Why is there a delay between the first 5 animals (shots), and the second 5 animals? Why not just give the total of 5 minutes for the 10 animals, in a 40 animal match?

I do not know if I am correct but here are possible reasons.
1. Some of us are old and weak. We need that break every five shots to put the rifle down and recuperate.
2. When you do not have a spotter, the 30 seconds allows you to score a bank. Scoring 10 or 15 in the fog of a busy firing line will increase the margin of error in scoring your card correctly. When I say "fog" I mean many different things that can cause confusion: strong winds blowing equipment and dust everywhere, rain blowing on you and your rifle, somebody protesting you over and over again for no reason just to rattle you, etc. You will forget to score when you think the wind is going to blow your rifle onto the concrete.
3. 5 continuous minutes has more potential for a person having alibis to get as many as 9 shots behind and have to shoot 9 shot alibis instead of a maximum of 4 thus slowing the whole match down.
4. We know that 10 meter Air Rifle Finalists stand motionless for 30 minutes. There are many silhouette shooters that are not in good enough health to stand the 5 minutes motionless.
5. Most rifles are holding 5 rounds. The 30 second break prevents Silhouette from becoming a magazine changing event and puts the emphasis on precision.
6. Some people who have single shot rifles sometimes have 5 shot loading blocks. The 30 second break allows them time to reload their loading block.
7. Personally I like that 30 seconds to talk to my spotter off the clock about what I might need to change for the next bank.
8. This last reason is a touchy subject and it has been many, many years since I have observed it but there are people out there who will shoot more than the 5 shots at 5 animals if nobody is paying attention. It is more difficult for officials to catch that in a string of 10 for a 40 shot match and a string of 15 for a 60 shot match. I think those people have quit Silhouette.
9. It is tradition. Silhouette records go way back. You do not want to change match procedures that might affect scores because it will cause two different eras when national records are set. When somebody sets a record they do not want an asterisk and a note beside it.
10. The 30 seconds allows a period of normal breathing. During the fire period most people are controlling their breathing.
11. The 30 seconds allows for a short mental break after a time of intense concentration on making sure you are on the correct target, position, breathing, trigger control, and place to break the shot while being attentive to the suggestions of the spotter.
Hopefully someone will reply with better reasons than these. That was a good question to think about.

It would work just fine for SB but HP might be a bit of a challenge.

Some ranges only have 5 animals each and they need to be reset between strings.

Then you wouldn't have 30 seconds or so to ponder the next five shots after hitting the first 5 turkeys! The 30 seconds is nothing and I usually have about a minute left on time so its a 90 second break for me. After a long marathon match gets to the end you are tired enough with 5 shot banks. Its the 30 minute+ relay breaks that hurt the most!

Dee

The sport began with high-power rifles--mainly sporting rifles. The break between the five shots gave high-power shooters some minor recovery time and more importantly, time to replace ammunition (a rule) on the benches, pick up any ejected brass and allow for some "minor" barrel cooling. And of course the original (Non-race gun type unlimited rifles) held five-rounds in the magazines and this also gave time to reload the magazine.