Hello,
I will be hand loading for a .223 Service Rifle w/ a wydle chamber. I purchased new brass, fired it once and have taken a case measurement with the Redding Instant Indicator Headspace gauge. When setting up my full length resizing die how far back from the fire formed case headspace measurement should I set my resize die? Or should I set it back at all?
Thanks

I set them back. 001" - .002", they must go into the chamber and allow the bolt to close, everytime!
Doug

Set the shoulder back the same for Wylde or 5.56 AR chambers. Most recommended to set the shoulders back .003"-.004" for reliable cycling in AR's. I aim to get .003" but due to springback they may be .002-.004". Main difference between 5.56 and Wylde chambers is the leade or throat. Don't think you'll see any accuracy improvement and maybe failures to chamber trying to have very little case clearance.

Never thought of resizing fired brass to closely match chamber dimensions for accuracy sake, but rather to extend case life. See some who have shoulder of the case back several thousands and naturally when fired the case will grow to match the chamber, it's call case stretch if you will. Some few thousands as mentioned is a good approach and will extend case life. If you keep bending a piece of wire for example, it will eventually break whereas a brass case stretching after numerous rounds will separate usually about 1/3rd. from the base.

The JP gauge below is cut with a Wylde chamber finish reamer so it not only checks head space but also case diameter.

Semi-auto rifles should have the shoulder bumped back .003 to .006 and the case diameter should be .003 to .005 smaller than it fired size. These dimensions are recommended for reliable feeding and extraction.

JP Case Gauges

Any rifle with a tight chamber is going to suffer with out-of-spec ammunition, and most operational failures in self-loading rifles can be traced back to this problem. If you're a reloader, you know this better than most. Unlike other gauges available, the precision JP Case Gauge is cut with an actual match chamber finish reamer so it not only checks head space but also case diameter relative to typical match-grade chambers and min/max case length on top of that. What's more, the fact is that most other gauges indicate minimum and maximum case headspace as defined by SAAMI, which still allows for a possible interference between a maximum-sized cartridge and a minimum allowable chamber. While this would not be an issue in a bolt gun, it will bring everything to a stop in a self-loader. Our gauge insures that the maximum cartridge indicated by the gage is still within the minimum SAAMI allowable chamber. In other words, if your ammunition passes our gauge, it absolutely will fit the chamber. It's the only sure way to know that your ammo is compatible.

https://www.jprifles.com/1.5.1.2_maint.php

I use the JP gauge to check the sized cases and also again checking the loaded rounds.