Mpx, post 700 round mark, looking for handload info that works please

[Venti30]

Just picked up a sig mpx, 8” barrel pistol that I’ll SBR after my trust runs its course and as many have reported, wouldn’t run medium book loads. Had tried running 115 and 124 grain over 4.5 grains of hp38 (Hodgdon range is 4.3 to 4.8), but no go, wouldn’t cycle, fte, ftf. Had to run about 300 factory rounds through it to get it loosened up first. 

After the 30p rounds of factory blazer 115 Grn, (what my home range had on hand) it would run 115 grain over 4.8 grains of hp38 at 1.100 coal hand loads, 99% of the time. 

I brought it home after a blistering range run of 500 rounds of the 115 plated lead round nose /4,8grn/1.100 handloads and was amazed at how dirty the gun was, particularly around the gas valve and tappet. The tapped and valve were stuck nearly solid, carbon seemingly permanently infused to the parts. 

Upon later reading, seems that some advise against plated bullets in the mpx, so my question to my esteemed associates is, given the mpx platform mentioned, does anyone have successful post 700 round count handload recipe for an mpx that they’d like to share?

Many thanks in advance,
JR

[Hi-Power Jack]

I'd start with your usual load, but use FMJ's instead of plated bullets - see if that helps   

[RH45]

As with my open guns, I don't want to run fmj in my MPXs because fmjs have exposed lead at the rear of the bullet, and, as you found out, cleaning the gas valve is a p.i.t.a.

I also want to run the cleanest powder, for the same reason, so I chose VV320.

I didn't like the feel of heavy bullets.

Even though they aren't the most accurate bullet, I went with Extreme 115 hollow points. They group about an inch at 25 yards, and upper A zone hits offhand at that distance, aren't a problem.

My USPSA load is 4.2 grains of 320, but, I have the longer barrel. My IDPA load is 4.5 grains of 320, that chronos out of my 5' M&P at 131pf, and 141pf out of my MPX.I can barely tell the difference between the two loads, regarding recoil & dot movement.

I'm guessing that, with an 8" barrel, you would need about 4.3 grains of VV320 to make pf, but, I prefer a little cushion, so I would probably go with 4.4. 

A friend of mine, did a torture test on his, with no cleaning, and made it to about 5k before it started acting up.

I've been cleaning both of mine at about 500 rounds, and I think that's long enough because I have to use a brass punch to tap the valve apart.

[Bummy425]

I'm running same barrel length...115 great coated in blue bullets under 4.5 great win 231 ( same as he 38) no issues. Will also run my USPSA production loads of 147 FP blue bullets coated under 3.5 great of win 231, but don't like the way they feel.

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