Sig MPX/Hyperfire 24c issue

[Nimitz]

I installed a Hyperfire 24c drop in trigger into my MPX and have put 800-1,000 rds through it with no issue --until at today's match.  At the start of a stage I could fire the first round & then after the case was ejected & another rd loaded I would just get  a 'click' like a light strike.  Cycling the bolt would eject the round, feed a new rd and then you could fire another shot.  However, on the next round the exact same thing would happen - I basically now have a single shot MPX --lol.

 

A little digging into it and we discovered that after the first rd fires the bolt fails to close all the way, by about 1/32" to maybe as much as a 1/16".  However, the trigger resets and you can pull it even though the bolt is not fully closed.  Cycling the charging handle ejects a rd, chambers another one & fully closes the bolt, allowing you to fire it.  Also, pulling the bolt back about 3/4 & letting it fly would close the bolt completely.  I tried someones factory ammo vice my reloads (~130 PF) with the same result.

 

Anybody ever seen this or have any idea what issue would allow the trigger to reset but not fully close the bolt?

[L3324temp]

Is the gas system cleaned well?


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[2011BLDR]

is their any penining on the carrier either front what the bolt rotates or at  the rear around the  firing pin?

 

Edited April 8, 2018 by 2011BLDR

[mikeAZ]

Sure sounds like your ammo... Do you case guage every round?... Have you recently changed bullet brands?..I "paint" a round with a red majic marker then slam chamber it and check for scrapings on the marked round... Since the gun has been running before seems something has changed???

[Ming the Merciless]

Bolt travel is only 1.4" to cock the hammer and release the disconnector, resetting the trigger.  With an empty chamber, drop the hammer and hold the trigger pressed, then slowly pull the bolt back about half an inch and release the trigger, continue slowly pulling the bolt back until you hear the disconnector release the hammer.  The front edge of the bolt carrier will just be even with the rear edge of the ejection port on a Gen. 2 MPX.

 

I would look at the gas piston being dirty and sticking, or the bolt carrier being gummed up and causing the bolt to stick.

 

When you cycle the bolt by hand, I would guess that you draw the bolt back fully and then let it fly forward giving it enough momentum to drive the sticky bolt/gas piston into battery.  When you fire the gun I would suspect the bolt is just traveling just far enough to eject the empty and pick up a new round.

[Nimitz]

thx.  I'll try those suggestions & then look at the gas port.  How often are you all cleaning the port?

 

Pretty sure it isn't ammo as the first thing we did is try someone's factory ammo vice my reloads & exactly the same thing happened ... also I was using exactly the same ammo as below just with a higher PF (same bullet, same OAL)

[Nimitz]

Can't seem to get the gas valve and tappet removed ... Can someone tell me how to do this?  The instruction say to use a punch in one of the holes and rotate the valve until the flange is free and clear of the gas block but nothing moves ...?

[NervousEnergy]

I clean the gas system every third match, so 500-600 rounds (everything else is after every match).  The fact that it's not moving at all is making it more likely your culprit.  ;-)  I haven't had an issue getting mine apart, though it can be reluctant to move.  Mine's not been THAT difficult, though, even on the first cleaning.  Have you hit it with your CLP of choice? 

[edwin garcia]

Youtube MPX Gas Valve

Used this as a guide. Mine was a little tight on first disassembly. I fist disassembled and cleaned mine after approx. 300 rds and it was somewhat tight.

I cleaned it again after approx. 500 rds and it was no where hard compared to initial disassembly.

I'm trying to push it to a thousand round or so as one of our local shooters seem to think it can push to that schedule.

Best of luck.

[Nimitz]

ok thx.  I had put 800-1,000 rds through mine prior to this issue so assuming its a dirty gas port I suspect you may not be able to go that far ...

[Nimitz]

well, at least i know what the issue is ... lol.

 

Had to use a hammer to bang on a crescent wrench locked on to the front of the valve to get it to loosen & rotate.  Unfortunately even after pulling out the valve the tappet wouldn't budge due to all the carbon caked on it ... I'm soaking it in some bore cleaner to hopefully loosen it up & then thoroughly clean it.  The end of the valve which goes into the port on the barrel was also caked with carbon ...

 

looks like I'll be cleaning the gas port a lot more often ...