First off I am using RBCS dies and I size the brass according to the instructions.
I have been sizing after every shoot but since I am neck sizing I will see if I can go maybe three shooting before I have to resize again (except for the neck sizing with Lee dies).

Here is my question. After the shot I notice the primers were a little flattened but no ejector marks. And I am not doing max when loading. I would say I am about .5g or a little more less than max)
However I am wondering if the resizing is the issue but I will try with a lower amount of powder.

According to Nosler's load their brass states from the bottom of the neck to base is 1.438.
I use the Hornady 'measure cartridge headspace' and my shot .223 brass is about .0002 larger than virgin laupa and Win .223 brass.

Here is what I am wondering...there is a few discussion on this but when I shoot and resize the brass it goes back to whatever my resize die is set up.
Should I be doing a little more? I see people say to resize down .0002 more but how do you know if it should be more?
When I have a already resize brass the bolt when close has very very little resistance. To me that is a crush fit but should there be no resistance at all?

Bold comment is a worthless indicator of pressure which has been discussed multiple times on here.
Shoulder bump I normally use .004 for hunting rounds for reliable feeding, nothing else. Varmint/target .002 then neck size, after 4 firings I anneal, FL size and start over.
Most if not all of my 223 loads are closer to max than yours.

First sentence is what I will focus on. You need to learn to PFL size your brass. I'll show with pictures. Here are some 7mm rem mag casings that will show you what I'm talking about. These have been sized to fit the smallest chambered 7mm rem mag I have. That way my brass works in both rifles I own in this chambering. The chambers are near identical though. Thanks Winchester!! In this picture, you can see how far down the neck the brass is sized:



The shoulder gets bumped down on this sizing process as well. I prefer about a .002-.004" bump. That can be checked with a comparator. I generally do this by feel though, as I've done this enough times that I know what type of resistance you should have on the bolt when you close it on a sized piece of brass. Here's another picture of how far off the shell holder is from the bottom of the die:


Now, if I were to set up the die set as per RCBS instructions, I would be bottoming out the die on the shell holder and oversizing the brass. This is detrimental to brass life and also precision. Also, when I look at your measurements, there is no damn way you are measuring to the exact .0002". That is 2 ten-thousandths. There is no one here telling anyone to bump it down another 2 ten-thousandths. There is also no need to be neck sizing your brass if you are just loading up hunting ammo and not competing in real competition. There are a lot of guys here thinking they need to, but in all reality, they don't. With this reloading schidt, keeping it simple and being of sound mind will go a hell of a long way..

Unless the above pictured die or shell holder have been modified, I cannot believe they are bumping the shoulder at all!

If the OP is bumping the shoulder .002 to .004 inches, I would not be concerned about his sizing procedure, or a slightly flattened primer.

If you're bumping the shoulder back .002 and it's still hard to close the bolt, your die isn't sizing the body enough.

Be sure not to confuse any firing pin cock on close resistance with a case sizing issue.

The other guys answered your question, but where you state your primers are looking a little flattened,

if you are not loading to closer to max pressure, that can also cause the primers to flatten.

I do a lot of downloads for kids use, working with BSA and also new female shooters.

I am currently developing some light loads for a campfire member's grand kids use... with Win 452 AA shot gun powder.

The load is 8.5 grains in a 223 case. It isn't very high pressure, but the primers come out flattened... yet when resizing the cases, they don't offer much resistance with the loading die, doing a F/L resize.

by the way, I support FC363s response the most.

Instead of just trying to barely size the case, I play with bullet seating depth instead to barely touch the lands. That is my preferred method.

Playing with seating depth is your preferred method of sizing cases??? This makes no sense

It’s a oregon thing…

I find this hard to follow.

Smile when you say that.




P

That is NOT what I said...I full length size a case, THEN I play with bullet seating depth...

Does THAT make sense?

If I do something, its a Virginia thing.....that is where I am from and I find my way of thinking is pretty common back there... not so much in Oregon... I live here, for less population and bigger mountains....but I am a Virginian, 17th generation... not an Oregonian...

Blind trying to lead the blind……..

Setting up the FL sizing die by the directions is generic. It needs to be set up based on fired brass from this rifle. It sounds like you have a collet die, so your set.... Fire 2 or 3 pcs of brass 3 times, and only neck size it between. Measure those 3X fired cases with your headspace gauge, and set your FL sizing die up to push the shoulder back your desired amount based on what your chamber is. IMO, the Forster FL die is a better option than a RCBS and collet deal. Concentricity is great, and your sizing the same way every time. The only thing i use collet dies for is perfectly sizing brass to neck turn.

I used a direct quote - you're now saying what you really said is not what you meant to say