I've used both the front trigger and the rear trigger first.

Both methods seemed to hit well enough in my double for regulation purposes.

My last PH in Zimbabwe said a lot of guys DO get double discharges when hunting from his actual experience. But my guess it never appears in their hunt stories.

A lot of guys also do CHOOSE to use the rear trigger first. The above is one reason.

What I would do is try both methods with your Blaser. If using the front trigger goes OK that would be the best choice.

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"I just bought a Blaser S2 in 500/416, and after firing 8 rounds, am not sure I want to tap off either trigger again."

Good to read you've bought a .500/.416. Would like to hear how you go with it over time.

The .500/.416 is reported to recoil almost as much as a .470 BTW.

Don't do too much or any shooting from a bench with your big bore. A standing rest is better to lessen the recoil effect on your shoulder. Also eight shots are more than enough to start to seriously hurt on any big bore if shooting paper targets. I personally try to shoot a maximum of 6 to 8 round off at a session. If shooting more, I then switch to a lighter recoilling rifle for a while before shooting more rounds from the big bore. Use some padding too.