Update 6/25/24 to original post which is below-

After 300 rounds of the magazine locking back with rounds still in it about once every 10-15 rounds, I sent it back to the Ruger factory and they fixed it.

6/14/24- Dropped off at the gun store I purchased it.
6/24/24- Returned to gun store.  The work order states they replaced the barrel and extractor assembly, test fired with 30 rounds of American Eagle .380 ACP with no issues.

1. I fired 40 rounds of Speer Lawman FMJ with no issues, so it appears fixed.
2. The POI has changed, which is not a surprise.  Was right above the front dot at 30 feet originally, which I really liked.  Is now about 3 inches below that point at 30 feet, so basically the sight picture is to have the dot covering the target, which is ok, but not my preference.  At least it's fixed without too much hassle.


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11/1/23 Original Post

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I fired around 150 rounds out of it in three range trips.

I had this happen 5 times in the first 4 magazines in trip 1, twice in the next 3 magazines in trip 2, and now twice in 4 magazines.  So the issue does seem to be diminishing or could just be statistics.

Happens with AE 95gr FMJ and Speer Lawman 95gr TMJ.

I have been very careful to not have my thumb on the slide in a manner that would inadvertantly ride up during recoil and engage the slide stop as I thought this might be the issue at first.

I highly suspect if the way I'm holding the gun causes a more "jarring" stopping point at just the right time, the slide lock is bouncing and just barely engaging.  So while my grip may not be incorrect, a particular grip may be causing it.

I am hesitant to go through the pain of shipping it back as they will likely just swap the slide lock spring for another one with the exact same amount of strength and their employee might fire it with a grip where this doesn't happen and say it's fixed.

Just curious how many others have experienced this.

I do have more magazines on order but I doubt they would be the cause.  That's my next experiment along with different grip styles.

Have someone else shoot it.

Could be your grip. It's a tiny gun. Might be nudging the slide stop during recoil.

Thanks for both your replies.

My first thought was I was hitting the slide stop during recoil, so I deliberately changed my grip to wrap my thumb that could have been doing it under my other thumb, but it was still happening.

I will probably get a friend to try it next.

I had this issue once with a Kimber 1911. The issue was shooting heavy bullets with a wide nose, the top round in the magazine would hit the slide stop enough to lock the slide. It was an intermittent issue.  I replaced the slide stop but could have filed a little relief in the slide stop to clear the bullet nose better.

Those guns are known for taking a bit to break in, and then running anything afterwards.

The slide is stupid light, the recoil spring is very light, the mag spring is very hard for its size.  

Any imperfections, roughness etc, take a bit to smooth out, and a light slide and recoil spring won't overcome those little imperfections the way a full sized gun will. The mag spring will weaken and finally not push up hard enough to hit the slide stop.

My LCP original took 250 rounds. Had the same hiccups yours is. After that, it's been through over 2,000 rounds of everything and not a single issue. My son's LCP II just got broke in last week. It took 150 rounds. Now it eats anything. My best friend's LCP Max didn't take but 50 rounds, but he sat in front of the tv and racked the slide a few hundred times. My ex wife's took about 300, not it eats anything.

They all had little issues early. Most were failure to feed or eject, one or two every few mags. Slides locking back when the mag had rounds in it, and my son's didn't like to fully chamber a round from empty with a fully loaded mag, and would lock the slide back with rounds in it. His stopped having issues last week after the second mag he fired through it. From there he put 50rds of crappy Wolf steel through it, and 40rds of Winchester flat nose.

Thanks for all your insightful input.

Redman556- that is encouraging.  I will run a couple hundred more rounds through it before I consider returning it.

I find the size of these guns so much of a positive aspect that I really want to iron things out.

When these things occur my advice is to shoot the gun single handed, preferably with the left hand. If the problem goes away you know for sure it is your grip. We all could use more one hand/ weak hand shooting anyway

Mine went back to Ruger twice for the exact problem.  Did it with a bunch of ammo. I even recorded myself shooting and it wasn’t me.  It came back and did it a couple of times with FMJ and then worked fine.  
I am waiting on the 12 pound recoil spring from Galloway. Going to see if it helps with recoil like others say. I really like my MAX. .

Just had this issue.  It was happening on every shot sometimes.  It didn't happen with the magazine removed and is dependent on grip... sort of.  Pressure on the magazine base plate is what affects it.  I sent it to Ruger, but before I did, I'm pretty sure I diagnosed the cause.

It likely stems from the way they've designed the slide stop.  The slide stop on the LCP Max has the ejector built onto it.  The ejector protrudes forward and has a steep angle on the bottom side.  There is also a ton of slop in the way the magazine fits the magwell and a lot of front-to-rear play in the slide stop.  If I removed the slide and inserted a magazine with a round in it, then moved the slide stop up and down, there was no interference.  However, if I pushed the slide stop forward, where it would be under recoil, the ejector feature on the slide stop rides the rim on the top round in the magazine.  Moving the slide stop up and down with forward pressure rocks the magazine back and forth due to this.  I think that under recoil, the next round coming up is hitting the bottom of the ejector feature on the slide stop and activating the slide stop.  If there wasn't so much slot in the magazine fit, not so much front-to-rear play in the slide stop and/or if the ejector feature on the slide stop didn't protrude forward, it probably wouldn't be happening.

Thanks for the response and observations on the possible cause.

I haven't returned it yet as I plan on shooting it a couple more sessions, but I noticed when shooting it left handed last time that I don't have the issue, which might line up with your description.  

I will probably return it after another 200 rounds if it's still doing it.

Rarely happened when I shot it with my left hand as well.   Try doing what I described, it's an easy test.  Remove the slide, insert a magazine with one round in it.  Put forward pressure on the slide lock while moving it up and down.  See if it rides the rim on the case.  Try putting pressure on the base plate in different areas and see if any of them cause the ejector feature on the slide release to contact the rim of the cartridge when it's pushed forward.

Just picked up an LCP Max for myself, lubed before heading for the range.
First range trip was mixed; 50rds of Speer FMJ and I experienced 2 failure to feeds and 1 failure to fire.
Recoil was snappy but not uncomfortable.
Got home then kept the mag loaded overnight, manually cycled the slide 200 times and left the slide locked back overnight.

Second range trip was much better; 50rds of Blazer Brass FMJ w/o a bobble followed by 10rds of Hornady 90gr XTP, also no problems.

I'm very pleased w/the LCP Max, but dd start to experience trigger sting during the Blazer Brass testing. Any fixes for that? Thx!

Yeah, the trigger is horribly designed.  The two sharp edges at the top are what is causing the sting.  Sometimes, they will also pinch the skin on your finger and the trigger will not reset.  Filing them or changing the trigger show to an aftermarket one should fix that.

My LCR Max is on it's way back from Ruger today.  They swapped out the hammer assembly and some parts in the front according to the CS rep. I spoke with.  Will see if that fixes mine...

Edit:

Took it to the range and it functions flawlessly now!

6/25/24- Bumping up with resolution for any other Ruger LCP Max owners.

I had a similar issue when I first bought my LCP Max.
I sent it back and they fixed it with a new slide and barrel.
It still won't shoot Fiocchi FMJ, I get constant failures to feed that require a tool to get the round out.
Shoots everything else I've fed into it.

That's frustrating.   My worry was I would get it back and it would just say "Test fired and could not reproduce the problem".    I would still pursue that if I was you.  I purchased a 1000 rounds of Speer Lawman after running some AE through it first, and have test fired around 20 rounds of Hornady HP with no issues.

https://www.luckygunner.com/labs/self-defense-ammo-ballistic-tests/#380ACP

That's interesting.  I went with Hornady FTX for carry rounds.