Honestly - eliminate the Remington ammo and try it again. I have seen a LOT of complaints about malfunctioning semi autos of various makes over the past year - using Remington ammo. Their target ammo is under powered. One guy even paid a local gunsmith to solve the issue instead of paying to ship his pistol back to the factory. The diagnosis - the UMC ammo.

It may not be that. But I'd clean and lube the gun, and try a different brand of target ammo

As stated previously, you are probably using underpowered loads for the new return springs. This issue has come up frequently on the FN forum (FN PS90 FN SCAR FN FS2000 FN FiveseveN 5.7x28mm FNP :: FN Forum.NET) and the general solution has been one of two options.

1) Go with a higher powered load such as WWB or some good SD ammunition for about the first 500 rounds, before trying Remington UMC. The return spring should loosen up and work with all ammunition.

2) Lock the slide back on your unloaded pistol and put it away for about a week. Occasionally take the gun out and work the action and put it back away with the slide locked back. After about a week, the return spring should be loosened up enough to shoot just about anything.

I actually went with a mix of the two options. I shoot fairly warm reloads (I reload my own, not someone else's) and I worked the slide a couple hundred times and put it up for a few days with the slide locked back - haven't had an FTF or FTE yet.

Good luck. The gang over on FNforum.net will be happy to advise.

Thanks for the quick replies!
I will be interested in hearing back from the dealer on their recommendations. Virginia Arms is a great dealer and I am confident they will get to the bottom of it. One of the first things they commented on was the UMC ammo. It's also possible I am just not cleaning the barrel well enough where the chamber ends and the barrel begins. (Then when the round is fired, the casing "sticks" in the chamber and the extractor can't pull it out.) I have been just shoving the brass brush and patches in and out, and been afraid to turn the brush inside the chamber. What's the best way to get that area of the chamber clean?

It could be the ammo, limp wristing, having your support hand interfere with the action, a weak extractor, a dirty chamber or a burr in the chamber. Do the brass casings have any indentations or scratch marks on the sides? To check for a burr in the chamber, us a dry cotton swab and wipe the chamber area. Do you feel anything rough or did anything catch part of the cotton swab? Are there any cotton fibers in the chamber or barrel? Clean the chamber and barrel completely to make sure no cotton fibers are present.

I have a good grip and straight arm when I shoot. I went through at least four boxes and at least two brands of each FMJ and HP with no problems whatsoever. I was using a box of Remington UMC when I started seeing the problem. But then when I went back to American Eagle and Speer, they started jamming too. Thanks for suggesting a burr, but No, casings are clean...don't think its a burr. The dealer didn't think the extractor was weak, but that is still possible.

I am leaning towards a chamber issue, either insufficient cleaning, being gummed up at the edge of the barrel, or something like that.

But let me ask one other question: I use a small amount of gun grease on the slide where it rides on the frame. Could that cause it? (It worked fine for the previous 100 rounds)
Thanks,

I use a high temp synthetic grease for my semi-autos. I would suggest a thorough cleaning of the entire firearm (chamber, barrel - inside and out, slide, rails and frame) and look for any scuff marks, wear marks, burrs etc. Then relubricate and see what happens.

I have a brand new FNX9 that I bought for my wife for her birthday. I took it to the range with a box of remington UMC and right off the batt started having issues. A friend of mine was there with his wife and her FNX got some winchester ammo from him and flawless. With the remington you can feel it is real light on powder compared with the winchester. Bottom line I am definitely staying away from remington ammo in the future.