Primer signs...
Am I wrong to assume that shorter barrels are not getting full burn thus lowering pressure?
Yes, this is an incorrect assumption.
If so should I raise the powder 0.1gr until I see signs of pressure just to see how high I can get velocity out of my short barrel?
Nichts! Nein!, und HELL NO!!!!!
I confess,I do look at my primers.I'm looking for caution lights and stop lights.
So do I.
Something to consider.Most of the "signs" apply to centerfire rifles of bolt action strength operating safely at 50,000 to 65,000 psi.
Its a bad plan to apply those same signs to an 1873 Win lever action or a 30-40 Krag with a single locking lug and 1898 steel.
I disagree. It's a bad plan to disregard pressure signs, and much more important in some guns, than others.
You read flattened primers and you may get a bolt through your cheekbone.
You read flattened primers WRONG and you may get a bolt in the face...
Reading primers is a bad idea.
again, reading primers wrong (making incorrect conclusions) is a bad idea.
The same primer is used in a 45acp and a 10mm auto. Max Saami pressure of a 10mm is almost double that of a 45cap. If you are flattening the same primer in a .45 that goes in a 10, what does that tell you?
It tells me not to consider different things as identical, because they share some common components.
OK, yes reading primer signs is like reading tea leaves. The only consistent and reliable information tea leaves give you is that somebody drank the tea.
The only thing flattened or cratered primers tell you with absolute certainty is that something undesired is going on. The most likely cause is higher than expected pressure. But its not the only possible cause.
Primer pressure signs are not a calibrated thing. And, they cannot be, so don't think of them like that. There is no "primer A flattens at 32K psi.." because while it might, it also might not.
EVERY GUN AND AMMO COMBINATION CAN BE DIFFERENT.
There are a huge number of factors about the gun, the ammo, and their fit together that affect pressure signs on primers (and cases).
The exact same ammo that craters primers in gun A may not crater primers in gun B. And it may be well within the SAAMI listed specs as "safe". Or it could be outside them. The primer won't tell you which. All it tells you is "I'm not happy about something".
When you get a pressure sign, like a flattened primer it doesn't matter (much) what the actual pressure number is, what matters is that for that particular gun, with that specific combination of load components, you go no further.
What the "book" data says a max load is, is the max load they reached with the firearm and components they tested. While its usually very similar, the safe max load in your gun or mine with our different components can be significantly different.
