I've always preferred the lighter bullets in 9mm.

147 grain loads were abysmal when they first appeared. They simply didn't expand.

That's obviously changed - and there are some good 147 grain loads out there. Even I have some.

For those that have both - do you switch from a lighter 'summer' bullet to something heavier in winter? If so, what are your choices?

Looking at ballistic testing online, I don't see any demonstrable penetration benefit for the heavier bullets - which is why I'm asking.

Heavier winter clothing isn't a big deal here, but in general, winter brings more layers of it.

Is it a concern in 9mm?

I'm 100+ miles north of the valley of the damned. I stick with 147gr standard pressure HST year around in 9mm. No 115gr or 124gr and no +p loads. I like Critical Duty 135gr but it's recommended for 4" pistols, whereas mine is 3".

People do dress in heavier clothing up here. Today it's 30 degrees and not getting much warmer!

147 gr. loads have come improved. I like the Winchester Ranger 147gr. SXT (Black Talon without the scary name). I feel fine carrying it year round.

That's what I have, Winchester Ranger 147 SXTs.

Have switched to them in the winter instead of 115/124 variants of Gold Dots, 9BP, 9BPLE, HST, Golden Sabers and SXTs.

But for some reason I caught myself - why am I doing this? Is there really any advantage? Anything to be gained?

I'd contemplated ordering more 147's, but is there any advantage to to them in general?

As long as they perform as advertised and open up reliably and staying in the body I suppose there is some gain in energy transfer due to the heavier slug. Honestly, all of the rounds you mention would probably do just as well. 9mm performance has come a long way in regards to effectiveness.

The heavier bullet hits harder, but lighter bullets have flatter trajectories. I like to shoot handguns at the 100-yard line, so the flatter trajectory matters to me. I find that 124-grain is a nice compromise between the two extremes.

If you only shoot at closer ranges, or concerned whether you could punch through windshield glass (e.g. law enforcement use), the argument for the heavier projectile may make more sense.

Thank you gentlemen for the replies.