Thread: Primer power?
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Old 12-02-2021, 09:38 PM
Tu_S Tu_S is offline
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Quote:
Originally Posted by glowe View Post
I am in the unfortunate position of not having any small pistol primers available, so set out to duplicate my standard velocities by using small rifle primers. I loaded with both pistol and rifle primers and consistently found that I gained around 50 fps with small rifle primers. I can now confidently load my 38s using small rifle primers until the market resupplies SPPs. This equated to about a 7% increase in velocities for the loads I tested. Another data point I noticed is that the small rifle primer recorded a lower standard deviation than small pistol primers, which is certainly a good thing.

Owning a chronograph is essential for this type of load development and I would not hesitate to try primer substitution by loading both primers and check velocities at the range. Start out loading about 10% less powder and check the magnum primer velocities, comparing them to your standard primer load velocities. Load rounds in groups of 5, slowly stepping up to standard amounts of powder with magnum primers and stop testing when you reach the proper velocities to match those using standard rifle primers. Pull the bullets on the rest. Same testing can be done with military primers and you can develop loads that match velocities and are perfectly safe substituting the different primers.
Curious to know, what powder did you use for this test?

Among the theories I have heard, if you're using a fast burning propellant like 700-x, you won't see a big change moving from a standard to magnum primer since even though it is a magnum (or in your case rifle,) the powder burns so fast it doesn't matter. Now if you go to something slower like CFE Pistol, initiating more of the charge when it starts will cause the rest of it to burn up faster than it normally would, and you would see an increase in pressure.

I have to say I have no idea if this is true or not. I guess I'm over educated enough to make myself dangerous and can see how it makes sense, but am also old enough to know I don't know everything and have no problem admitting it.

So, I guess I'm asking to either get another data point to say it's a viable theory in the case of you using something on the slow side, or have more information to bust it.