I installed an ALG Defense ACT trigger in the wife's S&W M&P 15-22 based on some reviews here. I installed it with the purple spring that's rated at 4.5lbs.

Will this be sufficient for .22LR ammo? She really likes the feel of this trigger and would like to stay with it at this weight. If others have had issues I'll just switch to the 6lb Tan spring. Even the 6lb would still be smoother than the factory trigger.

I will be buying more of these for my other AR rifles!

Fired 100 or so CCI MiniMags and everyone fired with the 4.5lbs spring so I'll leave it unless I have issues.

I also have have an ALG ACT trigger in my 15-22, I purchased mine when only came with one hammer spring but later installed a JP reduced power hammer spring (red) and thousands and thousands of rounds later still works like a champ. I put through a lot of different brands of ammo but for the most part I use bulk packs.

Do standard AR triggers fit these 22lr’s?? I had no idea

Yes the 15-22 uses a standard AR trigger group.

Fired another 200 or so in 35* weather, no issues. While the temp shouldn’t affect the trigger directly, the ALG GoJuice worked great, no function issues.