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  #41  
Old 12-13-2018, 02:33 PM
1961bama 1961bama is offline
 
Join Date: Feb 2015
Location: Florence, AL
Posts: 28
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Quote:
Originally Posted by DaveHH View Post
Just a few things that I think about: Comparison of a carbine using 15 gr (a tiny amount) and a cannon using pounds of explosive powder is probably not valid.
If the pressure is so great, why is the piston located so close to the chamber? And why is the gas chamber so large? A Garand has the gas port at the muzzle and the chamber is tiny.

I would try a lot of stuff before changing the barrel.
I was perfectly willing to stay gone but alas...
Come on guys, think. A carbine explosion takes place inside the sealed case initially not the barrel, sealed by the crimped round... just like a hand grenade going off and you know what that can cause.. At the time of the Civil war cannons used round balls in, impossible to sea, cast barrels kinda like pouring powder on the ground and lighting..still many barrels were ruptured.
I think you are absolutely right on the barrel, the gas cyl needs replaced(and that is no big deal) not the barrel....... Hope to stay gone....
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  #42  
Old Yesterday, 03:46 PM
Tuna 1 Tuna 1 is offline
 
Join Date: Oct 2009
Posts: 935
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The operating pressure was originally 30,000 PSI. This was increased early on to 40,000 PSI. Now the US military for years tried to weld gas cylinders and FAILED. The weld if it held was be OK but the gas cylinder would crack close by the original crack. They came to realize the best bet was to replace the barrel if the gas cylinder did crack. It was quicker, easier and cheaper in the long run to do it this way. And the gas cylinder would be fine till some idiot over tightened a castle nut and cracked the cylinder. That is why the system was set up so only ordnance was allowed to touch the gas system on a carbine.
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  #43  
Old Yesterday, 07:59 PM
eric_robin eric_robin is offline
 
Join Date: Sep 2018
Location: Huntsville, AL
Posts: 175
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Quote:
Originally Posted by Tuna 1 View Post
The operating pressure was originally 30,000 PSI. This was increased early on to 40,000 PSI. Now the US military for years tried to weld gas cylinders and FAILED. The weld if it held was be OK but the gas cylinder would crack close by the original crack. They came to realize the best bet was to replace the barrel if the gas cylinder did crack. It was quicker, easier and cheaper in the long run to do it this way. And the gas cylinder would be fine till some idiot over tightened a castle nut and cracked the cylinder. That is why the system was set up so only ordnance was allowed to touch the gas system on a carbine.
Still waiting on my carbine to begin the project... (simple shipping issue) I do have a donor barrel stub to practice the weld on though.

Question - does anyone know root cause for this defect? So far I've heard (1) high carbon steel used (2) over-torquing the castle nut (3) poor design (4) 30 rnd. magazines promoted high rate of fire and (5) some just failed...

Any idea? I'm tempted to fill in the drilled hole thinking the original angled drilling for the barrel hole creates the situation for the crack to begin... and over-torquing the castle nut / high rate of fire just seals the deal.
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  #44  
Old Yesterday, 09:46 PM
Sam Hamburger Sam Hamburger is offline
 
Join Date: Mar 2016
Posts: 34
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Just thinking out loud. Another possibility might be a shooter who loads the piston with oil. On firing the first round the flash over will cause dieseling that can really bump the piston. I have seen this on low pressure, break barrel air rifles. You can hear the knock or crack.
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