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TM G17 - Top slide locks back and 'off' the rail


Amenthea

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Hi,

So my rather old (4 years plus?) TM G17 kinda exploded on me after gassing up and checking it still worked after the not being used for a few months.  I'd stripped, cleaned and oiled/lubricated it as per usual, and gassed up the mag.  Everything seemed fine and then when I fired off the first round there was way too much gas venting in a rather loud crack, the rear sight flew off and the slide locked back.  I found the rear sight, and found it was cracked.  The screw had come out and had come off during the shot, also making the blowback unit loose in the top slide (as the screw holds it in).

 

As I thought it was just that, and it was just loose, I picked up a replacement rear sight and fitted it as required.  Checked over the blowback unit at the same time and everything else, all looked good, so popped it all back together and racked the slide a few times with the mag out.   It was smooth as per usual I gassed up the mag again and let off a shot and lo and behold, lots of venting and the slide goes all the way back and comes up and off the guide rail and gets stuck  (see attached image).

 

I have no idea why it's doing this to be honest.  There are no visual clues to there being anything wrong after I've replaced the broken part, so I can only surmise the mag is kicking out too much gas per shot, the blowback unit is doing something similar, or the gas I'm using is waaaay to strong for it.  (It's ASG UltraAir Power Gas, I've been using it with a TM Sig 226 and TM Foliage Warrior for years with no issues).

 

Any ideas?

post-61302-0-26007700-1506545416_thumb.jpg

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ABS Glock slides are just a bit more bendy sideways from lack of rear support unlike 1911s and SIGs plus they can get softer with age. Totally not recommending this unless you know what you're doing, but you can take a heat gun to the inside of the slide just enough to reform it to have a slight pinch (and I really mean slight or it will impede slide movement) to better grab the guide rails.

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venting is caused by the slide failing to disconnect the valve locker, or by a massive gap between the nozzle and the magazine output release valve. Both of which can perfectly be due to the slide coming up. 

You need to completely disassemble the blowback unit and check for proper function, and completely disassemble the hammer unit and check for damage there. I've had brought to the workshop a TM G17 with a similar problem that turned out to be a cracked hammer assembly housing.   

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