Originally Posted by edge
My question is how much does the pressure change using different primers?
How much pressure difference would you expect with a load designed for a Small rifle primer and switched to a large magnum primer? Would it be significant?
As an example: if I check the Hodgdon Reloading Data Center website I find this load for a .458 Win Mag:
300 GR. BAR XFB Hodgdon H322 83.0C 2753 46,700 CUP
( CUP to PSI not exact, but it should be around 55,000 psi )
I have a strange setup.
I use smokeless powder in a custom muzzleloader.
For priming I use a modified 45 acp case with a 209 cci magnum primer
The flame path from the primer to the powder is 1.1875 inches.
I am shooting a Sabot/Bullet combination that weighs 285 grains and obviously it is already bore size since I loaded it from the muzzle.
My rationale is that this load should be safe since my projectile is 15 grains lighter and it can be loaded by hand ( with some effort ).
This is a compressed load in the Win Mag and probably 100% + in my ML.
The main difference is the primer!
I have a Pressure Trace attached to this rifle and this load ( one shot ) came close to 70,000 psi.
At this point I either need to question the PT reading, or probably need to conclude that the difference is primer related.
Thanks in advance
NEVER change primers without starting low or refering to reloading data for a starting point.
All primers have a different flame front(amount of heat ) designed for different powders and
volumes of powders, different case designs and calibres ( Bore Dia. ).
Even when you change brands of the same size primers you can run into trouble if loads are
What you are looking for in a primer is enough to ignite a given powder charge consistently
with out over doing it and causing presure to spike to fast .
Even if the projectile is lighter it is the combination of powder,primer,bore dia.,barrel length
and bullet type that effect pressure.
The sabot rounds normaly seal in the barrel faster and better than a regular projectile so
pressure can be higher than a projectile of the same weight without the sabot.
Some reloaders have found that going from a mag primer to a standard primer improves
performance on some cartriges.
Also different primers have different cup thicknesses and can be pierced in weapons designed
for higher presures and firing pin strikes. (Not Good ).
There are primer burn rate/heat charts that you should look at and see the difference from
one primer to another and help you deside which to use.
I hope this helped
J E CUSTOM