SmallCaliberCentral

How big of an effect does useing differant primers have on pressure?

If we're talking the 204 at somewhat normal seating depths well off the lands and within book data the answer is not much at all.
If theres one powder I'd worry about switching primers on it would be BLC-2. It never gave me any real trouble but it did leave me with the notion it deserves respect at book max charges.

Of course one must be wary of primer cup thickness before switching.

Faster burn rate powders might show a greater effect than slow but thats really just a hunch on my part.

so would it be safe to use any small rifle primer in a 204?

Yes, provided you worked up the load with that particular primer. What can be dangerous is to just substitute a different primer in a maximum (or close to maximum) load that you've already tested though. If I want to change a primer on an existing load, I'll back it off a grain or so and retest, watching for pressure signs.

I will say that I've had better luck in the .204 with thicker cup primers like CCI Magnums or CCI BR-4. The standard ones I tried showed pressure signs even at starting loads.

jo191145 wrote:
Of course one must be wary of primer cup thickness before switching.

No. It is not safe to use any primer in the 204. Unlike LR primers SR primers come in varying thicknesses.
Remington makes a 6.5 primer (never seen one) This is reportedly the thinnest primer cup out there and
definately not for use in a high powered cartridge like the 204.

Personally by my first posts criteria I would not hesitate switching between the thicker cups with a particular book load in a standard factory chamber but thats just me.

One caveat. If anyone happens to have one of those bolts that craters primers with any load I'd worry a whole lot more.
Actually I'd have it bushed or sell it. I hate the whole idea.

does anyone know of a good primer that will work in both a 204 and a 22-250?

The 204 uses a small rifle primer.
The 22-250 uses a large rifle primer.

Beyond that I like Fed 205M's in SR and Fed 215 Magnums in LR.