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Sig MPX gas port


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The MPX is a gas system it needs gas pressure  and dwell time to function. For a Gen 2 gun you just need to pick your powders from the correct burn rate category  (N340, HS6, WSF) . Don't try to use a small charge of fast powder like in a production minor pistol it will not generate  either gas pressure  or dwell time in to the operating system.. 

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working on this as well ... got some AutoComp from a friend and will be working up some loads with 124 Xtremes & maybe 115s ...

 

I've done a few 124 Extremes with WST and it felt soft but have not run enough to determine reliability yet ...

 

I've been doing some more reading and I got the impression that the gas port issue was more with the carbines than the pistols but I don't know how reliable that info is ... don't know if there is any difference between the pistol & carbine versions WRT the gas port system to lend credibility to this ...

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Hello: So how much are they opening up the gas port? 0.005-0.010? If you guys are going the slow powder route you are likely to see a lot of unburned powder at low powder charges to get low power factor loads. HS-6 is pretty dirty when not loaded up to major PF. Auto Comp will burn cleaner down there. I think the Tite Group- WST would be the range I would look at for a 16" barrel. Thanks, Eric

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My understanding is that the gas port is .005 smaller on the Gen 2 and folks were wanting the port to be back the Gen 1 size.   My barrel is only 8".  Not really sure what people are considering low PF loads for the MPX either?  Never used AutoComp before but got enough to make 50 rds or so ... I'd be just s happy to stay with WST.  Been using it for years and love it.  The very few rds I put through my MPX with WST felt nice and I have a ton of it..

Edited by Nimitz
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That MPX is all screwy. 4/5 of our groups MPXs have had issues. Gen 1 needs Gen 1 mags. Gen 2 needs Gen 2 mags. You have to use this ammo. Whatever the case is. Anyways we just sent 3 off the some sig guru guy on another forum who opens the Gen 2 ports to a larger diameter and do something else so hopefully they come back with 100% reliability now.

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Interesting factoid from a day with the chrono and different powders after 2011BLDR let me try some of his rounds.  I have a Gen II with the stock .045 gas port.  Using 125 SNS projectiles  I worked with my 9mm pistol powder of choice E3.  This is a fastish powder which seems to also be the correct answer for blowback carbines.  In order to get the bolt to lock back reliably I needed to run 152.3 PF.  Granted, it still had a lighter recoil impulse than my buddies' blowback guns and the dot didn't bounce excessively but not an ideal load to me.  

 

Next i brought out some N330 I had in the closet which is a mid to slow range powder.  With only that change the bolt would lock back at 113.8 PF and might have gone lower but that was the lightest charge I had.  

 

Long story short:  Your 16" piston operated PCC is not your 5" pistol.  It appears to need a different load if you are going to look for optimal gamer loads.  :-)

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12 minutes ago, Neomet said:

Interesting factoid from a day with the chrono and different powders after 2011BLDR let me try some of his rounds.  I have a Gen II with the stock .045 gas port.  Using 125 SNS projectiles  I worked with my 9mm pistol powder of choice E3.  This is a fastish powder which seems to also be the correct answer for blowback carbines.  In order to get the bolt to lock back reliably I needed to run 152.3 PF.  Granted, it still had a lighter recoil impulse than my buddies' blowback guns and the dot didn't bounce excessively but not an ideal load to me.  

 

Next i brought out some N330 I had in the closet which is a mid to slow range powder.  With only that change the bolt would lock back at 113.8 PF and might have gone lower but that was the lightest charge I had.  

 

Long story short:  Your 16" piston operated PCC is not your 5" pistol.  It appears to need a different load if you are going to look for optimal gamer loads.  :-)

Hello: The same holds true for blowback AR 9mm rifles. Tune the load to the rifle just like you would for your open pistol loads. Isn't E3 a fast powder for sporting clays? Thanks, Eric

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Rick: I think they use E3 for 28 gauge sporting clays loads going 1300fps. Maybe try some slower burning powders and see how that goes. I am using WST in my AR 9mm right now and like it. Tite Group works well, I am also going to try some HP-38 / 231 as well. I have some left over powders that I want to try in 9mm rifle loads to see how I like each of them. As you know you can usually find a sweet spot in the burn chart that works for your application. Kinda like open major 9mm powders. This is an interesting thread about the Sig and what it likes. Thanks, Eric

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Eric, I really like the N330 loads at 130PF.  Only have @ 4lbs of it left though so will be looking for something equivalent.  I have Silhouette which is close.  Also have HS6 which is in the ballpark but at the really low charge weight needed I imagine it will be absolutely filthy to shoot.    

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Hello: The thing with Silhouette when down loaded it leaves some oatmeal looking stuff around. It is also is reverse temp sensitive. I may try some Auto Comp at minor loads to see how clean it burns. You Sig guys have a lot more to deal with than the AR 9mm guys do. If I get a chance hopefully I can shoot a Sig that is setup for PCC someday. Great that we are all sharing info here! Thanks, Eric

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Now Eric, if you still lived in NM you could come down for A2 and shoot mine!  ;-)  You hit on a good point with the powders.  In order to get down to 130 with a lot of them is we have to get down to sub-optimal charge weights.  Results can be a filthy gun, downgraded accuracy, or both.  

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I am happy to duplicate a factory NATO/ EURO spec load..Gives me the same feel and I have the option of using factory for big matches. additionally from whare I buy my factory 9mm it is $40 more per 1k than reloading, if I need the brass... I can't justify my time to buy once fired and load it when I need a brass restocking..

 

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On ‎2‎/‎1‎/‎2017 at 0:00 PM, Neomet said:

Eric, I really like the N330 loads at 130PF.  Only have @ 4lbs of it left though so will be looking for something equivalent.  I have Silhouette which is close.  Also have HS6 which is in the ballpark but at the really low charge weight needed I imagine it will be absolutely filthy to shoot.    

 

 

What is your ballpark powder charge with N330?

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I have a Gen 2 model. Would not run with my competition pistol loads using Titegroup or N320. I had to add an extra four tenths of a grain to make it run.  Nothing wrong with that route, but I prefer to keep things simple - one load for all my guns. So I did send mine off to Taylor to have the gas port opened to Gen 1 size. Got it back about a week ago, so far, it's having no trouble running the same load I use for production and SS minor.

 

 

 

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I have a gen 2 Carbine that runs my 147gn, 3.1gn of Titegroup 3Gun 9mm load (127pf in my limited gun). OAL on it is 1.135".  It gets so dirty though that the piston rings caked up solid at the 1k rounds range. We have that Safariland Expedition Multigun match coming up in Vegas, and there is word of targets out to 75-100 yards, so i wanted to develop a 115gn load for the gun that shot flatter. I was thinking of trying CFE Pistol. What do you guys think about all this?

 

Edited by Snopczynski
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