Apart from lobbing grenades at them? Anyone?

It's hindering my stealth tactics!!

Terminals or shoot them with silenced weapon.

I did a tactic from FPSs. Use cover, wait for the sentry to stop shooting, and pelt it with an accurate weapon (still a lowbie, so a 10mm pistol worked in my case.)

If you're lucky, you can find some cover where the gun can't shoot you, but you can shoot it.

Bigboy works very well against them

i've been using a sniper rifle from far enough away that even if the sentry shoots at me, its not likely to hit me more than once or twice.

Sneak, and use laser or energy weapons. I'm fairly low level (Level 8) and a non-modded laser pistol from Sneak will destroy most sentry turrets with 1 or 2 shots.

i find them easy to destroy with my modded 10mm pistol.

the one i got at the start of the game!

its only modded with a hardened mod.

take about 3 hits to destroy a turrent. mk1.

hard difficulty.

Energy weapons and they go down easy.

Scoped Energy Rifles. Don't forget to prone and hold breath.