Finally picked up an MCX....Lower looks a bit different.

[ARCHIVED THREAD] - Finally picked up an MCX....Lower looks a bit different.

Posted: 10/9/2018 11:21:16 PM EDT

Finally found a good price on an older MCX....upon closer inspection I noticed my lower looks a bit different than those I’ve seen on other MCX’s...Seems to be a regular SIG AR15 lower with adaptor on rear instead of the more unique QD equipped lowers with a different mag release as well.

I am pretty new to these and can’t seem to find when they made this change or what the deal is.

Any info would be greatly appreciated! Assuming the MCX Geissele trigger would work with no issue?

Thanks

Posted: 10/10/2018 12:19:38 AM EDT

[#1]

It looks like a MCX hybrid, which is a M400 lower mated to a MCX upper. It’s not an old design, they came out pretty recently. Meant as a cheaper alternative to the original MCX, which was itself replaced by the Virtus.

Posted: 10/10/2018 7:43:18 AM EDT

[#2]

You got a MCX Hybrid, an AR lower on a MCX upper. Which is fine, but eventually you’ll still want to check out the MCX lower. They have a lot of nice improvements on a standard lower.

Posted: 10/10/2018 8:19:49 AM EDT

[#3]

Nice MCX Hybrid.

Posted: 10/10/2018 10:28:13 AM EDT

[#4]

Well that’s slightly disappointing....Should have looked a little closer during inspection. Picked it up so it wouldn’t be like the rest of my ARs....but I guess the bright side is it has the rear adaptor so when I decide to get a full ambi lower I can slap the adaptor on and be g2g...

Posted: 10/12/2018 9:21:39 AM EDT

[#5]

Quote History

Quoted:
Well that’s slightly disappointing....Should have looked a little closer during inspection. Picked it up so it wouldn’t be like the rest of my ARs....but I guess the bright side is it has the rear adaptor so when I decide to get a full ambi lower I can slap the adaptor on and be g2g...

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The upper is what really makes the MCX anyways. The M400 lower won't have the ambi parts, but eh, if you aren't a lefty then who cares? I have an MCX hybrid also because it was so much cheaper than the MCX. It's still a great gun. It also has the advantage of accepting all AR15 triggers, which the regular MCX lower won't. That alone is worth it.

Posted: 10/12/2018 11:26:21 AM EDT

[#6]

The lower in the pic is not an M400 lower. It looks like a standard milspec lower to me.

Posted: 10/12/2018 1:52:33 PM EDT

[#7]

Quote History

Quoted:

The upper is what really makes the MCX anyways. The M400 lower won't have the ambi parts, but eh, if you aren't a lefty then who cares? I have an MCX hybrid also because it was so much cheaper than the MCX. It's still a great gun. It also has the advantage of accepting all AR15 triggers, which the regular MCX lower won't. That alone is worth it.

View Quote

The trigger compatibility problems of the MCX are due to many hammers not tripping the firing pin safety on the bolt carrier and the increased bolt velocity breaking parts(geissele won’t warranty their normal ar15 trigger when used in an mcx) and having a normal lower does not change or lessen those problems.

Posted: 10/12/2018 3:26:32 PM EDT

[#8]

Quote History

Quoted:
The upper is what really makes the MCX anyways. The M400 lower won't have the ambi parts, but eh, if you aren't a lefty then who cares? I have an MCX hybrid also because it was so much cheaper than the MCX. It's still a great gun. It also has the advantage of accepting all AR15 triggers, which the regular MCX lower won't. That alone is worth it.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
Well that’s slightly disappointing....Should have looked a little closer during inspection. Picked it up so it wouldn’t be like the rest of my ARs....but I guess the bright side is it has the rear adaptor so when I decide to get a full ambi lower I can slap the adaptor on and be g2g...

The upper is what really makes the MCX anyways. The M400 lower won't have the ambi parts, but eh, if you aren't a lefty then who cares? I have an MCX hybrid also because it was so much cheaper than the MCX. It's still a great gun. It also has the advantage of accepting all AR15 triggers, which the regular MCX lower won't. That alone is worth it.

Posted: 10/12/2018 3:27:10 PM EDT

[#9]

Quote History

Quoted:
The trigger compatibility problems of the MCX are due to many hammers not tripping the firing pin safety on the bolt carrier and the increased bolt velocity breaking parts(geissele won’t warranty their normal ar15 trigger when used in an mcx) and having a normal lower does not change or lessen those problems.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:

The upper is what really makes the MCX anyways. The M400 lower won't have the ambi parts, but eh, if you aren't a lefty then who cares? I have an MCX hybrid also because it was so much cheaper than the MCX. It's still a great gun. It also has the advantage of accepting all AR15 triggers, which the regular MCX lower won't. That alone is worth it.

The trigger compatibility problems of the MCX are due to many hammers not tripping the firing pin safety on the bolt carrier and the increased bolt velocity breaking parts(geissele won’t warranty their normal ar15 trigger when used in an mcx) and having a normal lower does not change or lessen those problems.

I should have read further

This ^

Posted: 10/12/2018 3:27:41 PM EDT

[#10]

Quote History

Quoted:
The lower in the pic is not an M400 lower. It looks like a standard milspec lower to me.

View Quote

It's an M400 lower (unless it was changed by someone after it left SIG)

Posted: 10/12/2018 4:43:41 PM EDT

[#11]

For some reason, I thought the M400 had QD mounts.

Posted: 10/12/2018 8:56:32 PM EDT

[#12]

Quote History

Quoted:
For some reason, I thought the M400 had QD mounts.

View Quote

That's correct - some of the M400 "Elite" rifles did not have QD mounts though.

So, you're not incorrect. It's an M400 lower, though.

Posted: 10/13/2018 1:01:18 AM EDT

[#13]

Thanks for the information. Good to know.

Posted: 10/14/2018 9:22:45 PM EDT

[#14]

When I bought my MCX I considered a Hybrid due to the lower cost, but the MCX lower enhancements made it worth the extra cash.

OP, I've never seen a "true" MCX lower sold separately so you'd probably be better off selling the whole gun and buying a non-hybrid model.

Posted: 10/14/2018 9:23:22 PM EDT

[#15]

Is your gun a pistol? That barrel looks MIGHTY short!

Posted: 10/14/2018 9:25:03 PM EDT

[#16]

I see it has a brace on it .... remember if the lower started life as a rifle it will always be a rifle unless you SBR it. That could explain why it has an AR lower ... someone may of picked up a virgin lower for a pistol build.

Do they make factory MCX Hybrid pistols?

I've been out of the Sig rifle loop lately.