MPX vs CZ

[Honeybooboo]

I know. This has been talked about before. I want to get a PCC. My brain keeps telling me to get an MPX because because of it's advantages, primarily the fact that it shoots real soft for fast splits. 

For some reason i really want the CZ. I like its light weight and it just feels good shouldering. 

Tafan Butler says the MPX is a real advantage over everything out there. Is it really the case? Are you limiting yourself with a CZ? 

[surgdog]

I have both that I have tried to set up for PCC competition. Both are pistols that I SBR'ed. I did make some modifications to the CZ with the HBI trigger spring kit and changed the right sided safety.

The CZ has worked without a problem and will shoot any ammo fed to it. It is very accurate. Works with my reloads very well.

I love the looks of the MPX but I have problems with FTE with my reloads (147 gr xtreme RN over 3.3 gr Titegroup). It fires commercial ammo without fail. Others have pointed out that the Gen 2 MPX which I have is "undergassed" but improves with a break in period of a few hundred rounds of commercial ammo and mine has gotten better but not 100% yet. I'm considering sending it to have the gas port enlarged which seems to correct the problem. You would think that a gun that costs significantly more than the CZ would work with all ammo.

If I were to get only one at this point I would go with the CZ for cost, reliability and easy modification if felt necessary by you.

Just my 2 cents. I'm sure others will have different opinions.

[2011BLDR]

The MPX is a gas operated system and has different operating requirements than a recoil or blowback  system. Your load is the issue with the MPX. it is a gas system it needs gas pressure  and dwell time to function, a small charge of fast powder is not generating either gas pressure  or dwell time in to the operating system.  A slower burn rate powder would help (N340, HS6, WSF). 

[surgdog]

6 minutes ago, 2011BLDR said:

The MPX is a gas operated system and has different operating requirements than a recoil or blowback  system. Your load is the issue with the MPX. it is a gas system it needs gas pressure  and dwell time to function, a small charge of fast powder is not generating either gas pressure  or dwell time in to the operating system.  A slower burn rate powder would help (N340, HS6, WSF). 

I certainly agree with your statement but I have used my recipe for my handguns and don't want to change or have a different load for just one gun. If I can accomplish that by opening the port a bit it would be worth it.

As far as the OP original question about an opinion between the two its just my personal experience that as far as obtaining one of the two and going to shoot the CZ is a more competition ready platform IMO. I love the MPX. It is cool and a blast to shoot. It's just taking more tweaking than the CZ and for almost twice the money I would think it would shoot anything fed to it. But as you rightly point out it is a different operating system and as also pointed out in a different thread on here somewhere Sig probably didn't design it for competition. Once I get it going I can't wait to shoot it in completion with my handloads.

[2011BLDR]

i hear 

16 minutes ago, surgdog said:

I certainly agree with your statement but I have used my recipe for my handguns and don't want to change or have a different load for just one gun. If I can accomplish that by opening the port a bit it would be worth it.

As far as the OP original question about an opinion between the two its just my personal experience that as far as obtaining one of the two and going to shoot the CZ is a more competition ready platform IMO. I love the MPX. It is cool and a blast to shoot. It's just taking more tweaking than the CZ and for almost twice the money I would think it would shoot anything fed to it. But as you rightly point out it is a different operating system and as also pointed out in a different thread on here somewhere Sig probably didn't design it for competition. Once I get it going I can't wait to shoot it in completion with my handloads.

I hear you, I just think of the MPX as the PCC equivalent of an open or limited gun that you tune the loads to exploit the advantages the system has to offer.  I would never consider running a blowback gun in PCC it is just to slow of a cycle time compared to an AR, open or limited gun for me.

As a side note I saw a guy have a out of battery detonation with a CZ a few weeks ago in a match his trigger finger out ran the operating system.

[Aircooled6racer]

2 minutes ago, 2011BLDR said:

i hear 

I hear you, I just think of the MPX as the PCC equivalent of an open or limited gun that you tune the loads to exploit the advantages the system has to offer.  I would never consider running a blowback gun in PCC it is just to slow of a cycle time compared to an AR, open or limited gun for me.

As a side note I saw a guy have a out of battery detonation with a CZ a few weeks ago in a match his trigger finger out ran the operating system.

Hello: A blowback AR 9mm is too slow of cycle time? I can do 0.14-0.18 splits pretty easily with mine at 10 yard "A" zone head shots. Granted I have spent some time tuning everything to work as a total package. I think any of the platforms can be made to work well with some tuning and time behind it. Total cost of the rifle has to come into play as well. I think there will be more options as time goes on and people play with these different platforms. As I have said before see if you can shoot one and see what you like best. Thanks, Eric

[2011BLDR]

Key words being " for me" . I get .08 -.10  splits pretty easily with an AR or the MPX and as fast as it sounding like a Double fire on a close wide open target. 

I run my 9mm 3gun load from my 5" and 6" 2011's 125gr MG JHP 5.6gr N340 1290 fps in the MPX , 1220 in the 6"  and 1190 fps in the 5".  My point being a locked breach gas operated system has difrent ammo requirements than a blowback unlocked system. I agree you can play around with weight, springs and loads to optimize that blowback system. However that also narrows the operating band on it also, would you want to put a NATO spec or Open 9 round in to that blowback system optimized for a Production minor load with a small charge of fast powder? I wouldn't.

For me one of the selling points of PCC and my MPX is I don't have to fly with reloads. I can buy NATO / Euro spec 9mm on site at a flyaway match that preform like my reloads. 

 

 

[Neomet]

Kevin, i am still working a load up for my MPX and while I get the logic of a slower burning powder your load is just over 161 PF which raises a couple of follow up questions.  Do you just prefer to shoot at that high a PF or is that as low as you can go reliably?  I get reliable function at @ 150PF with E3 and it is a weeeeeeee bit faster than 340.  (still feels softer than 130 PF in a blowback).  I guess the two salient questions are A Can you get down to 130PF with slower powder and B Is 130PF even the right goal to pursue?

[rowdyb]

I sold my CZ and bought another 9mm AR. Why?

• the gun and mags would not function reliably with my current pistol load. i have too many match videos of me clearing multiple fte's on stages and i refuse to make a carbine load different than my pistol load.
• there is no aftermarket to tune the "bcg" or its associated spring the way you can on a 9mm AR.
• the fore end was uncomfortable for my chosen grip method. no one makes a smaller or more rounded profile aftermarket replacement.

The gun had a lot of positives that's for sure. But mine was not a runner and it didn't give me the feeling in hand while operating it to make it a good game gun for me.

 

It sounds crazy to say it, but my 9mm AR is more reliable and fits me better. But what the CZ has going for it in my experience is:

• once you can access the trigger pack, dang stupid welded bolt, doing a polish and spring install is easy and yields a vastly better trigger than stock for very low dollars.
• mags are super cheap. and easy to make drop free all the time with a little sanding.
• controls are in a good place. operating the bolt, the safety, the mag release all of that stuff is in a good spot and easy to do quickly.
• very good cheek weld. good stock
• light feeling
• polymer lower makes beveling a magwell very easy to do
• lower entry cost
• easy to sbr

But for me, all those didn't outweigh a gun that wouldn't run my pistol ammo 99% of the time with no adjustment.

[2011BLDR]

10 hours ago, Neomet said:

Kevin, i am still working a load up for my MPX and while I get the logic of a slower burning powder your load is just over 161 PF which raises a couple of follow up questions.  Do you just prefer to shoot at that high a PF or is that as low as you can go reliably?  I get reliable function at @ 150PF with E3 and it is a weeeeeeee bit faster than 340.  (still feels softer than 130 PF in a blowback).  I guess the two salient questions are A Can you get down to 130PF with slower powder and B Is 130PF even the right goal to pursue?

 

I found that in my 16" gun my 125gr Montana Gould JHP @ 1290fps (5.6gr N340) 161 PF  was softer with less sight movement than the same bullet @ 1160 fps (5.4gr 3N37) 145 PF. The 3N37 load was initially 1090 fps 136 PF and not  reliable brass fell out the ejection port at your feet and had massive sight movement in recoil and counter recoil.

IMO a 130 PF goal is not where I want to be, my development goals were:

• Reliablity
• Fast cycling withe the least amount of  sight movement
• Ability to match an available commercial spec load for: 

1. Flyaway matches
2. Brass replenishment
3. Cycle time close to an AR or an Open pistol 

 Speer 124gr TMJ or Geco  European spec 124gr  both hit the 1280-1325fps range and meet my goals on 1&2.

 

I did arrive at  this load vary easy I had about 1K of the 3N37 load  that was run by a friend when my reloading set up was torn down for construction of my new reloading space,I had to shorten the OAL and tighten up the crimp for the MPX and that put it up to 145PF. The other load of 5.6gr N340 was the same charge I used in my .40 6" limited gun.  When I looked it up an it was within the range for 9MM so I  just ran with it, thought if it worked it was one less step converting that press from 9mm to .40 or back.

If the 150PF load meets your goals it should be good to go. If you are a @ Rio this Sunday I will give you a handful of the 161PF loads.

Edited January 27, 2017 by 2011BLDR

[Neomet]

Thanks Kevin.  Yep I will be at Rio.  5 stages of steel is impossible to say no to.  :-)  I am tending to agree with you that the MPX has less dot movement at higher PF.  Not sure why because we aren't running comps but it is what it is.  Plus I am really tired of clearing the jams I started getting when I dropped the PF down from my higher "break in" load.  

[bmiller]

Those of you running the MPX, does your gun blow powder residue back into the action with the slower powders. I tried auto comp and hs6 in my blowback gun, it was a filthy mess.  My blow back is pretty filthy even with faster powders. I am sure it is the nature of the beast.  The mpx cleaner in general?

[2011BLDR]

1 minute ago, Neomet said:

Thanks Kevin.  Yep I will be at Rio.  5 stages of steel is impossible to say no to.  :-)  I am tending to agree with you that the MPX has less dot movement at higher PF.  Not sure why because we aren't running comps but it is what it is.  Plus I am really tired of clearing the jams I started getting when I dropped the PF down from my higher "break in" load.  

 It is down to cycle length, cycle time, port presser and dwell time. If you are short stroking the system you will have the carrier mass in counter recoil effecting the gun when it closes,  because it did not dissipate the correct amount of energy in to:

• full spring compression (cycle length)
• the receiver buffer stop (cycle time)

Being similar to an AR  system with a brass deflector if your brass is not going to 2 o'clock you are short stroking.