I replaced the factory plastic 16lb factory with a 18lb tungsten guide rod spring assembly from GlockStore.com. My input, Factory 16 is OK for all weather, In very cold weather you might want to drop to 14lbs. The reason I went to18lb tungsten is that the heavy tungsten (almost twice the weight of the SS guide rod) helps keep the frame more stationary and reducing rise while the slide is in motion, thus helping for next shot target acquisition. the heavier spring does little for felt recoil if any but it does reduce the rearward "smack" of the slide, thus, reducing wear and tear on the rearward slide limiting components and the front rail (unless you are shooting 10's of thousands of rounds through your G27 this probably will never be an issue). Keep in mind cold ammo burns slower and often causes ejection malfunctions, stove piping, carbon build up then the same feed issues similar to the effects of limp-wristing so never use anything more than an 18lb in a G27. If not for the heavier Tungsten Steel guide rod to help stabilize the frame -channeling more power to rearward slide movement, I would be useing factory 16lb spring. To each their own but this is my opinion and my reasoning. I own a G30, G30-s G36 G38 G22 G27 and a G38, I've put all the buttons and bell on all my Glocks for many years. So, I don't know if you specifically asked anyone in particular but I just thought I'd raise my hand here to give yo a long winded answer your question, Respectfully, .....CaptainCrooch