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MPX tips and tricks?


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Last season, I ran a QC10 Colt pattern build (QC10 upper/lower, KVP barrel/bolt) and after switching from Hiperfire to a Timney drop in, it became boringly reliable.  I'd clean it, run a practice session (~200 rounds), then a match (~250 rounds), then repeat.  Over the entire season, I never had a failure that wasn't related to the Hiperfire.  As much as I loved it, I wanted something a little softer shooting and didn't want to fight with tuning which always seems to introduce function issues.

 

For some reason, the new MPX PCC has really grabbed my attention.  With matches starting in about a month, I decided to go ahead and grab one so I could get some range time with it.  From you guys who have run the MPX platform in matches, is there anything I should know or look out for?

 

I've got the MPX and 4 extra mags coming.  It will wear either a click switch C-more (currently on the QC10) or an RTS2 (spare).  Any other gadgets/gizmos I should grab?

 

Thanks!

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You will need to clean more often. Clean the gas plug regularly along with the bolt and carrier and also the chamber locking lugs.

An AR-10 chamber brush works pretty well for the chamber and locking lugs.

From my experience you will want some spare firing pin springs.

The extra cleaning is worth it to me over the AR9 for the way it shoots.

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The TF magwell is nice (inexpensive & attractive.)  Practice reloads a lot... that curved mag will give you endless seating fumbles if you're used to the straight colt mags.  Coming from a colt pattern Tavor to the MPX this was a big issue.  The TF mag extensions are great, though there's lots of options there and I haven't heard anything bad about any of them really.  You'll need a couple unless you're just shooting PCC in IDPA. 

 

I'm a lefty so I grabbed the wider bladed Raptor charging handle, plus the elevated rear piece solved the issue of the handle rubbing the receiver.  Not sure if that's an issue with the new Gen 3.

 

Hiperfire ECL has been perfectly reliable (knock on wood), but not an issue with the new one given the built-in Timney.

 

Don't try and tune the ammo.  Buy (or load) the hottest, cheapest factory stuff you can get, then marvel at how it's so much softer than the best tuned blowback with tricky -P loads with perfect reliability.  

 

Edit:  as Gregg said, don't forget to clean regularly.  For a piston gun it gets pretty dirty.  Fortunately it's a snap to totally disassemble, especially the great barrel arrangement with 2 bolts to pull.  Haven't broken a pin or pin spring in nearly 10K rounds, but the extractor spring should be replaced at 5K rounds, and they're serious about that.  Fortunately a dozen of them are like $10.  Several places make full parts kits that have all this stuff and more.

Edited by NervousEnergy
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I really like the Odin Works extended mag releases. I installed only the right hand side and gave the other side to a lefty shooter.

I have the Timney 683 trigger in my gun now and like it. That is the stock trigger in your gun now.

I haven't looked at the stock of the new pcc version of the mpx but switching out from the folder I had to a more traditional AR tube and stock through the help of the Thordsen adaptor was nice.

Again, I haven't felt the hand guard of the latest version but I feel the carbon fiber Isler Customs one is worth every penny/dollar.

Extra gas plug and tappet.

Couple of +10 mag extensions for a few mags.

 

And as I learned, do not chase the lightest load possible. You will only frustrate yourself. Instead chase the more reliable load.

Edited by rowdyb
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The new MPX PCC has an improved charging handle. It’s designed like an NLA/Raptor to protect the receiver. A friend just picked up one last week and it’s fun too shoot. The slimmed down mlok handguard feels great too compared to the old ones.

 

I mounted a crimson Trace green laser on mine in addition to a 6 MOA slide ride and a red dot mounted on a 45* warne mount. Also bought some spare parts from ILWT such as firing pin and springs, gas rings etc.

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3 hours ago, rowdyb said:

I really like the Odin Works extended mag releases. I installed only the right hand side and gave the other side to a lefty shooter.

I have the Timney 683 trigger in my gun now and like it. That is the stock trigger in your gun now.

I haven't looked at the stock of the new pcc version of the mpx but switching out from the folder I had to a more traditional AR tube and stock through the help of the Thordsen adaptor was nice.

Again, I haven't felt the hand guard of the latest version but I feel the carbon fiber Isler Customs one is worth every penny/dollar.

Extra gas plug and tappet.

Couple of +10 mag extensions for a few mags.

 

And as I learned, do not chase the lightest load possible. You will only frustrate yourself. Instead chase the more reliable load.

The stock 16" sig hand guard is 11.2oz

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I would agree with the addition of a mag well funnel.  Reloads take a little practice.  I went with the Taran Tatical. Great quality as one would expect.  Haven’t seen one of the new ones yet but looks like they fixed most if the stuff you had to upgrade on the Gen 1 and 2’s.  I also run one of the TF +20 base pads , haven’t got much time on it but so far working fine. 

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Gen 2/PCC's will have a smaller gas port and they like a slower burn rate/hotter ammo.

 

Not that it's a BAD thing, but I run Gen 1's and with the larger gas port, I can run my production ammo (3.3TG under a 135 blue or a 3.5 Clays under a 124 JHP) and the impulse is ridiculously short/soft. Factory 115's still aren't bad, but it's worth the $60 IMO to have the port opened up. Also watch out for the feed ramp on the LH side. They may have fixed this in the PCC model, but it's notorious for causing issues on the Gen 2's. 

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In Lead We Trust - Robert Otte.

 

I would recommend joining the MPX Owners FB group if you use that platform. I would send an e-mail to Robert and tell him what you're thinking about running. I believe he has the service listed on his site. 

 

He can also polish/shape that LH feedramp while it's there I believe. 

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2 hours ago, Acer2428 said:

In Lead We Trust - Robert Otte.

 

I would recommend joining the MPX Owners FB group if you use that platform. I would send an e-mail to Robert and tell him what you're thinking about running. I believe he has the service listed on his site. 

 

He can also polish/shape that LH feedramp while it's there I believe. 

Thanks, not in possession of any PCC, just considering getting into it and am looking at options. 

Mark

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Thanks for all of the information!  Got my hands on the MPX last night and it's pretty darn nice out of the box. 

 

Hitting the range this weekend, but here's my observations/opinions so far:

 

 - Feels a little front heavy compared to my AR9, but I expected as much as that's a 5.25 lb build with a ~19 oz barrel.

 - Trigger is exactly 4.5 lbs over a 10 pull average and no creep

 - Stock is surprisingly comfortable but I'll withhold judgment until I've put a few hundred rounds through it

 - RTS2 was to low, C-More on AD-QD mount was to high, and C-More on the factory base is perfect

 - Love the ease of disassembly

 

Ordered an Odin mag release and some TTI +11s.  A magwell is on the list, but I want to practice reloads for a bit to figure out if the Springer will work or if I have to go with a full sized.

 

On a side note, Sig must have run out of oil the day they built mine, it was pretty much bone dry.  A good cleaning and lube and she's ready to go!   

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12 hours ago, gunner01 said:

I just replaced my hand guard with the Isler carbon fiber and am kicking myself that I didn't do it 6 months ago.  The size, shape, and weight are so much better.  You won't see as much of an improvement over the new hand guard on the PCC model.

The new handguard on the MPX 16" barrel is 11.2 0z

My Isler handguard is 5.50z

Edited by Rolex
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15 minutes ago, Rolex said:

The new handguard on the MPOX 16" barrel is 11.2 0z

My Isler handguard is 5.50z

So your CF handguard is 1/2 the weight of the new models and people are still changing out the trigger...what was it we were getting out of the new model? I remember now, a longer heavier barrel that we can change the comp on that may or may not have any real effect. 😶

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Agree with lots of the things here. 

 

The thing shoots factory 115 ammo with perfection. Makes it hard to want to reload for this gun. It does like it HOT! 

 

Coming from a Glock lower, 100% agree on the magwell with the curved mags. Practice. Practice. Practice. 

 

And yeah.. It gets crazy dirty. I try to clean at 1000rd intervals at max. 

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9 hours ago, gunner01 said:

I just replaced my hand guard with the Isler carbon fiber and am kicking myself that I didn't do it 6 months ago.  The size, shape, and weight are so much better.  You won't see as much of an improvement over the new hand guard on the PCC model.

 

When I say you won't see as much improvement with the new hand guard I am referring to the fact that the new PCC hand guard is already smaller in diameter and feels better, so it is not as dramatic an improvement.  Still a great improvement to go to the round Isler, and still a great weight improvement.

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52 minutes ago, Gregg K said:

So your CF handguard is 1/2 the weight of the new models and people are still changing out the trigger...what was it we were getting out of the new model? I remember now, a longer heavier barrel that we can change the comp on that may or may not have any real effect. 😶

 

Quite a bit, actually.  For ~$1,600 street price, you get a 4.5 lb Timney trigger with no creep, a handguard that weighs 11 oz and is comfortable, and a useful stock.  It's something you can buy, clean, throw a red dot on, and go shoot a full season of matches with. 

 

Or, you can buy a gen 2 for ~$1,400 street price, get a trigger that most feel has to be replaced, a handguard that isn't exactly suited for competition, and a stock that definitely isn't built for comfort.  Most definitely not something you will want to throw a red dot on and shoot a full season of matches with.

 

On the barrel thing: If you want to play with brakes/suppressor mounts, it's fantastic and that wasn't something you could do with the pinned/welded barrel.  If you absolutely HATE the extra length, you can select the exact brake you want and have the barrel cut and the brake pinned/welded.

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4 hours ago, Gregg K said:

So your CF handguard is 1/2 the weight of the new models and people are still changing out the trigger...what was it we were getting out of the new model? I remember now, a longer heavier barrel that we can change the comp on that may or may not have any real effect. 😶

YOU R exactly correct- Have changed the Timney- stock handguard- and the stock- 16" barrel extremely accurate- BUT- TO LONG_

so now looking for a 8" 😂

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Made it to the range on Saturday afternoon and ran 250 rounds though the MPX and I'm pretty well thrilled with the way it handles.  Double taps were unfairly easy, and a 30 round mag dump as fast as I could pull the trigger resulted in a ~2 inch hole in the target at 20 yards.  Of the 250 rounds, 200 were S&B 115 grain stuff and the rest were Magtech 124.  In my AR9, the 115 grain stuff caused significantly more dot bounce, but with the MPX even when I mixed them up randomly in the mag, I couldn't tell a difference.

 

Next stop is ILWT to pick up some spare parts.  Is there any reason not to go with their spare parts kit vs. buying individual bits? 

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Other than you might get some stuff you may not need, no.  The ILWT kit is excellent.  I went with individual parts from ILWT (in addition to dropping quite a bit on two of his barrels) as I already had extra gas assemblies/tappets.  Having an extra tappet is nice but not necessary... they're very unlikely to break, and the extra is mainly just to make cleaning easier (you can drop it in an ultrasonic cleaner overnight.)  You really need extractor springs - those should be changed at 5K rounds lest you risk totally ruining a stage.  Having a spare firing pin/spring is nice.

 

I'm approaching 10K rounds, and will likely replace the main springs, firing pin & spring, and extractor spring before March.  Purely defensive - the gun runs fine right now, but I prefer not to be surprised at match time.

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