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38 Posts
Discussion Starter · #1 ·
Got my MPX yesterday. Got it home, total disassembly, cleaned it (piston, barrel BCG, Trigger) and lubed it. Went to the range today with 500 rounds. Mostly Fiochi 124 and 115 grain and some CCI Blazer Brass 115gr.

1st mag full was awful, FTF, double feed, jams, got a shot off and FTE. So I checked everything and it all looked good. I unloaded the mag 1/2 way and it would fire a few and either stove pipe or FTE, cleared, then a few more off and a double feed.

This went on for around 100 rounds. It would cycle better if loaded to 10 rounds. Then around 175 rounds at 10 round mag load on the 30 round mag it cycled I would up it to 15 rounds in the mag and work that.

Finally after around 250ish rounds I could run through 20 rounds in the 30 round mag no problem. So I upped it to full 30 rounds. Sometimes it would feed the 1st round sometimes not.

Then around 325-340 round it started feeding a full mag no problem. from 350 rounds to 500 round zero issues...perfect running MPX.
I have 4 more mags on order and they should be here in a couple days. I am thinking it was mostly a mag issue because I noticed by the time I got to around 300 rounds the mag seemed easier to load and to just push bullets out with my thumb too.

I hope I don't have to go through 500 rounds per mag just to get the mags to work...LOL
Also the iron on..I was ready to adjust with sight tool but nothing needed...WOW! Target was on pistol range at 25 yards..standing no rest.

I am still confused if its legal to shoulder this pistol. I'm a big guy 6'6" 225lbs and I can cheek weed it but brace is not into my shoulder.


Premium Member
453 Posts
I went through the same thing with my MPX and my six mags. All sorts of problems until each mag was broken in, but as soon as they were broken in, all six magazines function flawlessly.
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8 Posts
In total that's about what it took for mine to run without a hitch. Only difference is you got there much faster! I spent a few months with multiple cleanings in between range visits. My sense is it was a combination of the gun and the mags.

90 Posts
Let the mags sit loaded for a week.
Seems to do the trick.
Lube it up and got to town.
Just put the first 100rnds through mine this morning.
Tried 10 different mags, 10rnds each.
Heard all the horror stories and was ready for all of them to happen as soon as I pulled the trigger.
Not one single hiccup.
Winchester white box 115grn.

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