel threads. The ones that get fouled because the breech plug nose isn't threaded.

As mentioned, the unthreaded portion isolates the threads from close contact with hot gas. That is the reason for the unthreaded portion on T/C breechplugs, and other even more robust designs.

Seems to me that if the entire breech plug was threaded, then the interior threads on the barrel would be more effectively isolated from the hot gasses and wouldn't get fouled at all. Seems like a design flaw.

I had thought that if the breech plug was threaded the entire way as you suggest, the threads that were added to the shoulder would then be in direct contact w/ the hot burning gases and would quickly erode causing difficult breech plug removal. I had further thought that having the threaded portion of the breech plug set back w/ the shoulder on its leading edge DOES prevent the hot burning gases from making direct contact w/ the threads. You will see a deposit of byproducts to the combustion process around this shoulder but that is the price of admission.

GVA

quote:

Seems to me that if the entire breech plug was threaded, then the interior threads on the barrel would be more effectively isolated from the hot gasses and wouldn't get fouled at all. Seems like a design flaw.

Exactly the opposite.

Gary, that makes sense, thanks. I guess the interior threads aren't used anyway, so they can be sacrificed.

The plug face/nose is designed that way to accept fouling/thus diminish blowback. That is why the flashole enlarges thru age - yet no powder blowback occurs at/thru the firing pin/hammer door. Threading the nose surrounding that concave cavity may eventually weaken metal integrity with magnum powder loads like 150 gr. 777 - plus create stronger plug seizures than we already see using hot powders like 777 and Swiss Black.

quote:

The plug face/nose is designed that way to accept fouling/thus diminish blowback.

Not at all. Internal barrel threads are not structural components-- anymore than rifling is. It is not "designed" to accept or attract fouling, nor does it decrease internal blowback.

It is very simple approach, and not new at all. Nor is it unique to T/C, Knight breechplugs have an unthreaded portion as well, with the Savage 10ML-II having a very large unthreaded portion. As many know, the Savage breechplug withstands over 129,000 PSI in all models and configurations. As gas flow and temperature decreases with distance, threads away from the powder charge simply do not see the heat or gas they otherwise would.

Many, many excessive pressure applications have been lab tested. Having an unthreaded portion is stronger than the alternatives of threading to the front, based on two primary findings:

A) Threading to the front would reduce the cross sectional wall (root to root diameter of inner and outer threads) and place stress risers at the area of greatest strain.

B) The area of elongation under stress would is very short (or nonexistent) compared to the length of the non threaded portion that absorbs the stress repeatedly over its length without exceeding the yield strength of the steel.

quote:

Originally posted by RandyWakeman:
Not at all. Internal barrel threads are not structural components-- anymore than rifling is. It is not "designed" to accept or attract fouling, nor does it decrease internal blowback.

Why is it that every ML messageboard you visit - you fail to read the prior posts properly? Do you need to consult a neurological doctor? Perhaps discontinue your practice of "speed-reading"?

Where did I state that the nose design has anything to do with internal threads?

The breechplug is an independent design. I also never stated that T/C "intentionally" designed the plug that way. What occurs to the nose-area upon ignition can easily be attibuted to an act of God.... meaning what occurs was never anticipated at the time of design.

With a topic like "Q for R. Wakeman--Encore Breech Plug" it isn't hard to figure out exactly who the question was directed at.

Having designed several breechplugs, of course I'm interested in the subject matter and can address it.