.300blk Sig mcx snakebite (8 inch barrel replaced for a 6.8)
Gun was runnning like a top for about 600 rounds over 6 months+ and multiple range sessions. Suppressed, unsupressed, all on the minus gas setting, cleaned, dirty...it didn't matter, it ran absolutely flawlessly.
Then, Sig sent me a new trigger:
798681584543 1 KIT-
TRIGGER KIT, AR, SIG SAUER,
TWO-STAGE, MATCH DUO
Trigger was installed, cleaned the gun, and immediately at the next range session I started having issues with a round not being picked up from the magazine (empty chamber, click w/ no bang). This started happening in the middle of emptying a magazine...and then also occasionally on chambering (or trying to) the first round of a fresh mag.
This issue only happens when a suppressor is attached, and setting the gas setting to + seems to make it happen less.
I've tried this with both the included lancer mags, and magpul .300blk specific mags, stanag 5.56 mags, and magpul gen2 and gen3 5.56 mags.
I've had the trigger install looked at by 2 separate competent local gunsmiths, and compared it side by side w/ MCX's on dealer shelves, looks perfect.
I do notice some wear/drag marks on the bottom of the bolt carrier that I did not notice before the trigger was installed.
Of course Sig would allow me to send this back, but the problem is intermittent and sometimes doesn't happen for a couple mags...sometimes it happens every few rounds.
Does anyone have any idea what I could check - or if they've ever seen this issue on an MCX?
Have you switched back to the old trigger?
I'd start there to make sure it is, in fact, the trigger.
Nope, haven't tried that. <edit> In fact I'm hoping I don't have to do that as I'm not sure where I put the stock trigger, and don't want to hassle w/ and uninstall/reinstall.
Can anyone think of a scenario where a trigger would cause this behavior?
-FreqThis message has been edited. Last edited by: Freq18Hz,
If there is some issue with the hammer being out of spec or maybe the hammer spring, I could see it affecting the bolt cycling.
Is the bolt carrier dragging on the hammer?
My thought exactly. Marks on the bottom of the carrier that didn't used to be there, and only after a new trigger was installed? I'm guessing the hammer sits higher in the lower than the factory hammer, which is dragging against the carrier, which is forcing the BCG up in a meaningful way to overrun the round in the top of the mag.
The different geometry of the new hammer, combined with a potentially stronger hammer spring, could be causing just enough additional friction or pressure on the BCG to cause an issue. You're correct, this is a very strange problem.
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