For years I have used Federal #100 small pistol primers, mainly for my S&W revolvers with lightened trigger actions.
Right now they seem to be hard to get, but I can find small pistol magnum Federals,
so have any of you made this swap, if so, are the magnum primers harder than the regular,
and what affect do you think it will have on a mid range 38 Special cast bullet load ?

I don't know about the hardness, but they should be safe with midrange loads.

If at all, with a Magnum primer you will see very little difference in pressure and velocity. With larger charge weights sometimes you need .1gr or .2gr less a charge to generate the same velocities. If you loads are in the middle of the charge range I wouldn't change the charge and see if the accuracy is the same. If it is you are done.

__________________
Freedom is never free!!
SWCA #3437

What difference you see is dependent to a large degree on the powder you are using. Before going farther let me qualify my remarks by saying these are based on personal experience chronographing literally thousands of rounds comparing the same load with different primers. For small handgun I use three Federal primers. These are the SP, SPM and SR, as they all have the same dimensions.

In general, my experience is that the SP F100 gives generally good consistency. Changing to the SPM F200 gives slightly higher velocity (less that 20 FPS) than the F100, while giving higher Extreme Spread (E.S.) and higher Standard Deviation (S.D.) compared to the F100. Adding the SR F205 gives velocities very similar to the F200, while giving as good or better S.D. and E.S. than the F100. The F200 gives the best consistency in velocity, not necessarily accuracy(!), of all three primer types.

With some powder types, such as HS-6, there is a significant velocity improvement with both the F200 and F205 compared to the F100.

Contrary to popular internet and gun-rag myth, with a handgun that is in good, un-altered, mechanical condition, you will not experience mis-fires when using small rifle primers in handguns! I have fired multiple thousands of small rifle primers in handguns, mostly in revolvers, over the past 55+ years, and I have never experienced a single mis-fire.

__________________
Gunsmithing since 1961

I've used mag primers in my 148g Bullseye match load for 20 years. I was loading 357 pin and jug loads at the time and just wanted to keep life simple. I use 2.7 WST just like the other guys. Never clocked it out of my Python but it goes 662 fps out of my J frame. I use federal because my Python would strike light in DA after trigger work. The Mag primers always go bang for me.

Can you find any Federal Small Pistol Match Primers?(GM100M). They cost a penny or so more a piece, but seem much softer than other brands.....

I only need a thousand, so I can't mess with online order, but my LGS has Federal SP magnum, and Federal SP Magnum Gold Medal. I just wanted to know about the hardness of the primer as all my revolvers are range guns, and they all have light hammer falls (tuned to Federal 100 primers)

I loaded up a batch (38-SPCL) with magnum primers sort of by accident. The Winchester packaging is exactly the same except for the verbiage and I hate to wear my glasses . The load was 3.6 grains BE under a Lee cast 105-grain Alox-lubed SWC. To me...I did notice a slightly higher report and seeming a slight increase in felt recoil from my snubs. I have a gaggle of magnum primers and I plan to shoot them up, since I see no severe "warnings" here in the thread against doing that. Maybe I will drop the charge a fuzz to remain on the safe side.

Magnum primers are not "harder" the cup is "thicker".

At least per a E Mail to CCI, of course Federal may be different and this will all be debated.

__________________
Still Running Against the Wind

I would have no problems using the magnums. I do however, insist that none of my firearms be primer specific...I want them all to function with ANY primer. Just me though.....

Randy

For many years I have used only Small Rifle primers for .38 Special, .357, and .38 Super, plus a few others, such as .32-20 and .30 Carbine for handgun use. Never had a problem in doing so. But I don't weaken hammer springs as some seem prone to do. Primer brand is immaterial to me.