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Posted: 8/27/2016 8:04:43 PM EDT
I picked up a Gen 2 MPX yesterday.  Having not shot a single round, it's completely taken down and set up to receive a few mods.  One being the barrel chopped to 4.5".

Having the 4.5" barrel and the stock length hand guard would mean I shoot suppressed all the time.  Are any of you doing this?

Do you miss the versatility of being able to shoot non-suppressed if the spirit moves you?

I'm not too keen on modding the stock hand guard just yet.  That said, should I hold off on the barrel until the "K" hand guard is available?
Link Posted: 8/27/2016 11:16:35 PM EDT
[#1]
Remember most people are reporting A LOT of GTF when shooting the MPX suppressed.  I haven't fired my with the suppressor on yet, so I don't know if this in fact the case of not.
Link Posted: 8/28/2016 12:06:14 AM EDT
[#2]
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Quoted:
Remember most people are reporting A LOT of GTF when shooting the MPX suppressed.  I haven't fired my with the suppressor on yet, so I don't know if this in fact the case of not.
View Quote


Depends on the suppressor, from the reports I've seen.
Link Posted: 8/28/2016 2:05:17 AM EDT
[#3]
I'll be running a Griffin Rev 9...
Link Posted: 8/28/2016 11:30:09 AM EDT
[#4]
I've had a 4.5" for a few months with the K handguard. I only shoot it with my octane 9 while I'm waiting for my omega 9k to get out of jail and that will live on the mpx.
Link Posted: 8/28/2016 5:12:57 PM EDT
[#5]
I have a AAC eco9 that lives on mine full time. No GTF for me. I've had a k length hand guard on order for a year now not sure I'll ever get one.
Link Posted: 8/28/2016 5:58:40 PM EDT
[#6]
Few hundred rounds through my MPX w/AAC TiRant, zero issues with gas in the face
Link Posted: 8/28/2016 7:45:16 PM EDT
[#7]
I chopped my hand-guard myself and when i'm at the indoor range don't shoot it with the can on because why bother when others are shooting.

Also, it can get a little gassy while doing mag dumps at the indoor range because i'm between lane dividers and no wind but that is it.

At the end of the day, the gas to face issue is a personal one for each shooter, some people are more sensitive to minor irritations then others.


Link Posted: 8/28/2016 8:09:01 PM EDT
[#8]
Is morgan at class3 still the "go to" guy for the cut and thread?
Link Posted: 8/28/2016 9:18:19 PM EDT
[#9]
Quoted:
Is morgan at class3 still the "go to" guy for the cut and thread?
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Yes! Did mine!
Link Posted: 8/29/2016 12:21:06 AM EDT
[#10]
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Quoted:



Yes! Did mine!
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Is morgan at class3 still the "go to" guy for the cut and thread?



Yes! Did mine!

Awesome work by him.
Link Posted: 8/29/2016 1:54:52 AM EDT
[#11]
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Quoted:
Few hundred rounds through my MPX w/AAC TiRant, zero issues with gas in the face
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TiRant 9 or .45?
Link Posted: 8/29/2016 10:47:39 AM EDT
[#12]
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Quoted:


TiRant 9 or .45?
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Few hundred rounds through my MPX w/AAC TiRant, zero issues with gas in the face


TiRant 9 or .45?



I have the 9, friend has the 45, and neither of us get GTF.  However, our barrels aren't cut if that matters.


Link Posted: 8/30/2016 12:47:05 AM EDT
[#13]
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Quoted:
I've had a 4.5" for a few months with the K handguard. I only shoot it with my octane 9 while I'm waiting for my omega 9k to get out of jail and that will live on the mpx.
View Quote


Howd you get the K handguard?!
Link Posted: 8/30/2016 11:47:01 AM EDT
[#14]
Well. Round count... Idk between 13-19k+ maybe getting closer to 20 Kinda stopped counting. Anyways after the chop I never once wanted to shoot this thing unsupressed. If I did I would buy another one. Besides having to replace all of the springs I have no regrets with the gun being cut down. Keeps the center of mass closer and the cut down handgaurd looks goofy with the pistol brace so I just kept full length. I just wish I could water block cool this thing... Or speed loaders for the 12 magazines...
Link Posted: 8/30/2016 3:43:00 PM EDT
[#15]
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Well. Round count... Idk between 13-19k+ maybe getting closer to 20 Kinda stopped counting. Anyways after the chop I never once wanted to shoot this thing unsupressed. If I did I would buy another one. Besides having to replace all of the springs I have no regrets with the gun being cut down. Keeps the center of mass closer and the cut down handgaurd looks goofy with the pistol brace so I just kept full length. I just wish I could water block cool this thing... Or speed loaders for the 12 magazines...
View Quote


Can you elaborate about the springs you changed?  It has been my impression that these guns are over gassed, and shortening the barrel reduces the pressure, while a suppressor helps maintain the longer dwell, but this is mostly from listening to other people.  I do know that in the one I tried it would cycle with some of my reloadsthat are so weak they won't eject from a Glock
Link Posted: 8/30/2016 9:35:11 PM EDT
[#16]
I don't have many rds down range since my barrel/rail chop. But I must say I haven't noticed any gas to the face. That's can wet or dry, I'm using a tirant 45s and 4" barrel on a gen 2 gun. I have no regrets. My main reason for rail chop was so I could shoot unsupressed as well.
Link Posted: 8/30/2016 9:39:20 PM EDT
[#17]
How much does just the barrel cut and re-thread cost?
Link Posted: 8/30/2016 9:48:59 PM EDT
[#18]
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How much does just the barrel cut and re-thread cost?
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IM inbound
Link Posted: 8/31/2016 12:09:19 AM EDT
[#19]
I was wondering if you could send me a price also
Link Posted: 9/1/2016 10:15:48 AM EDT
[#20]
Link Posted: 9/1/2016 10:32:53 AM EDT
[#21]
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Quoted:


There's not a lot of blowback at all-  I don't know where all of that talk is coming from.   Below is a select fire 4.5" suppressed (Omega 9K) MPX.   There's an Uzi on there for comparison, and at the end a close up, slow motion of dumping a mag.  

https://youtu.be/fZ_ubnpY8h4

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Quoted:
Quoted:
Remember most people are reporting A LOT of GTF when shooting the MPX suppressed.  I haven't fired my with the suppressor on yet, so I don't know if this in fact the case of not.


There's not a lot of blowback at all-  I don't know where all of that talk is coming from.   Below is a select fire 4.5" suppressed (Omega 9K) MPX.   There's an Uzi on there for comparison, and at the end a close up, slow motion of dumping a mag.  

https://youtu.be/fZ_ubnpY8h4



I don't understand either, it hasn't even registered to me.


Link Posted: 9/1/2016 2:13:00 PM EDT
[#22]
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Quoted:


I don't understand either, it hasn't even registered to me.


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Quoted:
Quoted:
Quoted:
Remember most people are reporting A LOT of GTF when shooting the MPX suppressed.  I haven't fired my with the suppressor on yet, so I don't know if this in fact the case of not.


There's not a lot of blowback at all-  I don't know where all of that talk is coming from.   Below is a select fire 4.5" suppressed (Omega 9K) MPX.   There's an Uzi on there for comparison, and at the end a close up, slow motion of dumping a mag.  

https://youtu.be/fZ_ubnpY8h4



I don't understand either, it hasn't even registered to me.




I think it came from MAC's youtube comparison of the MPX and the Scorpion.  He talks about it quite a bit and I read a lot of people's forum posts mentioning it after that video came out.  I haven't noticed any on mine either though using a Trident 9 and an Octane45.

Curious though, why do you guys chop your handguards with a shorter barrel?  Is it an aesthetics thing?  I think the longer handguards look a lot better personally, but just wondering if there was another reason.
Link Posted: 9/1/2016 2:28:58 PM EDT
[#23]
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Quoted:


I think it came from MAC's youtube comparison of the MPX and the Scorpion.  He talks about it quite a bit and I read a lot of people's forum posts mentioning it after that video came out.  I haven't noticed any on mine either though using a Trident 9 and an Octane45.

Curious though, why do you guys chop your handguards with a shorter barrel?  Is it an aesthetics thing?  I think the longer handguards look a lot better personally, but just wondering if there was another reason.
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Quoted:
Quoted:
Quoted:
Remember most people are reporting A LOT of GTF when shooting the MPX suppressed.  I haven't fired my with the suppressor on yet, so I don't know if this in fact the case of not.


There's not a lot of blowback at all-  I don't know where all of that talk is coming from.   Below is a select fire 4.5" suppressed (Omega 9K) MPX.   There's an Uzi on there for comparison, and at the end a close up, slow motion of dumping a mag.  

https://youtu.be/fZ_ubnpY8h4



I don't understand either, it hasn't even registered to me.




I think it came from MAC's youtube comparison of the MPX and the Scorpion.  He talks about it quite a bit and I read a lot of people's forum posts mentioning it after that video came out.  I haven't noticed any on mine either though using a Trident 9 and an Octane45.

Curious though, why do you guys chop your handguards with a shorter barrel?  Is it an aesthetics thing?  I think the longer handguards look a lot better personally, but just wondering if there was another reason.


Same here, I'm cutting my barrel for my Omega K but I prefer to leave the long handguard.


Link Posted: 9/1/2016 2:35:48 PM EDT
[#24]
So you can also shoot unsuppressed
Link Posted: 9/1/2016 6:06:37 PM EDT
[#25]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


Can you elaborate about the springs you changed?  It has been my impression that these guns are over gassed, and shortening the barrel reduces the pressure, while a suppressor helps maintain the longer dwell, but this is mostly from listening to other people.  I do know that in the one I tried it would cycle with some of my reloadsthat are so weak they won't eject from a Glock
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Quoted:
...


Can you elaborate about the springs you changed?  It has been my impression that these guns are over gassed, and shortening the barrel reduces the pressure, while a suppressor helps maintain the longer dwell, but this is mostly from listening to other people.  I do know that in the one I tried it would cycle with some of my reloadsthat are so weak they won't eject from a Glock


By springs replaced I mean both recoil springs. My firing pin return spring as all of them wore out. Firing pin was about every 6k rounds. Recoil springs were replaced around 12k as they were having a rough time getting the bolt to load rounds. Yes the whole system is excessively gassed.  

But mainly unless your cleaning out the piston often it's relief cable is closed due to a clog of buildup.
Link Posted: 9/2/2016 1:59:45 PM EDT
[#26]
My barrel is on it's way back home!  Thanks Morgan!!



Mags will be delivered next Tuesday.  Fixed barrel end cap for my can is here...  Barrel probably on Wednesday or Thursday...

Looks like I'll spend the weekend barbecue'n and loading 9mm!  
Link Posted: 9/7/2016 10:01:54 PM EDT
[#27]
Quoted:
I've had a 4.5" for a few months with the K handguard. I only shoot it with my octane 9 while I'm waiting for my omega 9k to get out of jail and that will live on the mpx.
View Quote


Did you buy a k handguard or cut yours down?

To the OP I will hopefully get a chance to test out mine this weekend. Barrel cut to 5 inches with a 3 lug threaded over it.





Just got the stamp back. Will be running it with the octane 45 for a while until the octane 9 gets out of atf jail.
Link Posted: 9/7/2016 10:19:40 PM EDT
[#28]
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Quoted:


Did you buy a k handguard or cut yours down?

To the OP I will hopefully get a chance to test out mine this weekend. Barrel cut to 5 inches with a 3 lug threaded over it.

http://imageshack.com/a/img922/3758/g7Xa5b.jpg

http://imageshack.com/a/img923/8452/zQcHbw.jpg

Just got the stamp back. Will be running it with the octane 45 for a while until the octane 9 gets out of atf jail.
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I've had a 4.5" for a few months with the K handguard. I only shoot it with my octane 9 while I'm waiting for my omega 9k to get out of jail and that will live on the mpx.


Did you buy a k handguard or cut yours down?

To the OP I will hopefully get a chance to test out mine this weekend. Barrel cut to 5 inches with a 3 lug threaded over it.

http://imageshack.com/a/img922/3758/g7Xa5b.jpg

http://imageshack.com/a/img923/8452/zQcHbw.jpg

Just got the stamp back. Will be running it with the octane 45 for a while until the octane 9 gets out of atf jail.


Hot damn that looks good.

I still haven't decided on cutting mine yet. It's boxed up to go back to Sig for now though, shattered extraction spring early on and don't know why.



Link Posted: 9/7/2016 10:44:40 PM EDT
[#29]
Those pictures don't give that paint job justice. It looks really good in the light.

Yea I was talking to Mike from TSC Machine a while ago when I had them engrave the gun with the sbr markings. He hadn't seen one of them in person and was really interested in it. I was talking to him about waiting for the sig 4.5 inch barrel and not knowing when they would actually be in stock and he started talking about cutting and threading options. While talking we talked about colors he pulled out a MP5 that he had just done in the burnt bronze for someone. He then started to mention other colors and I stopped him and said how much in that.

When his wife called me to say the work was done she was saying how impressed I was going to be. She was right, it really turned out looking amazing.
Link Posted: 9/9/2016 10:05:04 PM EDT
[#30]
I know this thread's about more extreme barrel chops, but I'm considering sending my SBR for a rethread and a "modest" chop, like only one to two inches.  That'd help reduce the length a little, get my barrel threaded to match my Tirant9, and also might look OK with a 6.5" handgaurd and the oem Sig full-length handgaurd too (with suppressor attached).  Obviously, the 6.5" handgaurd would be used for either suppressed/unsuppressed, and the full length handgaurd would be dedicated to suppressor sessions only.

Kind of a nice compromise for suppressor use, using a 6.5" Lancer CF handgaurd, and getting rid of the metric barrel threads.

One inch, from 8" to 7"...is this a good idea or just a good example of Classs3 pusification on my part? lol

Link Posted: 9/10/2016 10:09:35 AM EDT
[#31]
Mine is at 6", I love it. Have the 10" Lancer handguard on order.
Link Posted: 9/10/2016 10:17:54 AM EDT
[#32]
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Quoted:
Remember most people are reporting A LOT of GTF when shooting the MPX suppressed.  I haven't fired my with the suppressor on yet, so I don't know if this in fact the case of not.
View Quote



Right handed, GTF is minimal (octane 45). My left handed friend got a facefull, however. I figured the charging handle vents to the right side of the receiver or something but haven't really looked into it.
Link Posted: 9/10/2016 6:58:33 PM EDT
[#33]
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Quoted:



Right handed, GTF is minimal (octane 45). My left handed friend got a facefull, however. I figured the charging handle vents to the right side of the receiver or something but haven't really looked into it.
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Quoted:
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Remember most people are reporting A LOT of GTF when shooting the MPX suppressed.  I haven't fired my with the suppressor on yet, so I don't know if this in fact the case of not.



Right handed, GTF is minimal (octane 45). My left handed friend got a facefull, however. I figured the charging handle vents to the right side of the receiver or something but haven't really looked into it.


Yea I took mine out today for testing. I'm a south paw and I was getting gas in the face but it wasn't that bad. I did try it right handed and it was very low, to the point I wouldn't consider it an issue. I brought my 10.5 inch suppressed LMT rifle for comparison and it was far worst. Honestly if sig put a shell deflector on the mpx like an ar has I don't think the gas would have been an issue for a lefty either.

When I did faster firing the gas got noticeable. For normal firing rates though it really isn't an issue on mine which was chopped to 5 inches.

Link Posted: 9/12/2016 11:38:43 AM EDT
[#34]
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I know this thread's about more extreme barrel chops, but I'm considering sending my SBR for a rethread and a "modest" chop, like only one to two inches.  That'd help reduce the length a little, get my barrel threaded to match my Tirant9, and also might look OK with a 6.5" handgaurd and the oem Sig full-length handgaurd too (with suppressor attached).  Obviously, the 6.5" handgaurd would be used for either suppressed/unsuppressed, and the full length handgaurd would be dedicated to suppressor sessions only.

Kind of a nice compromise for suppressor use, using a 6.5" Lancer CF handgaurd, and getting rid of the metric barrel threads.

One inch, from 8" to 7"...is this a good idea or just a good example of Classs3 pusification on my part? lol

View Quote


That's what I did. Went with a standard 1/2X28 threading. Much easier to work with and I kept the original handguard. End of flash hider still sticks out just a tiny bit when the can isn't on it.
Link Posted: 10/3/2016 3:03:34 PM EDT
[#35]
Here's what I came up with for when I choose to shoot non-suppressed after the 4.5" barrel chop....



A 5.5" flash hider with 1/2 x 28 threads.



With the stock length hand guard, the new FH sticks out a bit farther than the stock barrel and Sig A2 styled FH.

With my lower off being engraved, I have no range report for this config as of this writing.

Link Posted: 10/3/2016 6:07:56 PM EDT
[#36]
This has been probably covered somewhere else, but is there any difference between the 13.5" barrel and the 8"? I'' looking to cut my 13.5 pretty short and it just dawned on me that the gas system might be different.
Link Posted: 10/4/2016 9:48:13 AM EDT
[#37]
Quoted:
This has been probably covered somewhere else, but is there any difference between the 13.5" barrel and the 8"? I'' looking to cut my 13.5 pretty short and it just dawned on me that the gas system might be different.
View Quote


Well that depends on who you ask.

The sig tech guys posted somewhere in this 125+ page MPX thread on Sig Forum that cutting a carbine barrel to < 8" could give reliability issues due to diff gas port sizes.  Personally, I took that as liability management lawyer speak.   I have a 13.5 Carbine and mine was cut to 7" and runs great, without issue.  My local suppressor shop guy (Capitol Armory) said in no uncertain terms, that is BS and you can cut it as short as you want.  

Mine has been cut for a few months.   I sort of regret not going  a little shorter.

At the end of the day, the company is going to CYA and say dont go <8".   The world at large has gone shorter.   You have to make the call of what you choose to believe.    

If you cut it to 4" and it does not run, saying "Some guy on the internet said I could" is not much help.
Link Posted: 10/4/2016 3:45:41 PM EDT
[#38]
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Quoted:


Well that depends on who you ask.

The sig tech guys posted somewhere in this 125+ page MPX thread on Sig Forum that cutting a carbine barrel to < 8" could give reliability issues due to diff gas port sizes.  Personally, I took that as liability management lawyer speak.   I have a 13.5 Carbine and mine was cut to 7" and runs great, without issue.  My local suppressor shop guy (Capitol Armory) said in no uncertain terms, that is BS and you can cut it as short as you want.  

Mine has been cut for a few months.   I sort of regret not going  a little shorter.

At the end of the day, the company is going to CYA and say dont go <8".   The world at large has gone shorter.   You have to make the call of what you choose to believe.    

If you cut it to 4" and it does not run, saying "Some guy on the internet said I could" is not much help.
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This has been probably covered somewhere else, but is there any difference between the 13.5" barrel and the 8"? I'' looking to cut my 13.5 pretty short and it just dawned on me that the gas system might be different.


Well that depends on who you ask.

The sig tech guys posted somewhere in this 125+ page MPX thread on Sig Forum that cutting a carbine barrel to < 8" could give reliability issues due to diff gas port sizes.  Personally, I took that as liability management lawyer speak.   I have a 13.5 Carbine and mine was cut to 7" and runs great, without issue.  My local suppressor shop guy (Capitol Armory) said in no uncertain terms, that is BS and you can cut it as short as you want.  

Mine has been cut for a few months.   I sort of regret not going  a little shorter.

At the end of the day, the company is going to CYA and say dont go <8".   The world at large has gone shorter.   You have to make the call of what you choose to believe.    

If you cut it to 4" and it does not run, saying "Some guy on the internet said I could" is not much help.


Wow, that was a much better response than I was expecting. Ha, thanks man.

As soon as my stamp comes back in (15+ stamps and this wait hurts the most), I'll probably take the role of the sacrificial lamb and see what happens when you cut a 13.5 barrel to 4.5.
Link Posted: 10/4/2016 7:18:48 PM EDT
[#39]
Mine has been cut for about 6 months but because of the warning of reliability I only pushed it to 7" but performance has been perfect thus far!
Link Posted: 10/6/2016 6:19:38 PM EDT
[#40]
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Quoted:


TiRant 9 or .45?
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Few hundred rounds through my MPX w/AAC TiRant, zero issues with gas in the face


TiRant 9 or .45?


TiRant 45 attached via AAC's TRIAD 3-lug system.
Link Posted: 10/15/2016 9:59:03 AM EDT
[#41]
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Wow, that was a much better response than I was expecting. Ha, thanks man.

As soon as my stamp comes back in (15+ stamps and this wait hurts the most), I'll probably take the role of the sacrificial lamb and see what happens when you cut a 13.5 barrel to 4.5.
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This has been probably covered somewhere else, but is there any difference between the 13.5" barrel and the 8"? I'' looking to cut my 13.5 pretty short and it just dawned on me that the gas system might be different.


Well that depends on who you ask.

The sig tech guys posted somewhere in this 125+ page MPX thread on Sig Forum that cutting a carbine barrel to < 8" could give reliability issues due to diff gas port sizes.  Personally, I took that as liability management lawyer speak.   I have a 13.5 Carbine and mine was cut to 7" and runs great, without issue.  My local suppressor shop guy (Capitol Armory) said in no uncertain terms, that is BS and you can cut it as short as you want.  

Mine has been cut for a few months.   I sort of regret not going  a little shorter.

At the end of the day, the company is going to CYA and say dont go <8".   The world at large has gone shorter.   You have to make the call of what you choose to believe.    

If you cut it to 4" and it does not run, saying "Some guy on the internet said I could" is not much help.


Wow, that was a much better response than I was expecting. Ha, thanks man.

As soon as my stamp comes back in (15+ stamps and this wait hurts the most), I'll probably take the role of the sacrificial lamb and see what happens when you cut a 13.5 barrel to 4.5.


Apprently this guy made that test before us!

Pix thread, page=32, near bottom, user 'booj'
Carbine cut to 4.5" and some issues with hold open and gas port sizing...

Link Posted: 10/17/2016 12:26:58 AM EDT
[#42]
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Quoted:


Apprently this guy made that test before us!

Pix thread, page=32, near bottom, user 'booj'
Carbine cut to 4.5" and some issues with hold open and gas port sizing...

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Quoted:
Quoted:
This has been probably covered somewhere else, but is there any difference between the 13.5" barrel and the 8"? I'' looking to cut my 13.5 pretty short and it just dawned on me that the gas system might be different.


Well that depends on who you ask.

The sig tech guys posted somewhere in this 125+ page MPX thread on Sig Forum that cutting a carbine barrel to < 8" could give reliability issues due to diff gas port sizes.  Personally, I took that as liability management lawyer speak.   I have a 13.5 Carbine and mine was cut to 7" and runs great, without issue.  My local suppressor shop guy (Capitol Armory) said in no uncertain terms, that is BS and you can cut it as short as you want.  

Mine has been cut for a few months.   I sort of regret not going  a little shorter.

At the end of the day, the company is going to CYA and say dont go <8".   The world at large has gone shorter.   You have to make the call of what you choose to believe.    

If you cut it to 4" and it does not run, saying "Some guy on the internet said I could" is not much help.


Wow, that was a much better response than I was expecting. Ha, thanks man.

As soon as my stamp comes back in (15+ stamps and this wait hurts the most), I'll probably take the role of the sacrificial lamb and see what happens when you cut a 13.5 barrel to 4.5.


Apprently this guy made that test before us!

Pix thread, page=32, near bottom, user 'booj'
Carbine cut to 4.5" and some issues with hold open and gas port sizing...



Good find!
Link Posted: 10/19/2016 12:10:45 AM EDT
[#43]
Can confirm on the 16" carbine barrel cut down.

I cut my first MPX barrel down twice, actually.

First was from 16" to 7.25".

At 7.25" it still ran flawlessly suppressed and unsuppressed.

The second cut took it to 4.5".

Still ran flawlessly suppressed but I was only getting BHO about 25% of the time with just my Spike's Barking Spider 2 on it.

Reaming the gas port to 0.0625" fixed it.


I have a second MPX barrel now.  It's getting cut from factory 8" down to 4".  I'll report back how that goes.

But, long story short.  If you have the 16" carbine barrel, I can almost guarantee you'll be fine chopping it down to at least 7".


On a side note, I do reload and I run 147 gr Xtreme HPs at around 1000 fps, which is into +P territory or maybe still a little under depending on who you ask.

Either way, it's a full-power 9mm load.

If you're using any of those "Hush" rounds you may have more issues.
Link Posted: 10/26/2016 12:40:34 AM EDT
[#44]
I cut my barrel from 8" to 6", and I left the handguards full length. I see no reason to really shoot unsuppressed, so it works for me. In addition, I like having my support hand as far forward as possible, and with a K length can, it looks really good.

As for gas, I had some ammo that was terrible. I switched to different ammo, and it really quieted down. It is better than my standard ARs. I shoot at an outside range, so I'm well ventilated.
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