Quote:
|
So what constitutes +P or +P+ loads
|
+P is clearly defined. It is going over max SAAMI pressure limits by no more than 10%. +P+ is not defined and is more of Elmer Keith territory.
Quote:
|
Does velocity have anything to do with it ?
|
No, it is based off of pressure only. Since internal ballistics and pressure can be a funny thing, you really can't safely make "+P" ammo unless you have a reliable way to measure pressure. Many experienced reloaders may make hot ammo that is likely +P because they have a good grasp and understand how far to safely go.
Quote:
|
Unlike rifle loading where it seems I'm less likely to get to max charges . I always seem to be able to get to max charge and past when loading 9mm & 45acp .
|
There are fewer pressure signs when loading straight-walled, lower pressure pistol cartridges. 9mm operates at around 35k psi (without looking it up), and 45acp at 21k psi. Meanwhile, .308 operates at 62k psi. Yes, almost triple of 45acp pressure and almost double that of 9mm pressure. It can operate at this pressure because of rifle vs handgun design (rifles rely on a mechanically locked breach, fully support the case, and surround the case with much more metal support than handguns). You see flattened primers and case stretch in rifle rounds as signs of overpressure. You do not see these same signs in pistol cartridges.
The most reliable layman pressure sign with a semi-auto straight walled pistol is how far your brass gets flung. Even that is kind of like reading tea leaves. Pistol overloading can be especially dangerous because increasing charge weight by just .2 grains with many powders in a 9mm cartridge can give you up to a 4-5% greater charge weight. Couple that with seating just a hundredth of an inch too deep and the results can be VERY bad. Internal pressure is not linear, also. A 4% overcharge in powder weight could possibly equal a 10%+ overpressure spike, depending on the characteristics of the powder.