Jump to content
Brian Enos's Forums... Maku mozo!
MrRick

New MPX. Cycle issues

Recommended Posts

So took my brand new MPX to the range today and as I read in various places, use factory ammo before trying low PF ammo. So I started with  a 100 WWB ammo and it ran 100%. The issues started when I went to use Federal Independance ammo. First few rounds no problem then it started to short stroke. I thought maybe it was the ammo, so I used another type of ammo I had (reman) but it was worst. I lubed the rifle with the supplied Lucas oil and still same issue. So I went back to the Federal and it was pretty much a single shot rifle. Went and got some Hornady Critical Defense +P ammo and same thing so I wrapped it up from there. Rifle was cleaned and lube with CLP before going to the range. Any ideas what to looks for?

Share this post


Link to post

From what i have got from other mpx shooters on here the manufacturered 9mm is a little to long to run great in mpx.. OAL needs to be 1.12.. going to try this myself since i am having the same issues with my mpx .. have precision delta 124s coming in tomorrow.. gonna try and get some loaded and see what happens.. will post results on here

Share this post


Link to post

Update:

Took a look at it now and found the cap on the gas valve loose and easy to rotate with my thumb. Screwed it all the way in but if I'm understanding what I'm reading, there should be a roll pin holding it in place?

Share this post


Link to post

Did a bit of research and there's supposed to be a pin holding it in place. Mine is missing. So I installed a pin with the cap where it should be. Will see tomorrow how it goes. Not my actual picture but the cap I'm talking about. 

IMG_0045.JPG

Share this post


Link to post

I don't have any pin in the gas plug on either of my MPX's. Just make sure it is twisted all the way over and it should be good to go. 

Share this post


Link to post

I'm talking about the cap itself. The one with the 3 holes in front. If you remove it a rod with like 20 tiny spacer comes out. 

Share this post


Link to post

So here is the cap. This is what it looked like after the first range trip. 

IMG_2092.thumb.JPG.c9be43fbf72d216d6e59976bb6de2eff.JPG

 

Apparently there is is a pin that is supposed to hold it in place. 

 

IMG_2093.thumb.JPG.caa2625a454c5ff97edbf73ef45ac822.JPG

 

So I installed it and put a pin through it. Took to the range and still doesn't cycle. I think it even got worst. Before it would cycle enough to reset the trigger. Now it doesn't do that. 

Share this post


Link to post

So I took the pin I made out and screwed the cap all the way in.  Now I can get it to run all the ammo I put through it (didn't try my 147 ammo) and it ran fine as long as I kept the cap tight (kept coming loose). So now to figure out how to keep the cap in place. 

Share this post


Link to post

So I finally figured out the whole issue. So when my plug came out the first time, so did the spacers. I though they were just simple spacers. Found the order they are supposed to sit and this puts the cap in the right location to put the pin in the correct spot. With this done, I manage to get the gun to run pretty much anything. Was finally able to run mag after mag to the point I got tired of shooting it (about 350 rounds may be 400). Now I need a red dot since mine went out (Holosun). 

Edited by MrRick

Share this post


Link to post

Be aware,

The roll pin that holds that cap in place is "walking" out on mine, I have to press it back in every 500+ rounds or so. That cap needs to be screwed all the way for the gun to cycle properly.

 

Contacted Sig, they claim the roll pin may be damaged or worn, they are sending me a couple of new ones. I would have a couple of these pins in on hand and recommend checking this at every cleaning...

Edited by pitvpr

Share this post


Link to post

I contacted Sig, and they sent me a whole new valve. So I had a spare. 

Share this post


Link to post

My roll pin is still there - I’ve never taken it out. 

But it looks like it the cap has backed out a little bit, exposing a thread or two. Is that normal or should it be flush? 

9C21D516-6868-4FAD-9736-0520AE33CD52.jpeg

Edited by SergioSF
clarity

Share this post


Link to post

I think the cap will be able to rotate somewhat, but no more than where yours is. I think your okay as long as the pin doesn't come out and allow the plug to unscrew as much as the the picture from MrRick...

Share this post


Link to post

My MPX, after shortening the barrel to 5.125" is no longer reliably running my barely-making-powerfactor 147s, despite having the gas port opened up to .0625.

It ran it just fine before, with the full 16" barrel and .060 port. 

 

I saw MrRick's pic and thought maybe mine had the same issue. 

 

 

Share this post


Link to post
On 2/3/2017 at 9:18 PM, MrRick said:

 

IMG_0045.JPG

 

After taking another look, my cap is all the way in FLUSH, like this picture...haven't had any issues

 

Share this post


Link to post
52 minutes ago, MrRick said:

Mine looks like Sergio posted now. 

 

Yours doesn't screw all the way flush?

Share this post


Link to post
1 hour ago, SergioSF said:

 

Yours doesn't screw all the way flush?

Nope. It shoot fine though. My original valve, I screwed it all the way in and made a pin to lock it in place. Both valves work. 

Share this post


Link to post
25 minutes ago, MrRick said:

Nope. It shoot fine though. My original valve, I screwed it all the way in and made a pin to lock it in place. Both valves work. 

 

Good to hear. Thanks!

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...