Need help "reading" .223 primers...

Finally taking my first steps into rifle reloading. Trying to work up a load with a Hornady 75gr bullet for my AR. I've been reloading pistols for about a year, but tend to run those at low pressure for the caliber. Now I'm looking for a load to shoot 400yd and don't want to have to fight the wind more than I have to, so just loading enough powder to cycle the action won't cut it anymore.

Anyways, following book recipes but the primers are looking a bit flattened to me in comparison to what I'm used to... The load is Federal brass, CCI SR primer, Hornady 75gr BTHP seated to 2.26" and from 23.5-25.0gr of Varget, working up 0.5gr at a time from left to right. I do see a bit of cratering on the 25.0gr load, but they all have squared off the shoulder of the primer compared to before firing, is this OK/how much is OK? Unfortunately, had chrono problems so no velocity data... I also attached a pic of how factory Hornady 75gr TAP FPD leaves the primers in the same rifle for comparison.

Just looking at primers---I'd call 24.5 gr my max load.

IME-most all my primers have squared shoulders when fired in ARs. When the metal starts "flowing" and filling the gaps in the bolt face, leaving a "crater wall" around the firing pin indentation etc, it's time to call a timeout :scrutiny: and back off your loads a bit.

some cratering, looks like a max load, which is fine. Shoulders are still round. Either leave it, or back off half a grain. I'd backoff, but mostly to go easier on the brass. Some day you might get bad primers which might pierce and etch your bolt face too.

edfardos

24.1 - 24.3 is widely considered the std max load in HP competition using 75 or 77 grain bullets at mag length. I'd also be using CCI #41, Rem 7 1/2 or Wolf SRM/556 primers for the harder cup they offer.
/B

ahhh..... handloads in an auto-loader , what fun , your best bet is to use a chrono, reading primers is a myth , from one brand or even from one batch to another they will not look the same. do to how thick they are, or how tight the went in , if your head space is off from one round to another letting them slam back harder than the one before it , another trick that is better than trying to read primers it to mic. the base of the case. however this will grow after a few fireings. best to check with new brass as you work up your loads. and that still may let you get your loads too hot! if your brass is thick or hard you cloud be too hot befor the case head starts to expand , but since you already ran some loads that you think are at the max , check them with a mic. and see if the cases are growing , starting with your light loads and working up from there , again trying too read primers for high PSI realy don't work, I have had flat primers with light loads eather because they were thin , or maybe loose or had the shoulder pushed back too far

They look fine, but looks can be deceiving. What kind of velocities? There is no free lunch.

Primer reading is a myth

Primer appearance has as much or more to do with factors involving the rifle than it does the load.

http://i3.photobucket.com/albums/y96/krochus/FIRE/Casehead-2.jpg

As you can see from the pic you can in fact be grossly overpressure and yet still have a "correct" looking primer.

Leave the primer guessing to the more superstitious handloaders. All any of us can really do is stay within published data and watch what our chrony is telling us

24.1 - 24.3 is widely considered the std max load in HP competition using 75 or 77 grain bullets at mag length. I'd also be using CCI #41, Rem 7 1/2 or Wolf SRM/556 primers for the harder cup they offer.
/B

Interesting. Hodgdon lists 25gr as the max on their website. Why the discrepancy?

I may look into the CCI military primers in the future though.

I totally agree about using a chrono. Mine had an unfortunate encounter with a piece of supersonic metal though :uhoh: Honestly, compared to pistol loads, even the factory loads look flattened (somehow they look flatter in person than the pics). Guess rifles just work at much higher pressure levels...

I like to use the 270 7x57 analogy

Same piece of brass (head) same primers

If 270 doesn't show you pressure signs at 65k psi why would you expect those same primers to tell you when you're over 51k psi in a 7x57

CCI 400 = cratering. Thin cups.