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Post by boarhog on Jul 12, 2009 13:04:32 GMT -5
Hope you can see this blurry pic well enough. Please note the white, burned powder, residue on the un-threaded nose of my new hex style Savage factory breech plug. I made certain that it was tightened snugly before starting to shoot. IMO, this settles the question of whether, or not, powder gases leak into the area. As a comparison, I fired a few shots with the original breech plug also. It has the same powder residue on it. Other than my drilling out the nose about 1/2 " to form a recess, the bps are OEM. I do not see any evidence of flame cutting on the shoulder of either plug, but the old model only has around 40-50 shots on it, and the new only has about 100 shots. As far as I can tell, the vent liners are still right at .031 since an .032 torch tip cleaner will not go into them. On the thread that discussed the TB Blowups, someone mentioned the occassional failure to seat the BP shoulder against the opposing shoulder on the barrel. As far as I can tell, Savage makes no effort to set these bps up to work that way. It is possible that all Savage ML10II rifles have lesser or greater gaps at that point, and that the ones with a larger gap may gather enough unburned powder in that area to push a load past MAX pressure. Especially if the shooter is pushing the speed/pressure envelope anyway. Hope I'm not starting another one of those Goat Hunts!
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Post by Dave W on Jul 12, 2009 13:18:35 GMT -5
Every plug I have ever used does the same thing BH.
For the guys that shoot BP subs and tape the nose of the plug, would thread tape stop the leakage?
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Post by boarhog on Jul 12, 2009 13:34:57 GMT -5
Based on my recent attempt to shoot .500 dia bullets sabotless by wrapping the bullet with teflon tape, I can't see how you could get a tight enough seal to do much good. Enough tape to be tight would catch on the sleeve area that the nose fits into.
I have also been thinking about those pics of washed out bp shoulders. A wider gap would probably flame cut less than a narrow. The narrow would increase the speed and heat of the flame/gasses just like a water hose nozzle increases the pressure as it reduces the opening.
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Post by pposey on Jul 12, 2009 14:40:58 GMT -5
but a wider gap could let powder through, that might be worse
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Post by boarhog on Jul 12, 2009 15:47:04 GMT -5
PPosey, Exactly my point! I was also thinking about something like an O-ring around that smaller nozzle area. Similar to an auto exhaust pipe donut gasket, but obviously small enough to fit the end of the b plug.
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Post by jims on Jul 12, 2009 15:58:21 GMT -5
I do not recall my breechplugs looking like that. What powder and primer are you using?
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Post by Richard on Jul 12, 2009 16:10:19 GMT -5
I can tell you right up front, that an "O" ring is not going to withstand the 30 - 40,000 psi. I had thought about something on the idea of a "spark-plug type" washer....possibly a brass or copper washer at the base of that little snout on the BP. I don't get any white on mine, only a black coating that will rub off with a rag. To do any type of a washer, you would have to re-headspace the barrel or undercut the BP. I mentioned brass or copper because they are somewhat soft and would conform more easily. I would think that if Savage did not want any pressure getting beyond that snout, they would have either engineered that differently or provided some type of sealing washer. Which leads me to believe that the threads are the main barrier to keep pressure from the area behind the BP. Richard
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Post by boarhog on Jul 12, 2009 16:36:46 GMT -5
Richard, I have been using N-110, 4759, re-7 and a while back, shot a few loads with H=4198. Some of the residue is whiter than others, but always some sort of it. Today, since it was so white, I decided to take a pic to post. I also thought about some crushable washer or gasket. I knew that a rubber O-ring would never take the pressure.
I think we agree that Savage considers the threads to be the pressure barrier. My guess is that every Savage has a different space or gap at that point, depending on how far the barrel is screwed in to set head space. Or maybe that is Primer space?
I would be willing to bet the contents of my very hungry Piggy bank, that all the blow-ups we know about can be attributed to the shooter trying to push max speed. Perhaps doing so over time until metal fatigue works it's magic. I say metal fatigue because of the way the Oehler Strain Guage works to do the pressure traces. I am pretty certain the chamber area actually swells some amount at the shot. The question is, do max loads swell it enough to weaken the metal at a molecular level?
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Post by ozark on Jul 12, 2009 18:25:16 GMT -5
Although zero leakage would be ideal, I can't believe that some causes a dangerous situation. I know it causes that portion of the BP to rust quickly and is not pretty but the real questions is: Is there any proof that this leakage has caused an unsafe situation? As some have mentioned BPs have become loose obviously leaving a clearance for gas to leak into the area without mishaps. It is an interesting point to discuss and I have read some profound thoughts on the matter. But I personally believe that it is safe even if some leakage occurs.
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Post by chuck41 on Jul 12, 2009 22:04:30 GMT -5
I once had a brainstorm. Coat that area of the plug with a good grease and that would fill the area allowing no blowby and preventing difficult removal of the BP. Guess what, it works! However after the forth or fifth shot some of the grease manages to get to the vent liner area and wets the powder causing it to go "poof" instead of "Bang". Not exactly what I was looking for. However, the breach plug was really easy to remove afterwards.
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Post by boarhog on Jul 26, 2009 19:58:40 GMT -5
This thread probably should be moved also.
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Post by Jon on Jul 26, 2009 20:11:43 GMT -5
Just a question, Asbest as I can tell the smi bp seats at the back and the threads are exposed o direct pressure. How many of them have blown up? Jon
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Post by Dave W on Jul 26, 2009 21:15:15 GMT -5
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Post by rossman40 on Jul 27, 2009 9:42:24 GMT -5
The engineering behind the plug is more then simple. You have the nose of the breechplug going into the rifled bore. The nose is like .490" with the bore of the barrel .508", so basicly you have a .010" gap. You could tighten this up but you would have to have pretty tight tolerances to be able to have field swapability. For the chamber pressure to get to the threads it has to make two 90 degree bends, this is the labyrinth seal that Edge has referenced in the past. It will not stop pressure but will slow it down and we are talking a event that last milliseconds. Then we have the area along the snout, much as the way the vent works it is pressure over time. Even with some leakage past the sealing area by the time this area can even start to come close to chamber pressure the chamber pressure is already on the downhill side. The threads for the Savage breechplug are fairly large diameter but they gain strength by having the threaded portion in the area of the receiver ring. If you compare Henry's early design the threads are a smaller diameter. Threads are not a great seal, that is why pipe threads are tapered. Every shot the gases will try to follow the screw threads and if you get carbon blowed in the threads removal will be tough.
As far as a sealing washer with material soft enough to get a good seal, if gas even starts to get past it the gases will eat it for lunch.
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