How much difference does small pistol mag primers make?

[Southerngunner]

I picked up 2 cartons of Winchester primers at gun show this weekend and the small pistol that I thought was standard or magnum, one carton turned out to be just Magnum I did not check before I got home and didn't want to travel 120 miles round trip to exchange them. I could use them for 357Mag loads but almost all of my small pistol loading is for 38 spc. & 9mm. I use Red Dot, Titegroup, 231, or Unique and I only shoot cast slugs at medium velocities. Either way I plan on keeping them but I was wondering if I can use them without building too much pressure with the same powder charge in 38s. Any help?

[km101]

I have not found that magnum small pistol primers make a difference in moderate loads. I have not chronographed them, but I have shot identical loads (except for the primer difference) and there was not a noticeable difference in recoil, muzzle blast or point of impact. I shot them in .38spl and .357mag loads. I alternated the loads in the revolver cylinder.

I really don't think they will make a difference in anything but near max loads. I would not use them in anything approaching max book load unless a magnum primer is called for.

YMMV

[pworley1]

I do not think you will be able to tell any difference unless you shoot maximum loads. I am not sure that you would even tell a difference with maximum loads, but I would not recommend it.

[Zymurgy50]

Got a rifle that uses small primers???
The magnum pistol is exactly the same as the standard small rifle.

[Petrol & Powder]

Unless you are near max loads, you'll never know. I've used 10K + and it doesn't make a difference. Back when I had access to a chronograph, I shot loads that where identical except for the primers. The only observed difference was less shot to shot velocity deviation but no increased corresponding accuracy changes.
Some people say the primer cups on magnum primers are harder, they may be, I don't know. I actually prefer mag primers with some very light loads in an effort to obtain consistent ignition.
I would be careful if you are approaching, or at maximum loads.