A year or so I taught my son-in-law to reload. He has called with a question that I can't answer since I don't reload for handguns.

He took a load from a manual and used 14 gr of Alliant 2400 with a Hornady 158 gr bullet. And, he used a small pistol MAGNUM primer rather than a small pistol primer as called for.

Question: Will the use of a magnum primer be a problem and should he come over and pull the bullets and start over?

What gun? In all the data, regular pistol primers are listed for 2400 because it is not hard to ignite like some others. Going to a "mag" primer will, no doubt, raise pressure. How much? In a Smith 28 for example, I would not worry but I would fire the first few with careful observation of the fired cases. Excessive pressure. Now a Charter Arms guide gun built for light of weight...

The safest answer is to pull down the ammo. I am afraid that even as my years advance, I would pop a few to see what happens. Tha's me. luck.

Depending on who's manual you look at, & the particular rev., that load is below max. Using a mag primer will raise pressures some (3K-5K), but his load is likely fine. They may show some signs of pressure, but the gun is not going to kaboom. SHoot 6, see how they look, sticky cases, flattened primers, etc.

It's a new S&W 686 I believe. These were his first loads for it.

Thanks fredj - I expected as much as was willing to fire a couple of rounds for him; however, I wanted someone's opinion who knew a lot more about it than I do.

Per my destructive work up experiments, the difference between a small pistol primer and a magnum small pistol primer is ~ = 0.5 gr of additional powder.

If you can read between the lines on these published data, you will know how insignificant 0.5 gr of powder is, in the grand scheme of load book error.

quote:

"Speer 6" 1964 38 s&w special 160 gr. soft point 11 gr. 2400

"Speer 6" 1964 357 mag 160 gr. soft point 15 gr. 2400

Midway "Load map" 1999 357 mag Speer 160 gr. soft point 10.9 gr. 2400

What does it all mean?
The max pressure of 357 mag was reduced when thin chamber wall revolvers were introduced. The thin walls stretched easily and stretched back elastically, but the brass could not stretch so far without taking a set. The sticky brass caused the pressure rating to be reduced.

But a 686 has thick walls, and so could take more pressure than the published loads, still maintaining the margins to difficult to extract cases.

I have never found a 38 special that could not take a slow powder overloaded 158 gr load that required the brass be pounded out.
357 magnums are often thicker walled than 38 specials.

Link to 1993 post by Berkovitz on 357 mag chamber wall thickness

He can just shoot them.