NOSHMJ

I had a very similar issue. New mag and problem solved. I was using a glock mag with MBX extension. I change to new mags and springs every season now because I learned the hard way. Take a new mag spring and compare it to your old one and I bet you will see a difference in length from compression.

I use it for my Limcats. KKM Tungsten sleeved.

nice to hear

I use 7.4 grn under a 124grn for 9mm major

I use the Lee Universal decapping die, and have busted multiple pins with that. I found a set of aftermarket replacement pins on Ebay and have had very good success with those. With that said, I also have a separate tool head I decap, and resize. Then when its time to load, I swap tool heads, and I have another decapping die in station 1 to make sure flash hole is clean, then load normal from there.

I ran 147 Blues under 6.2grn of PowerPistol. It worked well enough for what I wanted out of it. Its not the 124s you are looking to use, but may be a starting point.

Try a SB resizing die.

I have had very good success with Hornady 140 ELD match bullets. H4350 is the go to, but also have had good results with Varget. I have the Redding dies, and have gone to 650yds with ease.

PowerPistol works really well foe .380, and 9mm. A little dirty, but never had an issue with it.

I use Slip 2000 up here in NH all year, granted there isnt any matches after Dec, but Jan and Feb practice, the gun runs perfect.

I find the MPX, well at least mine, loves the 150+ power factor.

I have the DVC steel, and I run minor power bullets with zero muzzle flip all day long. As far as the extraction issues, I just tuned my normal exractor, and its about 99% reliable. Id say make a few different loads with different bullet weights/powder combos to see what works before you change barrels. You may also try swapping recoil springs to see if any improvement comes from it.

I ordered from Gallant 9/18. I finally got a hold of someone who told me an additional 3-4 weeks from 2 days ago.

I guess it was worth asking...

Ive ran thousands of coated bullets thru my MPX, without a single hiccup, or failure. I run 147 Blues under 4.0 grn of power pistol. I clean the gun after about 1000 rds. Scrub the piston and piston chamber clean with a brass brush. I run my bolt sloppy wet against peoples recommendations, but it has yet to fail. I do carry spare extractor springs and the little rubber washers with me because they are going to fail. The thing feels like a shooting a rimfire.