I am using a Lee Zip Trim for my first batch of .223 and when I installed the case length gauge it fit nice and tight up to the cutting head but when I began trimming it was trimming the case down to 1.758. It was very consistent it just seemed a little long. Should I file down the gauge or is it ok where it is?

Beware of the diameter of the flash holes. The case length gauge has the nipple on the end that goes through the flash hole. If it doesnt go through the hole all the way or in an inconsistant manner, you will get long cases or different lengths.  I quit using mine because of this issue.

Leave it, its under max, with time the gauge will wear a divet in the holder and possibly material from the gauge itself so your trim length will eventually become shorter, no sense accelerating the process. For safety under max is good, for accuracy consistency is key.

This is the first one I saw that was cutting long but it is under max and consistent and that is what's most important. Still that does not seem right.

The stop and the length pin are both very hard and don't ware. I have found that the cutter actually cuts into the back of the rod when you tighten it and eventually will start to trim shorter.

Mine is down to 1.743" and I am going to replace it.

Make sure your length rod is seated good and as the other reply suggested make sure the pin is fitting through your flash holes correctly.

Well it defiantly is consistent. Out of my first 200 cases i didn't have anything over +/- 0.002 and most of the cases where dead on at 1.758

 

Sounds like you got it under control. Lee's quality control is not always top notch. The only drawback you may have is the need to trim more often but some guys prefer to trim every time anyway. I don't crimp any of my AR ammo, taper or roll, so as long as they are under max that is all I'm concerned about.

The Lee cutter is consistent but has it's limitations. I have made a few tools that use their cutter,stud and length rod in an attempt to speed the process. I even made a lathe type trimmer that uses them. The problem is the rod through the case mouth. This set up has to be non rigid to allow for misalignment. If it is rigid the inherent wobble will cause the rod to open up the case mouth.

I have two cutter heads and there is a bit of variation with them. One trims to 1.750 and the other to 1.752. You can try to thread the shaft further onto the cutter to reduce the trim length.