My New Sig MPX Pistol

[mdrums]

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 perfectly...so 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 sights...spot 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.

[Ohsheepdog01]

Leave your mags fully loaded for a week before firing and you shouldn't have a problem. Mine are perfect and I'm running Gen 1 mags in a Gen 2 gun.

[CharlieDeltaJuliet]

Congrats on the MPX. I own a gen 2 with the SB Tactical Collapsible Brace and love it. It is one of my favorite guns to shoot. Ohsheepdog01 is absolutely right! I left my magazines (both gen 1 & gen 2) loaded over the winter until I got it out to shoot. It ran like a champ, but I knew that the lancer mags were tight before buying. To answer your question, since the letter of clarity, it is no longer redesigning a firearm to shoulder the brace. So it isn't "making an SBR". Keep Calm and Shoulder On!

[mdrums]

Thanks guys...I had posted on the Sig MPX Facebook page too and they said the same thing about keeping the mags loaded when new. Also suggested was to get a long wooden pole...I can use a drumstick...and work the followers up and down 20 or so times.

Yeah once the gun got running good....I shot it really well....the target post was at 25 years and I was standing and shooting. I'm not great shot either...only been shooting since 2012...but having a lot of fun shooting various guns and taking some courses.

[CharlieDeltaJuliet]

Well you made a great choice. My MPX is one of guns I would hate to imagine getting rid of. Enjoy it!

[GJM]

Based on my sample, along those with other USPSA PCC competitors I shoot with, the MPX seems to be running 50/50 as to whether they need a break in with full power ammo. One of mine did, and another did not. My buddy was 1/2. also, a significant percentage require a trip back to Sig for various out of the box infirmities. Also, look out for small parts, as both my competition MPX 16 inch carbines broke a firing pin spring at 2,000-3,000 rounds.

Separate issue, is full magazines and being able to strip a round manually, when new and fully loaded. This improves with time if you leave the magazines fully loaded.

[mx5rcr]

I had similar issues with mine. I ended up sending it back to Sig for repair. Turns out that the extractor o ring apparently fell out during cleaning and i didn't notice. Check your o ring.
Flawless ever since.

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[VARIABLE9]

Is that Fiocchi any good? I haven't shot it in over a decade because (at least in my pistols) it seemed to be lower quality and just didn't shoot well.

[mdrums]

Is that Fiocchi any good? I haven't shot it in over a decade because (at least in my pistols) it seemed to be lower quality and just didn't shoot well.

It's ok...seemed accurate for me. I had 50 rounds of Blazer Brass (cci speer) that worked good to. I have more Fiocchi to use up though. After that I have some Lawman Speer and American Eagle.

I was just on SGammo.com looking to order a few thousand more 9mm...so much to choose from!....what's good clean powerful accurate 9mm around the .20 to .25 cent a round range ammo?