I don't think it's the metal, Fran, but it may be the ratio of the gauge to the weight of the bracelet. I asked our WS Faculty chainmaille expert, Lena Bugrimenko, for her opinion too. She suggested increasing the jump ring gauge; for example, if you are currently using 20-gauge, try using 18-gauge. Lena also gave me a great tip by mentioning that she sometimes uses a smaller gauge jump ring, like 20- or 21-gauge, but uses two of them at a closure point!
I actually followed her advice just yesterday. I made a rather expensive gold-filled and Akoya pearl necklace and I was worried about using a 21-gauge ring to attach the trigger clasp (we all know that the chain could get caught in the jump ring and work it open). So I made two 21-gauge rings (full hard wire, as I always use with my occasional jump rings). Both jump rings fit easily into the trigger clasp. How cool! (Thanks Lena!)
Answer contributed by Dale "Cougar" Armstrong