Sorry for the rant. Deleted it. I should just have ignored these idiots.  But the fix below corrected the problem and that's what's important. So try it and see if it applies. I bet you if you mpx is jamming as it is feeding this will fix it.

Ok the fix. The reason the sig mpx gen2 is not operating right if it jamming while it is feeding from mags is because it's a feeding problem, ramps are not right on the barrel. In other words your mpx jams as it's feeding a round from magazine into chamber.,

After you fire your weapon and it jams look at ejection port and round is jammed as it feeding into chamber. NOT SHORT STROKING, STOVE PIPING ECT....that's a gas problem.

It will be one or the other ramp or possible both on your barrel. You have two ramps a right and left.

Follow this procedure.

Shoot your weapon.
When it jams remove mag and look at mag and look and see which round is jamming leaving the mag. Right or left.
Repeat process to see if it is the same round that is always leaving the magazine is jamming right or left
Look in ejection port also you can verify which ramp the round is jamming on.

My case it was the left ramp it jammed on that ramp every single time. Never on the right ramp.

So I removed the barrel clamped in a vise. Slid a round on the left ramp just to see how smooth it would slide

It was catching on the left side of ramp on case lip of the 9mm round. No matter what angle I would slide it at it caught.  You could actually fell it catching and stopping the round.

When I tried it on the other ramp, the one that round was not jamming on you could actually feel the difference between the two ramps, how easily the round slid on ramp.

OK took drimel tool enlarged the LEFT ramp and worked towards the left of that ramp. Not towards the right. I also rounded the outter face around the ramp area edges smooth. No sharp edges that could catch. Smooth and round everything. My had very sharp edges

Then polished both ramps and edges smooth. Used dremil to polish with compound.

I polished ramps to a mirror finish. Just like a ramp job on a 1911.

Took a round a slid up and down on left ramp. It slid very smoothly. Did not catch on lip of brass casing where bullet is seated at any angle.

Looked at and inspected before installing. Left ramp was a bit wider dropped down even with right ramp. Look you'll see what I'm talking about. But it was very smooth with no sharp edges and 9mm round slid very smoothly as compared to before. Before I could actually stop the round against a sharp edge with the 9mm round in the ramp pushing it forward. The round was catching on the brass lip area on sharp edges as it left magazine and was pushed into the feed lip of ramp. It was catching there and jamming the gun Afterwards round caught on nothing.

Installed barrel.

Loaded the following
gen1 and gen2 mag with Winchester 124 grain fmj  
gen1 and gen2 loaded with speer 124 grain gold dot
gen1 and gen2 mag with AE 124 grain fmj

That's six magazines and 150 rounds of ammunition.

Now before I did this mod my weapon absolutely would not cycle these rds. It would jam on every other round of the winchester and speer. The AE there at the end it would shoot this ammo and jam on and off. I could not figure why this rd started to shoot a little better.

Then realized the bullet was shaped a little differently than the Winchester bullet even though both were fmj but also the brass was thicker on Winchester than brass on AE. This is how sensitive this gun was. Just the thickness of brass effected the gun.

After this modification to the feed ramp. This SIG MPX fired these rounds like a scalded dog. It shot as fast as I could pull the trigger ABSOLUTELY ZERO PROBLEM. After now being able to shoot this weapon and it work as it SHOULD I absolutely love this weapon. The look, feel, balance, handling is fantastic. This is a keeper. The gun it's self is not the problem. It's the QUALITY CONTROL AT SIG THAT'S THE PROBLEM

I can even use the gen1 mags they work flawlessly with any ammo I've used in them in this weapon and cost a LOT LESS than the gen2 mags I'm order more of the gen1 mags tonight

Now its a possibility you may need to open up and polish both ramps if they both are jamming. But mine was always jamming on the left ramp every single time.

Try what I desribed above and see if it jamming just on one feed ramp. You might be surprised.

Easy fix took fifteen minutes. Weapon runs great and shoots everything I've put throught it. If your not confident in doing something like this. Get someone that is. Like I said super easy fix took only maybe 15 minutes if that. That includes putting it back together.

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Sucks you had the frustrating problem of a high dollar fire arm not functioning properly. Gotta feel good now and while there may be some harsh feelings for Sig QC, there's gotta be some personal satisfaction for identifying and correcting the issue.

Mine has been great so far. Love this little piece.

Yeah I was pretty ticked. I knew I could fix what ever it was when ever I got the time. But it was aggravating having to do it on a gun that cost so much. Then when I did a search. I found out a LOT OF PEOPLE WERE HAVING PROBLEMS. Again too, just a very few people tried to say most all of the complaints are repeated posts done by just a few people. Then a few members bust on you for voicing your grievance. It's almost like these companies have people on gun forums defending them.

This was nothing but plain and simply poor quality control. With the mindset if we go ahead and ship them and we will fix them on a service return. I feel very strongly they shipped guns they knew did not work. Like the P320/M17 there is no way with all their testing they did not know upfront that gun had a problem when dropped.

It's impossible they didn't. They shipped them anyways. With the mindset of we will fix them later. That's wrong. What if one went off when dropped and killed someone.

I am still part owner in an accounting business with my wife. We've had this business for 35 years. If we sent in tax returns to the IRS not complete because we were to busy. Thinking the IRS will bump them later and we will fix them then. After the clients are charged interest and penalties. Guess how long we'd stay in business.

So if those that are having pretty much the same problem I described above. I bet if they go to the range and do that test above. If their weapon is jamming when feeding from the magazine. It's a easy fix. Actually if you take one that works and do just a ramp job and polish the ramps and remove rough, sharp edges. It will function even better. If your having problems with heavier bullets

If It jams like every other round, it will be one of their feed ramps is out of spec. It just needs a little widing and removing the rough sharp edges.  I discovered last night in my shooting room. I had one sharp edge I need to smooth down. I'll use a file for that. It was causing brass shavings in the upper. Especially when using a suppressor. Just one little edge easy touch up.

But yeah this weapon will eat every thing now. I ran some other ammo through last not in my GUN/WORK ROOM. Some 147, 115 grain fmj and hp everything I could find. Wolf, Tula.  Shot fantastic.

But man do they get dirty using a suppressor


When I was building my house. I wanted a GUN WORK SHOP. I live in a stilt house and down stairs I have a 12x24 concrete block room. I built my home myself so I could do anything I wanted as far a changing plans as I drove the nails.

Before the concrete was poured in my room.  I dug a hole and put a 30 gal plastic in the ground with an 2x4 in. opening in the top. Concrete was poured and in the floor is a 2x4 in opening in the concrete.

I use it to test fire my guns I work on at home.  It acts like a giant baffle so I do not bother the neighbors. Worked on my friends full autos with them there of coarse because they were the only ones allowed to possess the gun on their trust and shot full autos in there and no one heard it.

I learned early on to put a cover over it when I'm not using it. I've accidentally dropped more screws and springs and other part in that damn hole than I can count. Then lay on the floor with magnet for hours trying to grt the part out , almost like it reaches out and grabs gun parts and then laughs at you.


You know I say it's a barrel problem I really don't know. I have a IN LEAD YOU TRUST 4 inch barrel and I had to do the same exact thing to it also. To the same left ramp. So I'm up in the air over this now. Because having to do the same exact thing to two totally different barrels. Somethings not right with the recievers. But two different barrels and both had to have the left ramp widen to the left in order to function/feed.  I don't know. But as long as it works I don't care.

Glad ya found the problem and fixed it, then shared it!   You're right, these situations should not be occurring on any new firearm.  While I really like the Sig's owned, they have left me in lurch one too many times.  First time discontinuing the Sig 3000 support, then backing out on the "multi" caliber options of MPX and finally they seem to have numerous problems with their new models.

ILWT sells adjustable gas valve, and may try it.   Lots of gas and some serious ejection when running suppressed.

Yeah the adjustable gas valve is a great idea. I'm ordering one. I forgot all about those.

UPDATED

Went to range

Shot the following using both gen1 and gen2 mags both suppressed and suppressed. Suppressor used was HYBRID setup with 3 lug adaptor and 9mm end cap.

I compared the HYBRID against my GRIFFIN Resistance 9 on the MPX I actually like the HYBRID better. It's heavier but to me it sounded better and the larger size gives it more of a MP5SD look.  I used the ILWT 4.5 barrel I had to do the same ramp job as I did the factory barrel to get it to work. But I did test both and they both worked. But for this test I used the ILWT barrel. Because that's the barrel I'm using primarily.

I fired 100 rds of each of these ammo in this order.

TULA 115 grain fmj
WOLF 115 grain fmj
A.E. 124 grain fmj
Winchester NATO 124 grain fmj this is really hot ammo. Suppressed you could really tell a difference in sound.
SPEER GOLD DOT 124 grain hp

Total rounds fired 500. Did not clean or oil during shooting. Did not open the weapon. Just fired it Now before doing the ramp job there was no way this MPX would have fired and cycled any of this ammo without jamming every other round for the most part.

Results of this range visit.
The MPX shot like a scalded APE if shot everything I fed it without a single hiccup. Operated very smoothly and extremely accurate. Bolt locked back after each magazine emptied.

This is how this weapon should have shot out of the box. Simple 15 minute fix if your gun is jamming feeding from the magazine. Oh yeah it functions perfect using the gen1 mags not a single PROBLEM fed perfect.

So let's see gen2 magazines 60.00 bucks Gen1 magazines 19.00 bucks guess which ones I'm buying. 40.00 dollars for an 1/8 inch more metal on the feed lip. I don't think so.

Extremely happy with this gun now. Would trust my life with it. 500 rd test and no problems

Will be getting adjustable gas valve for it from ILWT. It's way over gassed shooting suppressed.
Also I did a few reloads so I did shoot a little more than 500 rds. Did a few mag dumps trying to get it to jam on the last two mags I reloaded. So add an additional 60 rds to total. I could not make this gun jam even though it was filthy from shooting 560 rds suppressed. I mean itsssss dirty, caked on dirty and it still shot.

The Hybird is the quietest suppressor tried on my 4.5 in ILWT barreled MPX, and the added weight helped accuracy. Due to other priorities, now use a 45 octane on it. Only problem is change in poi when shooting lighter super sonic bullet without the suppressor.  Agree a smaller port would help suppressed, and keep it cleaner.  I think he included a separate smaller  with the barrel, but will have to check.

Ordered the barrel with an increased port diam, due to reports of light cycling in Gen 2 with light bullets and fast powders.  Although now use it with hand loaded 147 grainers.  If get more money, may order the CZ open sights for it.

I have to have surgery Fri but after I get all healed up. I need to get back into reloading. I actually have a reloading/man cave building I had setup. With a recliner and 40 inch hd tv with cable.  I want to experiment with some subs for the MPX and my handguns.

I've fallen asleep a many nights during the fall and spring in there with windows open in the recliner watching tv until my wife comes looking for me around midnight

I'd love to see a close up pic of where you filed, if you can.

I'm having surgery in the morning right now. I injuried my hand. Hopefully it will be well enough later next week. I'll take it apart then. Right now I can even pick up a cup of coffee it hurts so badly.  

I did this to my gen 2 carbine. Huge improvement. Went over 300 rounds today with no issues then started to get a few ftf. Needs a little bit massaging but much happier.   200 rds of Blazer AL ran great and 175 rd off my reloads, that’s we’re i started having some ftf. My reloads were noticeably weaker and might have contributed. Happy all the aluminum ammo was 100%. In the past I couldn’t get off one mag of AL ammo with out multiple ftf.

Fantastic which ramp was giving you the problem the left one. Or did you just do a over al, ramp job.

On your ramp. With your reloads.

Remove your barrel and feel the bottom of your feed ramps. Is there Sharp squared edges on on the bottom of ramps. Clamp barrel in vise and take a reload a slide over you feed ramp as if it were being feed from magazine. You should be able to feel any areas the round is catching on.

If there is squared edge on the bottom of the feed ramp. Just smooth them. Take that edge off of them. Put a smooth roll on the edge so there's nothing squared or sharp for brass case edge to catch on

Its catching on the edge of the brass where bullet seats against the brass plus dragging across the brass. Could be something as simple as using a crimp on the case.

I'd also shoot a few hundred rounds of steel cased wolf or Tula through it. To smooth out any sharp edges. Heck maybe 500 rds of steel cased ammo.  But yeah if your getting brass shavings you've just got s sharp edge is all.
Oh one other way I find sharp edges. I take those foam ear plugs. The kind you roll up and they expand. I slide them across the ramps, they are soft enough to catch on sharp edges. You may not see.

But hey like you said at least its got brass shavings. Before it would not even shoot without jamming.

Congrats

The left feed ramp was the issue. I just was conservative with my polishing and hitting the sharp spots.  I did it a second time yesterday and it’s slick. My reloads get the Lee factory crimp.  I’m hoping going over it a second time should remedy the problems.

Edit: It was catching it on the bullet and making drag marks down the side of the brass. Im thinking I got it this time.

That is great. Im very happy that my post was able to help someone with yheir MPX. Now that its working your going to absolutely love that weapon.

Just curious did you do it to the factory barrel or was it an after market barrel. I had to do both. Which told me that it was the receiver that is out of spec. Not the barrel. I'm betting it's the same with all of these guns. So if you get a barrel, say from in lead we trust. The 4.5 in barrel. You'll more than likely have to do the same thing to it also. I did.

But this is great news. Neither of us did not have to buy the scorpion now

But I felt your pain reading your post where your mpx was jamming it seemed on every other round. After having spent that kind of money on a gun it it not work. Then a simply what 10 to 15 minute job and it's fixed.

Hey also if you don't have any. Get you some gen1 magazines after this mod your weapon WILL USE THEM with zero issuse. If you do have a little problem let know and I'll show you one last real easy mod I did to barrel it took 30 seconds. But also extend ramp a tad more to the left.

I have to keep editing my post for typing mistakes. I'm using an ipad and stylus while wearing a hand brace with a bunch of stitches in my hand on pain meds .

Good to know. Thanks for the info.

It was the factory barrel that I polished. I have one gen 2 mag and six gen 1 mags. All mags worked fine with the aluminum blazer ammo, I loaded 30 in a mag

So I loaded 7 mags of my weakest reloaded 9mm ammo (210 rounds), 4.5gr W231 115gr plated RN, and it worked problem free!   This is the first time I shot it after I polished the feedramp a 2nd time. The 1st time was a little too conservative but still cycled all 210 rounds of Blazer AL.  2nd time I polished it like I meant it especially on the left side where all my ftf were occurring.

I don’t think the gas hole has too be enlarged and I agree with firemedic that MPX ftf are probably caused by sharp edges on the feedramp. A sample of 2 so ymmv

FireMedic2000, thanks for your post and figuring this out. My MPX was jamming too but after around 300-400 rounds it smoothed out. Now at around 800 rounds all seems fine. However I just now today ran into your post and I will check my feed ramps for smoothness and possibly just polish them up some anyway.

I’m also a local Tampa guy. I usually shoot at either Gun Craft down in Ruskin because it’s a outdoor range and never really crowded or I’ll go up to Shooters World.

LOL I shoot at gun craft often. I RO there sometimes. I work on my guns there to sometimes. I very good friends with the owner and ALLIE and her husband. I've been going there for twenty years.

You've might have seen me. I drive a gray silver Hummer H3 with a Ranger licence plate. I park at the covered shed most of the time. So I can clean or work on my guns.

I just had surgery Tues so I'm out of commission for a while but we will meet. I have all kinds of suppressed guns you can shoot and I'll supply the ammo. From SCAR 17 & 16 to M40a5. I went over board and bought 9 suppressors AT ONCE

But that's a great laid back range. Just follow the rules and the members police each other. But do not screwup. Which is pretty hard to do.

Look forward to meeting you Eventually after I heal up.

Oh yeah update I'm up to 1000 rds on the MPX without cleaning it after doing the modifications to it. Zero malfunctions.

I did have one incident where the bolt did not go far enough back to cock weapon. I believe that was due to a possible weak round/charge not the weapon. That happen at around the 900 rd mark.

But I believe I'll clean it now. 1000 rds is more than enough to prove that the gun will function well enough to trust it with my life.

I usually shoot every gun I buy to 500 rds without any malfunctions before considering it trustworthy enough to use as a personal protection weapon.

But considering the problems with the GEN2 VERSION OF THE SIG MPX 1000 rds without any malfunctions was the goal.

This weapon is quickly becoming one of my favorite guns. Especially since after doing the mods it work's 1000% with GEN1 20 and 30 rd magazines. Hugh difference between 60.00 and 19.00 in cost for 30 rd magazines just for an 1/8 inch more metal on the feed lip. Oh did I mention 12.00 for the 20 rd magazines vs what 60.00 for the gen2 magazines it makes me wonder what the 1/8 of extra metal is made out of.

I'm just being a smart A I just can't figure out the logic on the magazines. If you have a GEN2 and not tried a gen1 magazine you owe it to yourself to try one and see if they work at those prices. If the the magazine doesn't do the 10 min mod above they will 100% of the time.

But if you were lucky and got a Gen2 that works flawlessly the Gen 1 magazines should work in your weapon also FLAWLESSLY

THANK YOU!!!!!

I've had this exact same issue and it's been driving me crazy. I bought these 124 grain flat tip (mostly round nose except the very tip is flat), and they wouldn't cycle through my MPX no matter what I did. But it wasn't only those, even 124 grain ball reloads had issues. I could get factory ammo to feed mostly, but I was super disappointed in how picky the gun was with ammo. I bought some 115 grain Remington, Winchester, and Remington Steel Case. They all ran without issues. I checked my ammo against the factory loads, and I couldn't find any difference in measurement. I came across this thread tonight and then tested according to what you had posted. Sure enough, I was getting failures on the left side round. I didn't waste anytime in pulling out the Dremel. It cycles so much smoother now, and I can run the rounds through the gun manually with no hiccups. I can't wait to test it at the range. I think you saved my MPX.

Just for reference, this was a 14.5" ILWT barrel, but when looking at the 8" factory pistol barrel, that looks almost the same. I will have to give it the same treatment.

Thank goodness for Firemedic and AR15.com!

Remember if you get any brass shavings you can remove the barrel and find the sharp edge you made from dremilling and missed polishing or shoot steel cased wolf or other ammo through it to smooth everything out. Which is what I did. Polish to a mirror finish.

If you need to widen the LEFT ramp. Widen to the LEFT and maybe even lower it. But just holding the barrel and with your hand. Pushing a round through the ramp/ramps you will before working on the barrel feel and see where it's catching. It will be catching though where the bullet seats. The rim of the brass.

Afterwards you can not get the round to catch at any angle you push it through. That what you want. That's how to test before firing.

Pushing a live rd by hand up the ramps and it not snagging at any angle. If it catches then you need to smooth and or remove more from ramp.

Ran 300 rounds with no issues. When I clean it I’ll see if I have brass shavings. I used to get them everywhere. Thanks again for figuring this out.

Firemedic, when you say you enlarged it to the left, what did you use to do that? Just a felt polish wheel? Or did you use a grinding stone to remove material first?

I have the same problem, left ramp wont even feed from a magazine dropping the bolt... right side is fine, feeds every time, but the left ramp wont feed anything but 115gr ball ammo.

I used elongated grinding wheel the same about the diameter as a 9mm bullet or close to it first to enlarge ramp towards left and if you look the left ramp is a little higher than right. I lowered the left lip a little also.

Use a 9mm bullet as some what of a guide as to how wide you to go. It does not take much.

Then I polished both ramps to a mirror finish. Rub your finger over the ramp area after polishing and feel for any sharp/rough areas and touch smooth them out.

Be sure to not grind and polish all of the divide between the two ramps.

When your finished take a loaded round and slide across the ramps to feel for any catching/hanging up.

Right now before you do anything the round is catching on the lip of the brass right where the bullet goes into the brass. So be sure to round off and polish the lip of the ramp good when you drop it a little. When you look at it. You'll see exactly what I'm talking about. When I say it's higher. So drop it down close to the right one in height.

Now that you've grinded and polished the feed lip ( about 15 min job) a 9mm will slide effortlessly across the feed lips at any angle and not catch, snag on the brass lip.

Before installing your barrel take a 9mm round and slide it across your ramps at different angles just to check for what I said above. If it catches polish that area some more where it's hanging up. It'll be on the lip of the ramp.

Basically everything was to sharp and catching on the brass on that left ramp, plus it was a little to narrow. Just a little. You won't screw your barrel up unless you go really crazy. It's a real easy fix

Your MPX will feed and fire any kind of 9mm round you feed it now. Out of either the gen1 or gen2 magazines.

Tell you what I'll post a pic of my feed ramps on my barrel tomorrow for you. It'll be towards the evening. But I'll take it apart and clean the barrel and post a picture.

So you can see what I did. This BARREL has had 1100 rounds fired since doing it with zero malfunctions. Before mod it malfunctioned every other round only on the  left ramp.

To be honest there's zero excuse for so many of these GEN 2 MPX leaving the plant with feeding problems. The GEN 1 is a much better weapon out the door. But with this 15 min fix it should solve any feeding problems you have.

The MPX has turned into my favor subgun I now put it right up there with the MP5SD

I just picked up a new gen 1 MPX earlier this month and haven't really put it through its paces yet, but if I encounter problems, this thread is relevant to my interests. Thank you for posting! Hitting that subscribe button.

You should not have any problems with the GEN 1 SIG MPX from everything I've read they've operated as they should without any issues.

It's the SIG GEN2 MPX that's been the problem. So I really do not think you'll have any issues at all. Everything I've read on the GEN 1 MPX has been outstanding.
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Sorry it was kinda hard getting the barrel off with my hands. I just had surgery on both. I then took 3 pictures put barrel back on and for some reason can only find one picture.
Oh well

But as your looking at picture the left ramp is to your right in the picture. It came out pretty good using phone. You can see how both ramps are even.

Left ramp was lowered and extended to to the left. You can see how I messed with the ramp divider as little as possible and beveled the edge of the ramp so there is no sharp edges.

Anyways this gives you something yo go on to compare your barrels to when looking at them. You can see a difference when you compare one that is not done to one that is done.

Oh this is a ILWT barrel. I the factory barrel is at the shop. I can't drive right now either. Which sucks.

Hope this helps some

Thanks Firemedic, I havent had a chance to do this yet, work has been jumping for the past week, but next week I will try this out and let you know.

I have a ILWT 4.5" barrel and the factory 8". The ILWT barrel is just as bad as the sig barrel. I would have thought the aftermarket would have fixed the feeding problems, but no. It is the same problem on the left side. 115 ball ammo is a 50/50 chance of feeding, but speer 124+P GDHP wont feed at all.

Funny enough, I have the MPX carbine, and that one runs just 10 times better. With 115 ball amoo its 100%, but not so reliable with any HP ammo. It still catches once in about 3 mags with the gold dots, but the pistol I cant get to run at all with speer 124 +P ammo.

If you reach out to Rob at ILWT, I know he would take care of you. That being said, I've followed Firemedics instructions and used a dremel with a sanding drum to reshape the ramp, and then polished it. Feeds EVERYTHING now.

Hey FireMedic, I just wanted to thank you again for this information. I've been able to refer a few people to this post to help them correct feeding issues as well. The MPX Owners group on Facebook thanks you too.

Your more than welcome. I'm glad it was able to help people.

It's not so much that SIG could not have fixed the problem.

It's the hassle of having to box up then go to UPS or FEDX and shipping it back.

When you can fix it yourself and for go all that shipping headache.

I really love this gun now. I used an MP5SD in the Rangers and if I had to choose between the two I think I might actually choose the MPX.

I wish they'd do the MPX in 45acp. That would be a bad azz gun right there.

Since I've fixed mine. I've not had not one single malfunction of any kind with any ammunition I've used.

MPX in 10mm for me. Now that's what I'd love. Successor to the MP5 10mm.

MPX in 10mm now your talking a very serious weapon right there. I'd buy one of those and one in 45 acp.

Alot of people just do not realize that these pistol caliber weapons are alot more effective than a 7 or 8 inch AR

A 9mm subgun using hp ammo like gold dot, hornady or federal is extremely effective. Heck even one using just 45 acp 230 grain fmj ball is very effective. That big old heavy bullet just knocks the crap out of what it hits. It's like getting hit by a MACK TRUCK.

Where as a 55 grain bullet out of a 7 or 8 inch barrel just does not have the same effect. I'm not saying you should use sub weapons for long distance shots.

But up close. With the right ammo. A 124 to 230 grain bullet will beat a 55 to 62 grain bullet out of a short barrel every time.

I'm not comparing this to 300 blk out and it's record. Totally different puppy right there. I've got one of those also and love it.

300 blk out and pistol rds are designed to work out of short barrels where as the 5.56 is not. It not the BEST choice. But if it's the ONLY choice it'll work.

Had a few jams in my Gen2 with ILWT 4.5bbl tonight. Still a new barrel but I went ahead and removed it and did a little smoothing and polishing on the feed ramps. We'll see how it goes from here on out. Thanks for the info!

Good luck make sure to give that left ramp on the barrel a little extra love.

If ILWT wants to make some cash, coming up with the conversion kits that SIG obviously won't would be tits.

Just got my Gen 2 MPX 8" SBR 2 weeks ago and was having a jam every 3 mags or so. I noticed a good bit of brass shavings inside the gun while cleaning it the first time so I decided to clean the gun really good and smooth out the feed ramps on the barrel. I have about 600 round through the gun already so I hope things will be good with this polish I did. I have some Flitz and a Dremal coming in the next few days so this is the best I could do with what I had available. I used a Scotch-Brite Heavy Duty Scour Pad to polish the feed ramps. Gonna take it out this weekend and see how she runs. If needed I will buff it up with Flitz and take a light grind to it. The way I have it now I feels a lot smoother then it did before the polishing. The AE 147Gr 9mm casing doesn't grab when you're sliding it into the barrel with your hand like it did before the polishing. If this works I might get a Gen 1 mag and see if it runs without any issues.



Pic of MPX

I wish people would stop propigating this on the internet. There is much research to the contrary that has caused departments and agencies like the FBI to switch back to the 9mm and to short barreled carbines or pdws in 556.

I have personally observed testing with gel from both subgun in length 9mms and PDW length 556.The results in hollowpoints are exactly the same in depth of penetration and expansion. However, the rifle round definitely causes more damage and a very large temporary cavity that is only effective in rounds around the 1600+ fps mark. The other difference is that the 556 does not necessarily need a hollowpoint to be effective. 62gr ball is devistating at a target at smg engagement distances where pistol rounds behave like a pistol round.

Finally, you can not compare a 45 to a mac truck. You cant compare most any small arms to a mac truck. It is simple physics if it doesnt crush you like a mac truck. If it doenst knock you over or throw you across the room when you shoot it it will not do that to your target. The same testing as the carbine we tested both 9mm and 45. Both penetrated and expanded the same. The 9mm won out because it had higher capacity, lower recoil, and better barrier performance. When compared with the original hydroshock 45 it was night in day. After observing the test I would not feel comfortable taking a hostage rescue shot with a hydroshock 45. I would rather use ball. That is a different story.

At the end of the day all small arms require shot placement.

I see you got the issue fixed and I am sorry I didnt get to read the whole thread. Did you ever send it back to Sig? What did they say?

OP....glad you got it fixed.

My neighbor has a nice Sig MPX that he let me shoot a few times.  We ran a few mags through it, and it jammed several times.  I was really amazed as how unreliable it was.  Don't know if he ever got it fixed, or even tried to fix it. For a nice weapon like that, I was shocked that it had feeding issues.

To answer your question NO I FIXED MY WEAPON MYSELF READ POST. Second do you own an mpx this is a repair post

Furthermore this post again is about a feeding problem with the MPX GEN 2 not gen 1 not a pissing match about what caliber is better.

No body gives a damn about the age old argument about which caliber is this or that. It's all personal preference.

You opened the door to caliber discussion with your lengthy post that was quoted by the gentleman a few post up.
It comes as no surprise that you object since you have a history of belligerence when someone doesn't agree with you.

This is a tech forum. Do not get this thread shut down. Save the pissing match bullshit for GD.

Thank you

No pissing match here.
Simply pointing out that caliber discussion was started by the OP himself.

Thanks guys; some great tips in here.

I'm a small FFL/SOT who's had the MPX at the top of my unicorn gun list, and about this time last year, I finally got it... well, I had it a bit before that, but the paperwork to get the damn thing converted to select fire (Sig flat out REFUSES to deal with small FFLs for LEO contracts!).

It wasn't until last week that I started having serious issues with Gen1 mags feeding it.... precisely what you've posted here - feeding issues from a Gen1 mag, into a Gen2 gun.

"Okay, fine, I'll buy a damn Gen2 mag."

That, generally, has meant better feeding, but now... now I'm wondering if the issue has been the feed ramps all along.

Time to break out the dremel!

After reading the experiences above, I do have a question. The brass shavings an indication that the ramp is too sharp, even if the system is feeding/shooting reliably?

I noticed the metal shavings whenever I shoot my Gen 2 MPXK but it's been rather reliable. I've only experienced one failure to extract and one or so failure to ejects from UMC Remington bulk ammo. This was over 680 rounds or so fired in one session.

Just shoot it and it will eventually wear to where you get less shaving. No need to touch it as long as it's feed right.

After I lightly grinded the feed ramps I had less shavings by my trigger pack (SLT-1 trigger). The brass shavings were coming from the brass casing on the ammo when I was getting jams on the feed ramps.