Primer Changes - Load Sensitivity

[yoda4x4]

So I'm looking into reloading and am curious how sensitive a load is and it's associated accuracy when it comes to changes to the primer. And specifically, just from one brand to another using the same type? EXAMPLE: Switch from Federal Gold Medal Match large rifle primers to CCI large rifle primers.

David

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[charlie b]

Very little change depending on how precise your loading is.

I do not change load when changing brands or going from std to match primers. I have seen some testing where a change in brand would give 50fps change in velocity.

[darkker]

I'm pretty much in Charlie's camp.
I haven't pressure tested any Federals, which are a simple priming compound, but have done just about all else.

CCI, Win, Wolf, don't seem to matter. Have swapped between Rem, CCI, and Win in a 204, and for load purposes it didn't matter, although you could see a difference (in the Trace only) with the ignition curve.

A side note to remember. While powders tend to take the blame for being "sensitive", it's a change in primer output that affects the ignition most of the time.

Cheers

[Fuj']

CCI, Win, Wolf, don't seem to matter. Have swapped between Rem, CCI, and Win in a 204, and for load purposes it didn't matter, although you could see a difference (in the Trace only) with the ignition curve.Cheers

I'll push on this a bit further. With this SA284 wild cat I developed,
past 8 months has had me going thru 6 different powders, but only
2 primers; the CCI BR2 and the Winchester (WLR) The barrel is at
1300 rounds, of with I shot the last at an 200 yd IBS match yesterday
in 29 degree weather.....Across the board with the five powders, I
found that at lower loads from 2675 to 2750 fps, both primers were on
par with accuracy and Lab Radar numbers. As I approached 2775 and
into 2800 fps, the BR2's took over for accuracy, and in some cases
huge. Ramshot Hunter and the BR2's were the top of the list. By directly
replacing the primer going to the WLR, the groups fell apart. I did bring
the groups back together but adding more jump, but the WLR cup started
to show cratering. At that point, I switched back to the BR2. Lab showed
18 more FPS, and no cratering. The WLR cups were not handling the extra
pressure.....My findings for a given cartridge.

Powders tested......R-16, R17, Staball, Ramshot Hunter, H4831sc and R-23.

[darkker]

the BR2's took over for accuracy, and in some cases
huge...replacing the primer going to the WLR, the groups fell apart.

....but the WLR cup started to show cratering. At that point, I switched back to the BR2. Lab showed
18 more FPS, and no cratering. The WLR cups were not handling the extra
pressure.....

You have two different concepts you are speaking to here: Accuracy and perceived pressures.

I completely agree that accuracy can be impacted rather greatly at times, with primer changes.

As far as the cases or cartridge size families I've tested, the actual pressures haven't been impacted in a meaningful way.
The "signs" of pressure can show up rather differently, for a pile of reasons. The trap to not fall into, is to think they are reliable in telling you anything other than, a component is about to fail.

Here are a few examples.
When pressure testing some bullet pressure claims in the Creedmoor, does the left side or right side look higher pressure?

https://photos.app.goo.gl/EY8vfUiAeWgPrhcs9

Most would say the left side had higher pressures. Statistically, the pressures were identical.
https://photos.app.goo.gl/PC1SE71P6yNN4jhn9
https://photos.app.goo.gl/BgD1c792Pne5N29VA

Excusing the shot to shot trigger variances, here are some traces swapping Wolf and CCI
https://photos.app.goo.gl/L18WG3wgn52em2Q6A
https://photos.app.goo.gl/rTY9Y5qAUNcYWY9X9

Cheers