I'd be more tempted to check for coil binding first.
I've used piper and Kent for years, the kent do run in easier due to the phosphate coating they have, as it retains oil better, but after 20 mins should be fine, if it is allowed to idle for any length of time before this it can wipe the nose off the lobes.
That is why I always try to use regrind rather than new, as it is already work hardened metal.
tabetha