AusVarmint

Out of my normal Rem7 1/2 primers that I use in 204R
LGS has heaps of Fiocchi standard small rifle Primers and magnum small rifle primers.
Thinking the magnum will do the job. What do you think ????!?

No experience with Fiocci primers mate, but I would think that a few "test" loads should do the trick.

I am sure I am not saying anything you dont already know.
As with any change of components a re-evaluation of the load and a load test should be conducted.

Yeah, I don't think that the Rem 7 1/2 are classed as magnum primers, rather have thicker cups, reduce your load, blah blah blah, et cetera and so on.

The cup thickness is the issue with 204 ruger primers

No experience with fiochi


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Looks like the SR Magnums would be the go for .204R, according to Fiocchi Italy;
https://www.fiocchi.com/en/category/pro ... line-taxon

Higher piercing resistance would mean thicker cup, I'd say.

Looks like their .204R factory ammo is USA loaded;
https://fiocchiusa.com/shop/ammo/rifle/ ... r-cat.html

A test of primers with a troubling batch of 2207 done a few weeks back may give you some insight into what you're looking for. One full grain over max ADI listing in a 222.
Nil issues with any of the primers shown but the S&B SR Magnum version cut groups in half at a later session. A lot of Fclass shooters are using them now with brilliant results at 900 meters in 6.5 Creedmoor and others. Speed and pressure is down from 3550 to just over 3500 which is consistent with magnum primers due to a far more consistent burn and possibly an expanded chamber volume from the primer launching the pill initially. I am testing 23 grains with them shortly to regain the velocity.

I know i have said this before on here but new batches of 2207 are a full 100 fps slower in both my 222s compared to batches back 20 years or more and have never shown the accuracy potential. The days of 20.5 grains of 2207 and a 52 Kats and off to a club comp are well and truly gone.