What adjustment should I make using wspm instead if wsp primers in 9mm and 40 sw

[right winger]

Hello,
I just got a good deal on a few thousand win small pistol mag primers and would like to use them in 9mm and 40sw along with my 357 mag. I usually use WSF powder in both - 9mm load is 115 fmj with 5.5 grs and wsp. 40sw load is 6.3 grs with a 165 gr xtreme tc and a wsp. How much should I adjust for the use of a magnum primer? Thank you for your input.

 

[ArchAngelCD]

Usually the difference will be .1gr or .2gr and see how it goes. Since your 9mm is .2gr off the max dropping back another .2gr and look at the results should be fine. The lawyer answer is to drop back to the starting charge and work back up.

The same seems true for your 40S&W load.

 

[Blue68f100]

I know some people use them but I would be concern about the primer dislodging the bullet before the powder built up pressure to burn properly on 9mm and 40cal. The 357 should be fine since it's a much larger case. I would back off a min of 0.2gr on the 9mm and 40cal if your at or near max load. Have not used WSF in 357 mag. It has a much larger case so it should not be a problem unless your running full tilt magnum loads.

If you have a crony use it. If this is happening it will show up as scatter, Larger than normal ES & SD.

 

[right winger]

Hello,
To clarify I am only using the WSF in my 9 and 40 rounds. I use 2400 and 296 in my 357 loads but with magnum primers. I just have many more magnum primers than I need and would like to use some in the above rounds if possible. Thanks for your help and guidance so far. I appreciate your expertise.

 

[Rule3]

The "correct" answer would be to use the start load when changing any component.

With 9mm there is also +P data so I would not worry to much about the Mag Primer if you start low and work up.

Heck there is no real data or actual, verified data showing the difference in pressure between using a regular primer and a Mag primer. Plus all brands of primers are different.

How is it than Winchester can have a Large Pistol Primer that is good for regular and Mag loads?

 

[rfwobbly]

I did testing with 3 different brands of primers in 9mm ammo some time ago for another board. At the Minor PF (plinking) velocities of these tests (all around 1040fps), there was no real difference between standard primers and mag primers. Over a chrono, I saw only 3-5fps difference in those low velocity ranges.

No doubt that as the loads increase, the effect of mag primers would/could become more pronounced. So your answer depends upon your load. Therefore I have to agree with ArchAngelCD.

 

[Walkalong]

I agree with everyone else to back off a little. Maybe .2 Grains, check recoil, how far the brass ejects, velocity, and work up or down as needed.

I did a little non scientific primer test in 9MM. I do not have any small pistol mag primers, but I did include some small rifle primers in the test.

As rfwobbly found in his test, the numbers were not that far off from each other.

I did not look up your charge, but if you are not at max there is unlikely to be an issue, but dropping back a couple of tenths and checking first is always a good idea.