Ok I think I'm done until my GEN2 K handguard shows up. It's ordered along with the grip.

Can I ask where you purchased the CF pieces for the rails?

There centurion arms cmr rail covers. I got mine at operational parts. I think they were the last set. Comes with 3 panels. I used the screws that came with my sig rails. Cut one rail down to fit behind the hand stop.

quote:

Originally posted by scubacuba:

VERY INTERESTING! Cutting the barrel on the 8" model to 4.5" and configuring it as you've described above (with a somewhat covered suppressor) is something I had not considered. I have a Ti-Rant I'd love to put on it and I think it would look very nice like that!

That's what I have planned for mine as well. I have an omega 9k in jail - once it's approved (or simply getting close to approved) I'll be shipping the gun off to get that barrel chopped down and threaded. Can't wait!

MPX Gen 1 4.5" barrel cut and 8" rail
3 lug under the rail to Tirant 45S
Not greatest photos will post more later
[IMG:left] [/IMG]

[IMG:left] [/IMG]

quote:

Originally posted by ivy6t5:
Here is a 39-cent solution to the cold/hard cheek weld on the KM stock. I purchased a 1-foot length of 3/8" I.D. x 1/2" O.D. Clear Tubing from the plumbing department at Home Depot for 39 cents. I cut off a 5-1/2" length and slit it on one side down the length of the tube and placed it on the top rail of the KM stock. Much better feel - softer and warmer!

Great idea. No doubt SIG will make a version of this and market it for $39, SIG Logo and all. And many would probably buy it too! ;-)

quote:

Originally posted by tbuck:
Ok I think I'm done until my GEN2 K handguard shows up. It's ordered along with the grip.



SNIP!

That weapon looks fantastic! With the KM stock and 4.5 " barrel w/ flash hider, what's your total length? Just curious what you ended up with for your SBR paperwork which I'll be doing shortly here myself...

Thanks!

My factory Gen 1 K SBR came in last week. The form4 will be filed this week.

Here are a couple videos of me and a buddy shooting two different MPXs last weekend. One was a cut down full-auto K, the other was semi-auto 8". Both are suppressed. I was AMAZED at how controllable this gun is. Gotta get me a Keymod K now.

https://youtu.be/S09snpHOIf4

https://youtu.be/3a_ALlA6uhU

Ok, I want to cut down my barrel to the right length so that it's flush with the 4.5" K hand guard, not including a flash hider. I'll generally have a thread protector on the barrel, and pull it off and install my suppressor when shooting.

SO what length do I have to have my barrel cut down too in order to have it be approximately flush with the end of the K hand guard?

From the pictures I've seen, it appears a 4.5 barrel is in fact inside the hand guard, and it extends out only because of the flash hider.

So do I need to go 4.75", 5" or?

Thanks!

quote:

Originally posted by AggiePhil:
Here are a couple videos of me and a buddy shooting two different MPXs last weekend. One was a cut down full-auto K, the other was semi-auto 8". Both are suppressed. I was AMAZED at how controllable this gun is. Gotta get me a Keymod K now.

https://youtu.be/S09snpHOIf4

https://youtu.be/3a_ALlA6uhU

Cool stuff, thanks for sharing!

Received the keymod MPX foregrip/hand stop today, ordered at the end of January. Seems very nice, now to wait for the 4.5" hand guard!

quote:

Originally posted by SuperPollito:

quote:

Originally posted by dwd1985:

quote:

Originally posted by SuperPollito:
FYI (and this may depend on examiner) but my Form 1 was rejected because I listed the item as Sig MPX-P rather than Sig MPX.

Yup, I had the same thing happen. Re-submit with just "MPX", then call your examiner with your old and new case numbers. They will expedite the
process, and it should only take an extra 4 or 5 days.

That's what I ended up doing as well. Only took 3 hours or so but we got it worked out. After redoing the paperwork, I believe the MPX-P was an option in their dropdown menu, i.e., not something I personally put in. But at any rate, all is well and my lovely telescoping stock can now be mounted.

I put MPX-PSB and I received my stamp on Thursday with no issues....guess I got a lenient examiner!

Help me choose a RDS mount.

Based on some luck, I am getting an Aimpoint T2 at an incredible discount. What I need to do now is decide how to mount that on my soon-to-be-ordered MPX.

What mount should I use if I think this sight will stay on the MPX making QR helpful but not necessary?

I "think" I would like to pull off absolute co-witness with the stock MPX sights, if possible. But I am willing to be dissuaded if the height requirements for absolute co-witness leads to cheekweld/head position sighting challenges.

I have not decided on a stock once the SBR stamp is available. Leaning more toward telescoping/collapsing rather than swinging (KM).

I can get the Aimpoint LRP at the same discount as the sight.

I REALLY like the look for forward cant of the Fortis mount that Steve has used.

I have looked at the Scalarworks LDM as well.

And then there are the Larue options, but those are all QR, but come in a variety of heights.

Or I can go cheap with the RDSM-4H (ACW) to start.

Any advice appreciated.

ETA: Does anyone have a current ETA for the MPX-K local shops?

quote:

Originally posted by ctsheepdog:
I "think" I would like to pull off absolute co-witness with the stock MPX sights, if possible. But I am willing to be dissuaded if the height requirements for absolute co-witness leads to cheekweld/head position sighting challenges.

The factory sights on the MPX are shorter than standard same-plane AR-15-height sights. A sight base that is normally "Absolute" may actually result in a "lower 1/3" when used with the factory MPX sights.

Thanks guys.

dwd, are you talking about this mount or just the spacer (adapter) shown above the micro mount?

https://danieldefense.com/moun...lute-co-witness.html

quote:

Originally posted by dwd1985:

Just the spacer itself. I ordered the lower 1/3rd mount, which is an absolute mount with a spacer you can add on to raise it to lower 1/3rd. I used the absolute mount on one H1, and then used the spacer with a factory mount on the H1 I mounted on the MPX.

So Aimpoint factory mount AND the DD spacer on the MPX? And you got absolute with both combinations?

For a reformed engineer, I can be a dump sh1t at times.

Thanks.

Anyone else with thoughts on T2 mounts in MPX?

quote:

Originally posted by ctsheepdog:
For a reformed engineer, I can be a dump sh1t at times.

Thanks.

Anyone else with thoughts on T2 mounts in MPX?

I would recommend the Trijicon MRO. I have them on all my SBR's and AK-74. It's the best RDS I've ever had and I like better then the Aimpoint. Whichever one you get I would also recommend a QD mount. I use the American Defense.

Hey all, I just wanted to introduce myself and thank you guys for the info in this thread. It's has been a great resource in figuring out what to buy and how to do my build. I ordered a MPX-P that should arrive at my FFL today. My plans are to SBR it with the telescoping stock (though I wish Sig hadn't switched to the shorter rails, I'll take what I can get.) I've got a Rugged Suppressors Octane 45 that's on it's way to the retailer and I chose that can based on what I read in this thread. I plan to e-file the forms under my trust so that, hopefully, everything will be granted, or at least submitted, prior to 41p going into effect.

The optic will be a Vortex SPR-1301 Spitfire 1x Prism scope. As much as I'd like to have an AimPoint RD sight, red dots and holographic sights don't play nicely with my astigmatism.

In any case, I very much appreciate all the knowledge here and am happy to no longer be a lurker!