I think you're doing the right thing for the air weight with the coppers. To recall a snubby story. I knew a NYC Detective that got a call on a robbery in progress just down the street from where he was. Back in those days, the issue gun was a Colt Detective snubby with a 158g LRN cartridge. Dick told me that as he entered the store and ordered the crook to freeze, he spun around at the check out counter (gun in hand) and Dick put all 6 rounds into center of mass. The LRN bullets did little aside from scare the hell out of the crook and he was released not long after Dick saw him in court. I think you have nothing to lose but gain in an all copper higher vel loading. I carry Underwoods in my 380's and at some point will load lehighs in the 40 & 45 as well. Keep an eye on the primers. I wouldnt go past a very slight flattening over unfired condition.