I have found my favorite .357 SIG target shooting ammo, Speer Lawman 125 gr. I have tried so many others and have settled with the Speer. It's a clean shooting round, a lot of pep, and more accurate than any of the other ammo I was shooting.
Myself and 2 other gun shooting buddies went in together and bought 1K rounds from SGAmmo.com for $299.80+$16.00 shipping.
What's your favorite .357 SIG target shooting ammo?

I agree, it's excellent ammunition. However, I have found a a decent alternative. A few weeks ago, Cabelas had SIG Sauer .357 SIG on sale for $18.74 per box. With a $20 coupon, its price for several boxes was comparable to SG Ammo's Lawman price. In my last two range visits combined, I've shot 100 rounds of each brand through my SIG P320 Compact. There was no discernible difference in accuracy at either 15 or 20 yards, and all rounds functioned perfectly. So if you can't find Lawman, SIG Sauer will do just fine.

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What, me worry?

I have had good luck with Defender Ammo and Freedom Munitions. One of my favorites is Precision One ammunition. I also like Wisconsin Cartridge company and Parabellum Research. Another great one is Master-Ammo company and really...the last batch of Ultramax ammo I got was outstanding!

My (limited testing) review Freedom Munitions:
Memorial day weekend (P229) fireworks..two Ooohs and an Ahhh! | The Leading Glock Forum and Community - GlockTalk.com

Ultramax test:

Glock 31 perfection! | The Leading Glock Forum and Community - GlockTalk.com