These 3M/Peltor muffs that came out in past year or two have the best protection of any muffs I've ever used. Quantum leap over the stuff available even 5 years ago:
A) 3M Peltor X4: 27DB and very low profile. These are avail on Amazon, these are basically as low-profile as the old Peltor shotgunner muffs but block 27DB, almost 10DB more than the old low profile shotgunners.
B) 3M Peltor X3: 28 DB and moderately low profile. Maybe medium profile. It's only a 1DB difference between these and the X4's on paper, but in reality they seem much quieter.
C) Change up your eye protection to wire framed shooting glasses. Big thick plastic temples allow a huge amount of sound to leak into your muffs.
I've heard from doctors that plugs do nothing to attenuate the blast coming through the bones behind your ear, and that muffs are better. Best is using both.
My audiologist told me there is zero difference between the custom $150 molded plugs she made for me and Howard Leight max (33 DB) plugs. Aside from comfort.
My ears are hammered and I pay attention to this stuff a lot. I had two custom 35 cal suppressors made for me so I can run them on Whelens, 338 mags, and 9.3x62's. Trying to avoid unsuppressed rifle fire even when hunting. All the old time shooters and hunters I know are totally deaf.