LMT MARS-LS Ambi Lower Review


A while back I tried doing a google search for best AR15 lower.  There was plenty of various discussion, some people saying that any cheap lower is good enough.  Others talking about what rollmark is the coolest looking.  I saw a couple of discussions about ambidextrous lowers, various people were stating that that MARS lower was the best and had a pretty good argument for it.  That got me interested in it.

I purchased a Lewis Machine & Tool (LMT) MARS-LS lower with out furniture from Retting Inc.  I went with the the lower with out stock and grip because I have several stocks laying around and I don’t really care for the Ergo grip that comes stock on LMT lowers.  The MARS-LS came looking like this:

Just a note, the sticker on the right side had pretty gummy glue for it.  I tried a few different cleaner and finally had GooGone clean it off.  But in some of the following photos you may see some drops of water and lint from first failed attempts to clean the glue off.

What makes the MARS lower special is that it is fully ambidextrous.  It has an additional bolt catch and release on the right side.  Many ambi-lowers now have bolt releases on the right side, but this one also lets you lock the bolt to the rear.  It also has an ambi-safety, and left side mag release.  For me, the right side bolt release is a bit of a stretch to release, but not enough to be an issue.  The left side mag button isn’t as easy to use as a Norgon, but still plenty easy and fast.

The magwell is nicely flared.  When I did some rapid fire and reloading drills I felt faster.  I don’t know if I actually was, but it felt faster.
The front bottom of the receiver does seems to stick out a bit more than a normal receiver, so if you use a magwell grip you will have the flare of the magwell bite into you hand a bit.  Gives you a little more purchase if you like to hold the magwell.

LMT includes a QD socket mount in the end plate.  For those who like this feature the rifle comes with it.  If you don’t use it won’t be in your way.

The receiver extension is nicely staked, and has additional drain holes.  LMT also coats the receiver extension with a dry film lube.  When I was looking at the receiver extension, I realized it was slightly crooked, but I’ll be coming back to talk more about the receiver extension.

It appears to be a unmarked CAR buffer.

This lower comes with the LMT 2 Stage Trigger.  To me, the LMT trigger feels heavier, but crisper than some of the other 2 stage triggers I have.  I really like the trigger pull on it.  I’ll be posting up a comparison of a few different brands of 2 stage triggers later.

The white spec is lint.

The “roll marks” are nice and crisp, most likely laser cut.

Looking over the receiver, the only thing I noticed that seemed off, at first, was little burrs on the cover of the ambi-bolt catch.  I think that cover is plastic and might be pressed into place.  Running my fingernail over the burrs removed them and cleaned it right up.  A complete non-issue.

I put on an A2 pistol grip I had laying around.  Also a LMT SOPMOD stock.  Or so I thought.  Some years back I was given several stocks.  One apparently was a counterfeit LMT stock.  Didn’t know that till now.  I’ll write more about that later.  So I ended up installing a different stock.

Now I’m going to be open here.  Of the entire process of assembling an AR15 the only part that gives me an issue is lining up that damned receiver extension.  I used to use CQD sling mount that those had narrower notches for indexing on the receiver extension.  This would allow then receiver extension to rotate while I tightened the castle nut.  After all that frustration I’d gladly pay someone else to put it together straight for me.
I would not have purchased a pre-assembled lower if I had thought that this would be crooked.  I would have just purchased a stripped LMT MARS-L lower and assembled it my self.

I was curious about what would be considered acceptable in receiver extension cant.  I tried to find a specification in the TMs and FMs, but I didn’t see one.  Instructions just refer to installing the stock at the 6 o’clock position.  I reached out to a LMT rep and learned that as long as the individual parts in spec, they can’t be far enough off to cause issues.

So it seems to me that LMT is saying as long as the rifle functions, it is ok.  And this lower certainly functions fine as it is.  But at some point I will probably pull it apart and straighten out the receiver extension.

I would have done it already, but I am curious as to how many degrees it is actually off.  I’d been looking for an excuse to buy a digital protractor, so when ever that shows up you will hear more about this from me.(along with looking at some other brands and lowers)

I spent a fair bit longer here talking about the canted receiver extension then I intended too.  Outside of that I would call this lower flawless.  As for cosmetics, the forging flash was milled off and no damage or scratches out of the box.  A good trigger combined with useful ambi-controls and other nice upgrades like the well flared mag well and QD socket are very nice to have.  

For me, it is amazingly annoying that this product is so close to perfect, but someone assembled it with the receiver extension canted, and then it was inspected and pass in that condition.  Might just be all the quality assurance work that I do driving me nuts, but this has got me fixated on it.

One last note, as I posted before in the match made in hell post, this lower deviates from the standard AR15 specification.  Any improvements (or in the case of cost cutting changes by lesser companies) mean deviation from milspec.  As such, it may not work with other companies non standard parts.  So if you want to use a MARS-L lower with some after market billet or custom upper, you will want to make sure it will fit before you spend your cash on it.

All in all, I dunno if the LMT MARS is the “best” lower on the market (as I don’t own all of them for comparison).  But I think the features it has makes it hard to beat.


  1. I don’t know why I just found this article. For someone trying to find the “right” receiver for them, I thought this article was extremely helpful. I thoroughly enjoyed seeing the close-up images along with an explanation to what what pictures (the crooked receiver extension, burrs in the material etc).

    Please tell me Mr. Howard does more reviews (Ambi LWRC lower?).

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