I have an M&P 15R that I am putting a 300 Blackout upper on.  I'm wondering if I should change out the orange hammer spring while I use the lower with my 300 upper?  Any concern about striking 300 blackout primers with a setup designed for the hard Russian primers?  Is it an issue or not?

ETA - This is not about S&W specific guns, it's simply about using a stronger hammer spring where it's not needed.  Will striking primers too hard (maybe piercing them) create a problem?  I just don't know the answer and thought I'd ask the question.

Dang, nothing?

You should have no problems. As far as I know the hammer spring can't increases the chances of piercing a primer. Firing pin depth and over pressure are the two most frequent causes I am aware of.

Lighter springs will frequently cause a light strike which on military/hard primers can be a issue.

Will be good to go. No change needed.

Muchos Garcias.

I'm putting the 15R upper and the 5.45 ammo away in favor of .300 Blackout / Whisper assuming the market for that ammo returns to normal or get's normal!