Yes, I have those. They work quite well.
No, 23NRR is not enough. No number you'll see is "enough".
They take a noise that's, for example, 160Db, and reduce it AT MOST by about 33Db, making it 127Db, a number NIOS says your ears should be exposed to for no more than 1 second (I believe over a 24 hour period). If your gun is "only" 150Db and they reduce it by 23Db, you're still at 127. Plus, and this is someting most folks seem to miss, that number is an AVERAGE over a spectrum, usually like 25-20,000Hz or something like that. Some levels are much more than 23 but some ARE A LOT LESS.
If you're at a range, always use plugs and electronic muffs together. Hunting, single shots or just a few through the day, muffs alone will suffice. Never fire (or be near while it's being fired) any gun of any kind without hearing protection unless your LIFE depends on it.
