Thoughts on why Fed magnum primers caused lower ave speed than S&B SPP primers?

[Dan_69GTX]

I was reloading 9mm Berry's 147 RN plated bullets using TiteGroup powder when I received my Natchez order.  I substituted 10 Fed magnum primers for the S&B small pistol primers to see what would happen. 

So I took 10 loads before the Fed primers, and 5 after just to compare.

10 shots - S&B primers - ave 942.2 FPS
10 shots - Fed magnum primers - ave 925.2 FPS
5 shots - S&B primers - ave 950.3 FPS

Any idea why the Fed primers would cause a slower ave speed?

[ReloaderFred]

Changing any component will affect the outcome, including primers.  Handloader Magazine has done several articles over the years about how different primers affect velocities, and even accuracy, primarily in rifle loads, but it also affects handgun loads as well. 

In primers, things that affect powder burn are the length of the flame, the brisance (speed) of the flame, and the length of time of the explosion of the priming compound.  Whole books have been written on this subject, but suffice it to say, any time you change a component, it's going to change the results.

Hope this helps.

Fred

[IDescribe]

I was reloading 9mm Berry's 147 RN plated bullets using TiteGroup powder when I received my Natchez order.  I substituted 10 Fed magnum primers for the S&B small pistol primers to see what would happen. 

To be clear, are you saying that the 25 rounds tested came from the same run, and you just slipped in 10 Fed Mag SPP?  Or were they loaded at different times?

[Dan_69GTX]

To be clear, are you saying that the 25 rounds tested came from the same run, and you just slipped in 10 Fed Mag SPP?

That is correct.  All the same manufacture brass too.  I just picked out the 10 before and 5 after I added the Federal primers - out of about 100 loaded total.

[M1A4ME]

Doesn't really make sense to me either.

"Magnum", in my head means hotter.  Itsn't that the idea?  Meant to ignite, reliably, more powder, or powder that is a little harder to ignite.

I distinctly remember reading, many years ago and mulitiple times, that magnum primers would increase pressure and if you switched to magnum primers you should reduce powder charges and work your load up again. 

"Increased pressure" usually also means higher velocity.  People (reloaders, especially new/inexperienced ones) are usually the worst for trying to get the highest possible velocity and causing themselves problems with their guns.

For me, it just doesn't compute.  You might try it with a different powder to see if it's just something about that particular powder.

[jameslovesjammie]

Think of magnum primers like high octane fuel: if your application doesn't warrant it, it won't burn efficiently and performance will suffer.  Titegroup is a fast powder in a small combustion chamber and doesn't require a magnum primer, so it doesn't burn as efficiently as a standard primer.

If you flip the situation, say H110 in a .357 Magnum, you have a slow ball powder in a large combustion chamber.  This application will burn more efficiently with a magnum primer than a standard primer.  But switch to a faster flake, like Unique, and you will be more efficient with a standard primer.

It's all about matching the proper components together for the optimization of the load.

[Dan_69GTX]

Interesting analogy.

The only reason I did this was to test/learn.  Now I'm even more curious.  Next time I'm loading some hp-38/231 loads I'll substitute some Fed Mag primers and see what happens to speeds.  I'll try it with my "powder puff" loads that my wife and Dad shoot and some mid-range loads too.