Looking at the MPX models, would the version with the 6.5" barrel be easier to keep ammo subsonic? It has the shorter carbon fiber hand guard and does not come with the Sig brace, but i think it might be a better option when running suppressed. What say ye...?

Thanks!

There's only one model for sale right now, the 8.5" pistol.

Incorrect. Both the MPX-P-PSB (8" barrel) and the MPX-P (6.5" barrel and carbon fiber hand guards) have been released and are available.

Where have you seen the MPX P?

Here

If they are already hitting Gunbroker, dealers should be listing them shortly.

So...back to the original question - all things being equal, the 6.5" barrel should be easier to keep subsonic, correct? I know the 4.5" barrel would be ideal, but I am curious about the 6.5". Unfortunately, I am not well versed in 9mm ballistics.

And why do I keep seeing people say 8.5" barrel.  I thought it was 8".  I know that a 1/2" isn't a big deal but it's becoming confusing.

Also that picture isn't exactly trustworthy since its an old photo

Feel free to email him and ask for the specifics. It is the MPX-P.

I guess Sig does list it as an 8" barrel...my mistake.

I kind of want the brace, so I'm trying to decide if the trade-off is worth the shorter barrel since parts are not available yet.

According to LDD there are no plans for a 6.5" MPX.  

http://sigforum.com/eve/forums/a/tpc/f/320601935/m/4610068653?r=5210001873#5210001873

He has been in direct contact with SIG on this design.

The K version is the only one I have any interest in. If I was going to get an 8"+ barreled SBR it'll be 300 BLK.

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C

The answer to your question is that the 9mm round reaches it's maximal velocity somewhere around 8" and therefore shorter will be more likely to remain subsonic. The answer to your dilemma is a little more complicated. I believe both the P and PSB (brace) are the exact same gun just with and without the folding brace and mount. Though there were original plans for different sized barrels, I believe both guns are shipping with the 8" barrels. The official documentation on the Sig website confirms this, but there is a discrepancy. The diagram they have where it all blows apart to show which parts go with which guns does have the 6.5" barrel as an option and it is listed when you click the MPX-P..... and the PSB. So, yeah, that document is a little.... lacking. I can say the same for the manual as it clearly describes different sights (not dramatically different, but definitely different).
I suspect that this is a holdover from when the gun was first announced and it has gone through some changes. As of last that I saw/heard, there are 3 barrel sizes: 4.5" (K version, not released), 8" (pistol version, both released) and 16" (rifle version, not released). This was also confirmed in the TTAG review direct from a Sig rep. You will, eventually, be able to buy the barrels separately. In that case, I may buy myself a 4.5" barrel and hide it and the suppressor under the pistol length handguard for the best of both worlds.
So really, your question is whether or not you really want the folding stock and brace or not. The folder will take any AR stock once you SBR it. I have the PSB (folding stock) version and have an SBR stamp in process.
I see you're in Indiana, I'm in Cincinnati so not that physically far away and easily quickly reachable by mail. Should you decide the buy the pistol version and want the Sig Brace and folding stock, there will be a time in the near future that I don't really need it any longer and we could talk about an arrangement if you wanted....

I hate it when people talk out of their ass.

9mm MV will peak at around 16" of barrel length.

If you want to keep it subsonic, you really should stick to 147gr or heavier.  At sea level, it won't go super with any barrel length unless it's +p. Most 124gr and below will be supersonic out of anything greater than 4"

Thanks for being so friendly about it. Let me rephrase for the excessively anal out there.... 8" (really somewhere between 7-9") is going to be about the best length to maximize your velocity to length ratio. Yes, you can get another 100 fps if you DOUBLE your barrel length to 16", but that return on "investment" is so incredibly low, why even count it? No need to get an attitude about it....
http://www.ballisticsbytheinch.com/9luger.html

And I stand by the rest of my statements as well since I OWN the gun.....
Also, the MPX is surprisingly quiet even without a suppressor. I thought I noticed it the first time I took it out and my girlfriend confirmed it earlier today when she brought it up independently that she thought it was noticeably quieter than anything else at the range (a random assortment of handguns).

OK, now I am confused, the MPX-P-PSB is listed on the Sig site with both an 6.5" & 8.0" bbl.  I placed an order for one thinking it had an 6.5"bbl.  What lenght is it really????  
Is the MPX-P the same bbl length as the MPX-P-PSB???

Starting to feel like CZ.

The P and PSB that came through locally here both had 8" barrels.


Some retailers are showing the P with the 6.5" barrel because they use the stock picture from their distributor, and the distributor hasn't updated the picture to show the longer barrel even though they updated the written specs.


For instance, look at Lipsey's MPX listings:


http://www.lipseys.com/itemfinder.aspx?q=mpx


Then look at Zander's listings:


https://shop2.gzanders.com/catalogsearch/result/?q=mpx





So, retailer's using Zander's stock images will have the correct image, ones using Lipseye's will have an outdated picture (but correct specs).


Both of them show an outdated picture for the PSB, since they're showing the older brace instead of the newer SBX brace.






~eta~ That auction that "vugger" listed above was just using the stock Lipseye's image. That's a bad practice for an online seller, IMO>





 

I think there's been a lot of changes since the original announcement (hence the long wait time) and a lot of the ancillary data has been incompletely updated (even on the official website). The data sheets are correct, but there are some incorrect areas in diagrams and stuff. As far as I know, ALL the pistol models use the 8" barrel (and are currently the only things available). ALL the "K" models use the 4/4.5" barrel and there will ultimately be a 16" rifle variant. But that's it.

Which did you order? I promise though, you will love it. It shoots phenomenally well, looks sexy as hell, comes with a nice case and equipment get up (sling, brace, folding stock, etc) and is a ton of fun to just throw lead down range. I will suggest getting an open AR front sight tool. Everyone I've known has shot low out of the box (about mid front post), but my Magpul AR front sight tool didn't fit so I had to borrow someone's 2 pronged tool to get the "lollipop" view I prefer.

I called Sig yesterday to verify. The "p" version out right now has a 8" barrel.

Sig has not released the 6.5" version yet.

So its the same pistol, just doesn't have the brace.

You don't say...



Sounds like you should start trusting ARFCOM more than Gunbroker

And I'll hold out for the super-short version and add the wire stock...

Just a heads up, but it sounds like the K is a Q4 estimated release.

Well when you contact a major online vendor about which product they have in stock and that vendor (not gunbroker) tells you "I have one in my hands and it's the 6.5" barrel" you tend to believe them.

I decided to call Sig because everyone was saying it was the 8" version. So basically....never trust a reputable vendor's description of their products.

Maybe they've been confused from years of trusting their wives...

Maybe your right...

I have been looking around for awhile because I wanted the 6.5" barrel and it's marked incorrectly all over the place. I was actually getting ready to order one of them marked that way, as I was on the phone with the owner of the company verifying the 6.5" barrel. I decided to wait until I could talk to Sig directly and I am glad I did. I would have been pissed if I would have received the incorrect product.

oh well...so it goes I guess.