MPX Bulging Brass

[GregJ]

Burned up some light reload rejects this weekend in my Sig MPX Carbine and noticed a lot of bulged brass, very similar to the infamous Glock bulge. First I had noticed this. I think because the loads were light. Anyone run into this?

Edited February 6, 2017 by GregJ

[GregJ]

 

I've put nearly 3k rounds through it and first time I have seen this. Definately from the chamber. 

Edited February 6, 2017 by GregJ

[CZ85Combat]

were you bump firing it?

[GregJ]

7 hours ago, CZ85Combat said:

were you bump firing it?

 

LOL  Nope.

 

To clarify, I was burning up rounds that had been pulled apart, as they were loaded when I first got my 1050 and was trying to get it sorted out. All swagged/over crimmped bullets were culled out, as was anything else that had an issue, The rounds were loaded with 3.6gr of E3, which shoots well out of my 5" 1911 SS, about 131PF.

 

Thinking about it more, some of the rounds felt light - not sure why.  Also some of the pulls were 115s plated, most were 124gr jacketed. I did have one that the case let loose at the bulge, which was interesting.

 

 

 

[Steve RA]

Might fire a factory round in it and see what it looks like.

[GregJ]

1 hour ago, Steve RA said:

Might fire a factory round in it and see what it looks like.

 

I was planning on doing that this weekend, as well as some of my regular loads.  tks

[GregJ]

I am beginning to think the E3 is just too fast for the MPX. This would explain the bulge.   I will try chronoing a few rounds and see.  

[Aircooled6racer]

Hello: Could the bullet be hitting the lands in the barrel causing the pressure to go up ? Maybe use the barrel as a case gauge and see. Thanks, Eric

[GregJ]

1 hour ago, Aircooled6racer said:

Hello: Could the bullet be hitting the lands in the barrel causing the pressure to go up ? Maybe use the barrel as a case gauge and see. Thanks, Eric

 

Absolutely possible.  Still need to check this just havent gotten to it, though I was loading the rounds in question at 1.100/.3775.  tks

[GregJ]

I chrono'ed a few rounds this evening, and believe either some of the reloads in question were a little long (hitting the lands causing a pressure spike), or loaded heavy.  

 

String below is 6 rounds of Freedom Munitions New 115gr RN. (Avg and PF calculated by my CED). Shot these for comparison purposes.

1206

1212

1249

1178

1216

1228

Avg= 1214

PF= 139.7

NOTE: There were very slight marks from the unsupported area of the chamber on a couple pieces of brass. You would miss it if you were not looking for it.  The CCI primers did have a black dot from the firing pin. looked like a hole but wasnt - very strange.

 

String below is 6 rounds 124gr Zero, 1.100/.3775, 3.6gr E3 (Avg and PF calculated by my CED)

1060

1065

1095

1090

1078

1097

Avg=1080

PF=134.0

NOTE: 2 pieces had a slightly more visible impression from the unsupported area of the chamber, but no "bulge". Rest looked fine.

 

Looks like 3.4-3.5gr of E3 might be the sweet spot as far as PF goes. Or maybe load a little shorter.  More testing/chrono work, but I think I have the answers now.  

 

[Steve RA]

Usually if you get a bulge it means that there is an unsupported area under the case where the bulge occurs.  Otherwise there would be no place for the bulge to develop!

[GregJ]

2 hours ago, Steve RA said:

Usually if you get a bulge it means that there is an unsupported area under the case where the bulge occurs.  Otherwise there would be no place for the bulge to develop!

 

I understand that. I guess I was under the impression the MPX did not have this issue. Partly because I just now noticed it, after putting about 3k rounds thru it. But it indeed has an unsupported chamber. So I guess some bulging is normal with this gun. 

[GregJ]

And the hits just keep coming. Appears The Freedom ammo I chrono'd this aft has pierced primers. Looked at the firing pin. Dont have a new one to compare too, but will order a couple. 

[StealthyBlagga]

Will SIG even sell you a replacement firing pin? The lack of spare parts availability is one of the reasons I have been reluctant to consider this platform.

Edited February 7, 2017 by StealthyBlagga

[Neomet]

Richard...... no.  I have tried twice to get a spare but was refused both times.  I am much less than pleased by this.  

[Aircooled6racer]

14 minutes ago, Neomet said:

Richard...... no.  I have tried twice to get a spare but was refused both times.  I am much less than pleased by this.  

Hello: Well that kinda sucks that you can't get a spare part that may break and can be changed out at the range. Looks like an opening for aftermarket guys to start making spares for the Sig MPX. Thanks, Eric

[Neomet]

Yeah, I made that very point and explained that if a part ever fails it is on stage one of a match you traveled across the country and sunk $3K into.  They were unimpressed.  

 

[GregJ]

A knowledgable friend suggested the bulges were due to firing out of battery.  I will call Sig this am and see what they say about this and the firing pin.

 

EDIT: 

Called Sig CS, they are sending an upgraded BCG which includes FP and FP spring.  Seems they dropped the FP spring with the Gen2, and are adding it back. Interesting.

 

He didnt have much input on the case bulge, other than stay away from Freedom ammo.   Of course he also suggested to stay with factory ammo. We'll see how the upgraded BCG helps with the bulging. 

Edited February 7, 2017 by GregJ

[Tom Freeman]

7 hours ago, GregJ said:

other than stay away from Freedom ammo.   

 

 

Yup.

[Aircooled6racer]

17 minutes ago, Tom Freeman said:

 

 

Yup.

Hello: These are some reloads that did not go well. These are not factory loaded but shows you what can happen with these two piece cases. Not mine but cool to look at. Thanks, Eric

[IntenseImage]

That FP spring is to help w over penetration of the FP so should at least solve that issue for you

[1911luvr]

Hello: These are some reloads that did not go well. These are not factory loaded but shows you what can happen with these two piece cases. Not mine but cool to look at. Thanks, Eric

 

 

I've seen at least 3 of these, and each one was from a piece of brass with a line around the middle kind of like a cannelure. Each piece separated at the line.

 

 

Sent from my iPhone using Tapatalk

[GregJ]

If anyone is interested, here is a pic of the original BCG and the upgrade Sig sent. The new FP is a tad shorter. The original was 2.76 and the new us 2.65 - IIRC. I will see how it works tomorrow.