MPX - Gen 1 Mag in Gen 2 Gun FTF Reloads

[TightLines]

Have done some research without much luck.

 

When I first received my Gen 2 MPX I quickly found my light 9mm loads (4gr RD, 115 Xtreme RN @ 1.135 OAL) would not cycle or reliably feed with Gen 1 or 2 mags but it gobbled up any and all factory loads.  Second set of loads I increased charge until the gun would properly cycle but quickly found I was having severe feeding issues.  Increased OAL to 1.160".

 

Current load of 5.5gr of Unique, 115gr Xtreme plated @ 1.160" runs like a top in my single Gen 2 mag.  Put the same load in my Gen 1 mags and it's constant FTF all over again.  The rounds all jam in the same manner (picture below).  

 

The only other exterior spec that differs from my loads to factory is the amount of crimp and I've got my back against a wall (.377) here since I like the economics of plated bullets.  All rounds pass the plunk test.

 

Any insight here?  Have a handful of Gen 1 mags I picked up at a decent price and would love to get these working.

 

TLDR:

Gen 2 MPX cycles reloads and factory ammo perfectly out of Gen 2 mags.

Gun eats factory ammo with Gen 1 mags but severe FTF with reloads.  Rounds at 1.160" and .377" crimp.

 

 

 

 

[TightLines]

A little more detail.

Looks like the nose of the rounds are actually hitting the top of the barrel throat. I'm guessing this is also the cause (could be the effect) of the round not seating properly against the bolt.

See additional photos below (one shot from inside the mag well).

The rounds feed much better when hand cycled than when fired.

Only steps I have before swearing off the Gen 1 mags for reloads (all I shoot):

Try shortening up the OAL to 1.050 and/or try reducing crimp a hair to .376 or so.

 

 

Edited April 9, 2017 by TightLines

[IntenseImage]

How many rounds have you put on the Gen1 mags?

Sent from my SM-N920V using Tapatalk

[TightLines]

Likely no more than 30-60 through each of the factory mags.

 

Instead of trying to trouble shoot with a bunch of factory ammo.  Maybe I'll try cycling the magazines with a dowel rod.

 

Would the magazines being a bit oversprung result in these types of failures?

[SergioSF]

I've been told that the tapered feed lips of the Gen1 mags, combined with a too-short OAL is part of the issue. The tapered lips allow the round to tilt up too soon, before the tip of the bullet can get into the chamber. 

 

However, if I run factory 115gr ammo thru my Gen1 mags, they will function just fine. I think the higher velocity is able to overcome the short feed lips.

If I use my soft 147gr loads, they will hang up and doublefeed and FTE. 

 

So if I want to run my soft loads, I have to use my Gen2 mags. 

[TightLines]

Interesting and thanks for the input.

 

Perhaps I'll try a heavier load WITH the longer OAL.  As it is, I can't really go longer on the OAL.