I picked up my first Glock this week, a G42.  I picked up 2 boxes of 90gr fmj PMC and a box of Hornady critical defense 90gr FTX. It was all I could find local. Good size, weight and soft shooting. I had knee surgery Wednesday, so I've only put about 50 rounds through it. It shoots a nice group at 10 yards, plenty enough for SD. After my knee feels better, I will shoot a couple more hundred rounds through it before I make any negative judgements. As I said, I really like the size, feel and soft shooting of the G42. I am hoping the minor issues aren't chronic. I doubt they are.

There are two issues I am slightly concerned about. The first two mags of PMC wouldn't eject the case and load the next. This failure eventually stopped and worked fine through the remaining mags. I chalked it up to break in. The second minor issue is more me than the gun. I think my thumb is riding the slide stop, preventing lock back on empty.

Am I correct to assume the first issue was break in and does anyone else have a lock back on empty issue?

Edi: i am not in any way trying to give a negative review. I haven't shot it enough for that. The issue only happened a few times. The 42 is a well designed gun that shoots very accurately, soft shooting and easy to carry.

I would say probably on both counts. I have 2 ( 1 is the wifes ) and both had a few hiccups the first few mags, but have ran fine since. Neither one has had lock back problems.

You have to use a low thumb grip with the 42. anything that slows down the slide, like your thumbs touching it, will induce stoppages. Mine had a chamber flaw that needed to be removed before it would function. others function great from day one.

There have been all sorts of issues reported with G42 pistols..however many new owners(me included) report no issues at all. Some pistols seem to stumble a few times at first and come-up running fine too..

On another Glock forum there was a pic of a new G42 pistol with a horribly mis-machined barrel crown!  Like other gun-makers..Glock is turning out a turd here and there, this for sure.

I would try some different ammunition before getting too excited. Not locking open and sometimes not ejecting or loading sounds like weak ammo(or limp-wristing)..gun may have a really stiff recoil spring assembly too. I've read of other owners saying their G42 required hotter ammo for reliable function.

Ammunition I've fired through my new G42 includes Federal 95gr TMJ RTP(range/target/plinking)...Federal AE 95gr FMJ...old old Federal 95gr FMJ(like from the early 1990's)...and the Hornady 'Critical Defense' 90gr ammo...no jams or failures of any sort with my pistol and those loads.

I will say that I shot a couple hundred rounds of the Federal RTP ball ammo from my new G42 before I bought and tried the Hornady ammo. Most new pistols I buy get a  full metal jacket break-in and clean/lube after every shoot until I feel it's good to go.

Seriously the only thing my G42 needed was the rear sight 'budged over' to the right a bit to sight it in.

In all fairness, I could have been limp wristing. Even though I shoot a lot, I was trying to feel the trigger and such. I could have been loosening my grip a bit. The chamber looks fine. The feed ramp has two little chamfers at the top of the ramp. I have never had a glock. Since the two chamfers are polished, I assume it is normal.

Otherwise, I am fine with it so far. Many guns I've had needed break in.

My chamber/feedramp is the same as you describe...couple polished chamfers on either side with some polishing between them.

Just picked up my brand new 42 Friday and shot it today.  Perfect reliability with cci blazer Remington and Winchester hollow points. I was a little worried about the Winchester as the cavity is huge. Tiny little close in rapid fire groups. Slowing it down 15 yard group ran roughly 2 inches and went right to point of aim.
I like the size weight reliability and accuracy. As a long time revolver guy this may actually replace my 30 year relationship with my j frame.

Getting mine to run reliably has been a challenge.

Out of the box I got all sorts of issues, mostly, failure to feed, then failures to lock back.  This was with Federal white box, and PMC.

I then got some RWS Geco ammo as it has a reputation of being above average power.  I never had so many problems with ammo before.  The same failures to feed, no more failures to lock back but now lots of stove pipes and light primer strikes, about 10 per box of 50.  Some ammo will go after a second strike but some wont.

I then started looking at the failures individually.  The failures to feed - I rounded the lower inside corner of the extractor and saw some improvement.  A friend noticed there were some molding deformities inside my mags, right below the feed lips.  Look like some molding flash.  I suspected this was slowing the rounds down so I dremeled those areas smooth.  Also polished the chamber and feed ramps and filed the edge of the ejector, closest to the rounds in magazine.

I have less FTfeed, but still get the light strikes and occasional stovepipe with the RWS Geco ammo.   I shot an entire box of Fed white box with no failures, I am now loading the gun to 6+1 for all testing.  A box of S&B also ran without issue.

I got some Winchester Train and Defend ammo from Cabella's last week and have ran through 200rnds of the training ammo and 20rnds of the defend ammo.  Just one stovepipe with the training ammo.  

My friend gave me 6 rounds of Buffalo Bore and all 6 fired without issue.  I also ran 6+1 rounds of Critical Defense and made a single hole about 1/2" wide and 1" tall at 7 yards, a lot more accurate than the Winchester but I can shoot an entire box of "Train" through a 3" paster at 7 and 10y.

I am still a lot of rounds away from trusting it enough to carry.

To follow up my previous post after confirming the gun was reliable in normal shooting stance and grip I intentionally shot it weak hand with a limp wrist just to see if I could get it to choke and it functioned through several mags just fine. Not an exhaustive or scientific test by any means, and I have seen many semi autos choke in a limp wrist scenario ( all kinds not just poly frames) but it would appear at least in my example that it is not susceptible to malfunction with a light grip.