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I have an MCX in 5.56 with recall that was implemented several years ago. Two times today while shooting, the floor plate to the magazine blew out, and smoke and powder spewed out from the breech. Magazine is the common gray, aluminum (?) magazine mfg'd in Hartford, CT. Ammo is factory Federal, 55 grain ammo, FMJ. Gun didn't jam, fail to feed, or fail to eject either. This has never occurred before, and I am probably at around 1,000 round count. So, what's going on?
Posts: 84 | Location: Alexandria, VA | Registered: May 03, 2004Reply With QuoteReport This Post
sick puppy
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Two times today

Twice?? Id have been done after one! That is usually indicative of an out of battery kaboom, squib, case rupture or similar big-time kaboom when the explosion comes back and down more than it can go out the other end. While the Magwell does direct the gasses down into the mag and away from the shooter, it can mean parts breakage elsewhere.

Either your mag is just REALLY shitty and can lose its baseplate with the smallest of pressures (like... just being loaded) or there was a catastrophic failure in there somewhere.... what did the spent brass look like on each failure? No apparent damage on any of the parts? Bolt, barrel, gas system? What was the gas system set to? I know the MCX has different settings.

While you may be able to get away with bottom shelf whiskey, stay the hell away from bottom shelf tequila. - FishOn
Posts: 7291 | Location: Alpine, Ut | Registered: February 17, 2010Reply With QuoteReport This Post
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Sounds like an out of battery ignition?
High primer / bad ammo.
Broken firing pin. (rare).

End of Earth: 2 Miles
Upper Peninsula: 4 Miles
Posts: 8600 | Location: Marquette MI | Registered: July 08, 2014Reply With QuoteReport This Post
Doin' what I can
with what I got
Picture of Rob Decker
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Dude that sounds like textbook out of battery ignition. Have that rifle checked by a competent gunsmith and/or SIG.

Impressive that it apparently survived not one, but two, incidents.

Did you recover any weird looking brass? Are there any loose primers in your lower or around?

Some years ago I had problems with a combination of high Florida heat and humidity, a slightly overtight chamber, and hot AE XM193. It manifested in blown primers.

Seriously, I would not fire that ammo or that rifle again until I had contacted both manufacturers and determined what the problem was. The next failure might be catastrophic. Like, no more rifle, maybe a trip to the ER, catastrophic.

Death smiles at us all. Be sure you smile back.
Posts: 5301 | Registered: May 11, 2004Reply With QuoteReport This Post
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