attaching brass shell casings

We're attaching three spent shell casings to a mat backing, and I'm thinking about how to do it. The customer's fine with hot glue, and we only use the non-corrosive electrician's kind, but I'm thinking a mechanical hold would be longer lasting and less interactive. (Too, the hot glue has a set

Amazing DIY Crafts by a Talented Woman

Three-piece fastening set - brass + brass

Incipient Case Head Separation?

Uberti 1876 in 45-60 ejector issue or brass ???

DIY Bullet Shell Casing Necklace

Brass Catcher Spare Mount, Durable Picatinny Mount

Instead Of Buying New Ammunition, These Gun Enthusiasts Recycle By

Crafty Uses for Brass Casings - Ammoup

PRICE REDUCED Bullet Money Clip / 45 Colt Money Clip / Colt 45

Why does my brass look like this ?

Recycle Brass Shell Casings: How To Dispose of Bullets (Like a Boss)

Complete Precision Case Prep within

When/who invented modern bullets (where the bullet is attached to the gunpowder casing)? - Quora

DIY Bullet Shell Casing Necklace