Help me understand...

[BigMoneyGrip]

Friday night, I loaded some 9mm to try a new powder (Shooters World Auto Pistol, which I LOVE). I loaded 10 rounds each of 5 charge weights using standard and magnum powders.

On the lower charges, the magnum primer was actually about 25fps slower but had a much smaller ES and SD. Normally, I would think that the magnum primer would be a little faster than a standard primer, although I have read that there is no difference between the two. After I got closer to my top charge, there was very little difference in velocity between the two, but the magnum primer maintained the smaller ES and SD.

I was expecting a little more velocity out of the magnum primer and never thought about more consistent velocities. I learned something after loading for many years! Try that powder if you're looking for something new. I've never had a powder that metered so consistent or easy.

 

[GB]

My answer is not based on any real science just my perception of what I think the difference between Mag and regular primers.

Magnum primers as supposed to burn hotter. This is for better ignition of some powders in some conditions. Because the powder ignites with more speed/consistency there may be a change in the peak pressure and where that peak occurs in the firing cycle. With the small charge used in most semi-auto pistol cartridges, the change in peak pressure may not equal higher velocity but, as you have seen, with the powder you are using it is providing consistency and therefore less deviation. This is a good thing. More importantly, it should, under ideal conditions, provide a more accurate load. But as we know, what should happen and what really happens are not always consistent. The real story gets told when you measure the group size. Thanks for the incite with your loading experience. I found it an interesting exercise.

 

[fredj338]

I find magnum primes offer highe vel/pressures with slower powders. Using fast burners @ well under max loads, not much change in vel. Go to medium slower burning powders, you will see an increase in vel, thus pressures. There is definitely a diff between std & mag primers.

 

[Nevada Ed]

I loaded the Speer 124gr Gold Dot in a 3.5 and 5" 9mm pistol with
Standard and Mag CCi as well as std. Win. and Federal Gold Medal primers.
Things were pretty average at the medium loadings but at the top end
with four well known high vel. powders flake and Ball, there were
large ES spreads, group sizes and even failures to feed or eject
with the correct OAL for this bullet.

A lot depends on the weapon used..........
as to what primers work best.