Got out and put 150 rds thru my new FS 320 today. Really sweet and smooth shooting gun. Just had a few issues to ask about. I shot 100 rds of Rem. UMC,115 gr with one stove pipe on the last shot from one mag., 1 failure of the slide lock after the last shot and problems with spent casing ejecting when I was loaded with 17+1. Also had a failure to close to full battery twice with 17 rds in the mag. The 50 rds of Perfecta shot great just not as accurate. Will these problems work their way out with more rds put thru the gun or should I look for other solutions. Any help will be greatly appreciated since this is the first FS 9mm I have ever owned. I have never had any of these issues with my M&P 9c but it is much smaller and lighter so I know I have to get used to the larger, heavier gun.

I'd give it a good 500 rounds before you worry too much. My 320-X5 was tight and had to be pushed into battery, after 500 or so rounds its been 100% reliable.

UMC is garbage.

Concur with the break-in. I have a P320FS .40 and a P320C 9mm, both purchased in January 2015.

The nine ran 100% with Rem-UMC 115gr ball. The ammo, however, was purchased in 2006, well before all the Sandy Hook madness. Still running through the 5,000 rounds I bought at $5.00 a box. I can't speak to current Rem-UMC quality, but don't doubt PASig. Winchester White Box (WWB) also pops up frequently with QC issues.

The .40 had failures to chamber about one every two mags. Just shot it. It went 100% reliable in about 300-400 rounds.

Contrary to popular belief, break-in periods are still required with some handguns. Forget precision NC techniques. They are mass produced products with min-max tolerances. It is not limited to specific manufacturers or models. It is a random happening whether the specific gun you buy needs or does not need a break-in period. Jeez, you have some Hi-Points that run 100% out of the box.

The obvious rule of thumb that you are experiencing is: If problems occur with one ammo brand but not others, it's the AMMO. Even that might clear up after break-in. Just keep shooting.

FWIW, my nine runs Rem-UMC, my own reloads and Rem 115gr +P+ (BPLE) with total reliability. What does this mean? Nothing actually, other than my gun is reliable.

P.S. You may want to load up your mags to full capacity when not in use. After a couple of weeks they will be easier to load. In some cases it may improve any first round feed problems as well.

I have 2 Italian and 2 US made mags. The US made ones are noticably stiffer. If the mags are US, the springs might need to take a set. I haven't had them drag enough to cause a failure but they do exert some pressure on the slide.

Mark the mags and track which one(s) failures occur with and try other ammo too.

ETA: failure to lock back is user riding the slide stop 95-99% of the time. Not to say it can't be ammo or firearm related, just not usually.

I have owned several P 320 compacts. Had no issues after a few hundred rounds thru each one.I am one of those grease freaks. Lucas red wheel bearing grease or Permatex white lithium. I use a lot. I like to see it dripping out when the gun is warmed up. Normal operation throws the grease all around the operating parts. After things are worn in a bit all operation improves. I did learn to number my mags to help isolate any feeding issue or first/last round flyers. Currently I only have a P320-45. Have a Gray Guns fat guide rod and a 12LB recoil spring in it. Shoots any reload or mild factory ammo I feed it. A whole lot of fun,accurate and minimal muzzle flip.

I've fed my 320 compact lots of cheap ammo, including steel and aluminum cased rounds and I haven't had a single issue.