There are a couple of issues that I'd like to see addressed in the 2nd Gen guns. The charging handle slap marring the receiver is one. Another is the barrel retention screws. The Military Arms Channel mentioned that his barrel started to come loose at about 1K rounds due to these screws walking out. That would not happen if they used something like the SCAR's ratchet screws.

This message has been edited. Last edited by: Sensei,

^^^ Yep, that sums it up nicely for me as well. Mostly being able to Form 1 it now. Though, I'm just planning on having my barrel cut down.

quote:

Originally posted by argolfer:
I'm going to have my barrel cut down to 4.5" and put a 3-lug adapter on it. Does it matter if I go with the 1/2x28 or the 13.5x1? I will match the thread to the one I order of course, just didn't know if it mattered.

Like everything there are pros & cons either way.

Availability: Win for 1/2x28 since there are multiple sources for 3 lug adapters from TrosUSA himself, Brownell’s carries them (limited stock though), HK Parts, TheSilencerStore and more just do a Google search. When I bought mine from Tros I got them within a week since he had them ready to go. However when I bought my MPX TrosUSA was the only place to get a M13.5x1 and it took almost 3 months due to various issues even though I was told 2-3 weeks, he did eventually deliver and it was at the quality I expected. Now HK parts started carrying them and are likely made by Tros but they at least carry inventory and won’t be a special order. As far as I know, those are you only two choices.

Compactness: Win to 1/2x28. The metric is larger in diameter and therefore the 3 lug portion doesn’t start until after the barrel threads end. The 1/2x28 can fit inside the 3 lug therefore there is no unnecessary addition to length other than what is required for the 3 lug portion. I discussed this and attached photos in one of my previous post.

Accuracy: Win to M13.5x1 (Probably). Not tested but reasonable theory. According to the CEO of MasterPiece Arms he claims there can some accuracy lost when using 1/2x28 threads due to the smaller amount of metal remaining at the end of the barrel and for pure accuracy once recommended to me a non-threaded barrel or thicker thread diameter on a custom barrel. Therefore on that same assumption, it would reason to say the M13.5 would be a safer bet since more metal is left between the barrel groves and deepest part of the thread. Just like you could thread a .300 BLK in 1/2x28 but why would you when you could use 5/8x24 and leave more barrel at the muzzle). There may be no real gain but something to consider.

Reliability: Win to M13.5x1 (Probably). One of the advantages of a reverse thread is it generally acts against the rotation of the barrel causing the mount/can to become tighter as it’s fired. This was something I’ve heard touted as an advantage of the MPX on several occasions. I do know my 1/2x28 pistol cans need to be re-tightened about every 5-10 shots and it’s very annoying! I used red Loctite on my mount anyways so probably not going anywhere either way, but you can’t tighten the mounts down as hard as a normal rifle QD mount since there are not flats on them in which to use a wrench. So the reverse thread helps reduce the chance of it loosing and causing a baffle strike. To me is a pretty cool aspect of the metric thread. With that said I still use 1/2x28 Tros mounts on other carbines.

In the end it probably doesn’t really matter either way but there are slight differences.

Found another option that is new on the market, Griffin now makes/sells them too. Little more expensive at $70 each but they look like they're high quality from the pictures.

http://www.griffinarmament.com...g-Adapters-p/93l.htm

I really wish Sig would release the sliding stocks. Just got the email my form 1 is approved. Ordered my stock at the same time so the ATF is now more organized than Sig in my opinion!

quote:

Originally posted by Dano36:
I really wish Sig would release the sliding stocks. Just got the email my form 1 is approved. Ordered my stock at the same time so the ATF is now more organized than Sig in my opinion!

Sig is doing this sign, hope, pray and wait as a business decision. They know the public will buy the pistol and hope that the stocks will be available soon. They are filling up law enforcement orders first and then will release the stocks at a later date. Once supply matches demand. People will wait. They will lose some orders but most will wait.

That not a good reputation to be building. "Slower than the ATF".

I don't see a lot of LE agencies going for the MPX right now. Can't imagine why they won't service the civilian market since it so much larger. Very H&K'ish of them.

quote:

Originally posted by Dano36:
I really wish Sig would release the sliding stocks. Just got the email my form 1 is approved. Ordered my stock at the same time so the ATF is now more organized than Sig in my opinion!

Never owned or applied for SbR before, could an MPX with sig brace be form 1'd and used until the sliding stock is available?

Scott Springer at Springer Precision has come up with a plus 10 magazine extension for the MPX. They are being anodized on Monday and should be up at his website soon at http://shop.springerprecision.com/main.sc

Me Want

quote:

Originally posted by Hebrew Hammer:

quote:

Originally posted by Dano36:
I really wish Sig would release the sliding stocks. Just got the email my form 1 is approved. Ordered my stock at the same time so the ATF is now more organized than Sig in my opinion!

Sig is doing this sign, hope, pray and wait as a business decision. They know the public will buy the pistol and hope that the stocks will be available soon. They are filling up law enforcement orders first and then will release the stocks at a later date. Once supply matches demand. People will wait. They will lose some orders but most will wait.

Concur with above comments. What I want is a multi-caliber MPX SBR Suppressed and many factors are affecting that desire. For example, there are "time" factors other than waiting for SIG to finish up filling LE orders for stocks and suppressors before opening to civilian market:
1. ATF 41P review is now Dec 2015; who knows what will happen with regard to Form 1s and 4s for SBR and Suppressors?
2. The ATP 41P fear factor will have folks rushing to get Form 1s under a trust and bogging down ATF's bureaucracy even more?
3. When will SIG release to the public telescoping, folding stocks and the MPX suppressors?
4. After market MPX items are already showing up and will these items work with Gen 2 MPX?
5. I know all the above factors have workarounds and different purchase options, but increased hassle to the customer will drive away customers.

However, I going to stay optimistic and plan a purchase after the Gen 2 MPX, stock options and suppressors arrive; and assume the ATF 41P will be trashed.

Picked up the MPX with the Sig brace yesterday. Will be calling Sig tomorrow about the three mags. I'm going to hold off on doing the SBR for now. Want to make sure a can get more mags first, and would rather wait for the shorter hand guards to show up so I can run a shorter barrel. I test fired it today with different types of ammo, and had no issues. I will be getting a three lug adapter from Griffin or Tros for the suppressor hopefully before winter.

Is every MPX upper the almost plum color like the above picture? If so, why? The rail and lower look flat black.

quote:

Originally posted by Elec540:
Picked up the MPX with the Sig brace yesterday. Will be calling Sig tomorrow about the three mags. I'm going to hold off on doing the SBR for now. Want to make sure a can get more mags first, and would rather wait for the shorter hand guards to show up so I can run a shorter barrel. I test fired it today with different types of ammo, and had no issues. I will be getting a three lug adapter from Griffin or Tros for the suppressor hopefully before winter.

What is your reason for running the shorter hand guards if you have a shorter barrel?

The end of muzzle would be in the hand guard. Want the option to run it with or without the suppressor.

You still can do that. It will just stick inside the rail a little (or a lot). A 9mm can is not going to get hot enough to worry about like you would have to a centerfire can. My barrel is being cut down to 4.5" now and I'll keep the hand guard 8".

I don't have it done yet, but it would look similar to my AR9:

Would like to be able to use it with and without the suppressor. I did the suppressor under the hand guard with my 9mm AR, but building a second upper was easy and not a lot of money. Right now I hoping to get some mags for the Sig.

Anyone running any foregrip on their MPX? Wondering what options are out there. There's an aluminum one I've seen online, but not many other options.

Ahhhhh. Just sold my 9mm AR and can't decide if I want one now or wait until a gen 2 or carbine come out.

I purchased a MPX PSB few weeks ago. Had a Colt 9mm and an HK UMP/USC Close. No comparison IMO. Compares well with a SP89, but costs a whole lot less and I don't mind it getting dinged up like I did with the 89.

Colt and UMP were fine, but too large. Blowback and dirty as hell. Limited in use for what they are made for compared to the MPX.

The MPX has one issue for those that like to "keep it pretty" the charging handle droop. Easily fixed by a small piece of velcro or ignored by locking the bolt back before loading.

Is it an oversight by Sig? yes. Will the Gen 2 fix it? Don't know.
That is my only issue so far, and I've soon forgot about it being a problem. Took a chance knowing all this before I got it and guess what, I like it a lot anyway.

Good to go though a couple of hundred rounds.