If you have time to put on the electronic muffs, ok. If not you have to weigh the risk. The consequences of not using them is a risk of hearing loss. The risk of taking too much time to hunt them up is much higher. I imagine unless you wear glasses you won't be using eye protection either. Range rules get less important when fighting for your life.

Auditory exclusion is a reality. I had occasion to fire a .223 outdoors while someone else was firing a 7.62X54R and I heard 2 of his 5 and none of my 3 shots. (It's not a temporary deafness, I did hear my rifle cycle, but not fire.) No tinnitus, no hearing loss. Your results may vary.

On the other hand, I made the mistake of letting off a .357 once on the outdoor range with loose earplugs and my ears rang for over a day. The stress responce seems to cause that difference in outcome.

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Romans 13:3 & 4