I have to agree with Lawnboi, the highest rated silicone plugs are rated around 27-28 NRR, that actually is about the same for most custom molded ones too since they mostly use a similar material, while most of the better quality foam plugs get you 33 NRR. If you then add 20-30 NRR rated earmuffs over that you don't end up with 53 NRR, instead your actually around 35-38 NRR, with the 28 NRR silicone plugs you'll be right around 30-33 NRR, or about what you would get with foam alone.
That means that your gunshot, which we'll say is around 150 dB, you're still going to "hear" it at 120 ish dB assuming you are using your plugs and muffs properly. But because of the dB is measured that actually translates to the gunshot being "heard" at about 1/4 of the volume that it would be unprotected.
So for the most effective hearing protection, I would recommend try several different brands or styles of foam earplugs to see which one fits your ear better before you resort to silicone ones.