I'm new to rifle reloading but not pistol. I bought .223 dies and had some brass so I sized 10 pcs. THEN, my Lyman case gauge came and I used the case gauge to adjust the resizing die so the case is within the min/max for headspace. But I used the gauge on the 10 pcs previously sized and the cases are 0.002-0.003 below the min surface of the die. These will be eventually shot with 55gr plinking rounds in a AR. CAn I use those 10pcs of brass? Thanks.

If you set up the sizing die correctly according to the instructions the first time they should be just fine. .003" should not be any problem, I doubt if all factory ammo is within this spec.

__________________
H Richard
SWCA1967 SWHF244

Be sure to check that the resized brass fits your rifles chamber.
In more than one instance the round fit the "case gauge" but would not chamber in the rifle...it can happen.

Back in the day BCG , before case gauges , we used our rifles chamber as the gauge !
Gary

I use the Hornady cartridge case headspace gauge and measure a fired case and then bump the shoulder back approximately .003. The problem with drop in case gauges is a fired case will not go all the way into the gauge. Meaning you do not know how long a fired case is to set the die up.

Another problem is the AR15 can chew up the case rim and the ding in the rim has to be filed down for it to drop into the gauge.

We live in a plus and minus manufacturing world and chambers and dies vary in size. Example I have a Lee .223 full length die and if it is setup per the directions it will push the shoulder back .009 shorter than the chamber.

Bottom line I'm 67 and it is easier to see a digital vernier caliper than straining my eyes looking at the two steps in a drop in case gauge.

NOTE, Lake City brass is made harder in the base than .223 brass and you can buy once fired brass very cheaply.

.223/5.56 - Cleaned, Deprimed & Swaged - LC Only - 500 Pieces $59.00
.223/5.56 Cleaned, Deprimed & Swaged Lake City Brass 500 Pieces

If I am reading your question correctly you have the shoulder of the cases set back just a bit too much. If that is the case the only issue from using these 10 rounds is that the case life for those 10 cases may be reduced by 2 or 3 loading cycles at most. In addition you'll see a bit more case stretch than normal in that firing, so check the overall length and trim the cases after doing a full length sizing on them.

BTW, I trim my rifle cases to 0.002-0.003 inch under the Median length specification. By doing this I can get a few more firing cycles in before I have to trim the cases again. I also like to run the gage length as close to 0.003 inch under the maximum as I can get the dies adjusted to. In some rifles this could present a chambering problem with "tight" chambers but in my case both of my 223 rifles are chambered for 223 Wylde and were precision reamed so I have no problems with a "tight bolt". The reason for sizing a bit long is also to help minimize the need to trim cases and doing this also helps extend case life. Note, one way to test if you are sizing your cases "too long" is by making up a dummy and loading it into the chamber by dropping the bolt. If you can extract that case normally then you aren't "too long". If you have to mortor the rifle or struggle a bit to free that case you should shorten your length be about 0.003 inch and test again. Finally I'll note that most commercial rifles today have chambers that are sized "long" to insure function with even really cheap budget ammo with questionable adherence to the specifications for the 223.

Also, measure your Lyman case gauge. I have one for .223....and it is actually too short. The "max" case length step is about right, but not quite 1.760"....but the "min." is way shorter than 1.750".

Before I checked the gauge (I simply assumed it was right)...it caused me to cut some cases a good bit short. Measuring the gauge revealed the problem.

I just went back to using my calipers for checking case lengths.

When starting a new loading procedure for a rifle cartridge which requires set up of the dies, I have always had that rifle right there waiting to be used as my 'case gauge' for that loading. The first completed cartridge gets degreased and the bullet and shoulder area is coated with Dykem. It is then chambered with the safety in the on position if possible. The cartridge is then extracted and examined for telltail marks. If everything is good I proceed to reload that batch. If not the appropriate die is adjusted and another cartridge is loaded and tried. Always remember to keep the rifle pointed in a direction that would minimize damage if a ND should occur. ......