Going to inspect the 442 UC I ordered. As well as fit and finish I'm taking snap caps for trigger feel and feeler gauges for barrel cylinder and headspace. Don't know what I'm looking for on the last 2 because my Model 40 has .005 barrel/cylinder and .009 headspace and my 640-1 PC Pro Series has .009 barrel/cylinder and .016 headspace. Any advice? I know the newer guns have the frame mounted firing pin and the 640 is 357 mag but I don't know if that's why there is the difference. What should I be looking for on the 442?