How To Judge Pressure In The Case, Not Only Looking At Primers.

[TORSTEIN]

When you work enough with your gun/cartridge combination, looking at primers is ok. This in conjunction with measuring the " pressure ring", will let you know where you are, pressure wise.
This method can not be compared to psi, lup, cup or pascal readings. But it will be an indicator & the reference is a factory round. Take some factory rounds and fire them in your favorite gun. What you now have is some cases having a pressure ring close to, or slightly below the industry standard for max pressure. What is happening when you fire the round is that the case expand and then contract. But not at the same rate all over the case. The base/web/head is stronger than the rest of the case, an it do not expand(that much).
In the translation between the web and the rest of the case it forms a "ring". You will be able to see and feel it. It is not(the pressure ring) even all the way around the case, because the case rest at the bottom of your rifles chamber. There is more air space above it. It is easier to expand that way. Therefore the pressure ring is larger at one point. Take your fired factory round and mike it(a micrometer is a must here).
Slide the micrometer down the case until you find the pressure ring, if you do not see the ring with your eyes. Most often the ring is shiny. TURN THE CASE AROUND WITH YOUR FINGERS AS YOU MIKE IT(LOOK AT PHOTOS). With a little practice you catch the high spot.
Make a note of the measurement.
Take the same fired rounds & divide it by the numbers of rounds(ex. 5). This is the averange measurement.
Take the same fired cases. Load it up and have fun.
Measure again and it will show where you are compared to a factory round.
If lower, keep adding powder. If above, reduce load.
Do as I say, not as I do. He he.
Sometimes I load to a pressure above a factory round.(Different makers have different max loads!!!).
Question asked??? When is enough, enough???
Example taken from Bushmaster v-match 20" in 223.
Factory PMC with 55gr bullet give me a pressure ring of 9.550mm to 9,555mm(Today all of my measurements is in millimetre. Divide by 25,4 to get inch).
A "healthy" load of 55gr Hornady v-max bullet in the same case give me:
POWDER: Vihtavuori V-N 133.
23.2gr give a pressure ring of 9.550mm.
24.0gr give a pressure ring of 9.570mm.
25.0gr give a pressure ring of 9.575mm.
26.0gr give a pressure ring of 6.625mm.

I have found that the case "grow" slow as I add powder. At one point the mesaurement will make "a larger jump".
THEN IT IS ENOUGH!!!
Another parameter is f/s, if you chronograph the loads. It will also make "a large jump".
Look at difference between 25.0gr & 26.0gr of powder.
At 26.0gr the primers looks ok(it is not like for the 23.2gr load, but still ok).The case head (primer side) have marks after the extractor/ejector.
THIS IS A SURE OVERLOAD SIGN IN AR 15`S!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
As you increase the load, the pressure ring moves toward the base/web/head. I have not found it to be a way to indicate something, other than pressure is going one way & that is up.
As a sidenote: Federal 223 cases is "a lot softer" than anything else I have tried. It will blow primers (out of the case and into your AR`s trigger compartment. Gess what?? If unlucky, it fucks your belowed trigger. No good for sleep) before all other cases.
Federal primers also tends to be soft. Pierced primers before others.
Am I saying Federal is shit??? Not at all. Make a note of it instead.
After all of my writing, what is the conclution???
THIS IS A SURE WAY TO COMPARE YOUR HOME BREW LOADS TO FACTORY ROUNDS. PERIOD!
It also tells pressure between powder types and different bullets. Change one component at a time. It will make you more happy.
Now what??? I have a 300 whisper & no factory round(except corbon).
True enough. Look for extractor/ejector marks & primers.
And use pressure ring as an indicator. When you make a note for each of your loads, you will recognize a pattern. Use them in the future.

Sometimes, not always, sometimes you increase the load a little, but the pressure ring stays the same, or get smaller. What a fuck?? Do not use that specific case. It is harder, the web/head thickness vary, or the internal volum is larger than the other cases used in test. Or something spooky is going on. Whatever, take one new case. And.... you are on the road again my friend.

Some last words:
PRESSURE RING IS FOR THE SPECIFIC CHAMBER OF THAT RIFLE ONLY.
Do not monkey with that.
Pressure ring is best compared between same case manufacturer/lot. But I can see that if you use other brands of cases, it may/or may not vary.

Also look at may post reply to: MAX SPEED WITH 110GR BULLET, there is something related to this words also.

Good reloading.