You want to look at the trichomes not the pistols. Get yourself a jewelers loop to look.
Loop:
https://smile.amazon.com/gp/product/B00K0BGNNC/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1
Welcome aboard - plant looks good!
A Jewelers loupe is essential cheap and takes all the guesswork out.Your plants look great, and every grow is different. 2 plants of the same strain can finish a couple weeks apart,and breeders times are based on optimal conditions. They’re at best rough estimates.Good luck!
Like @Weedlover1 said. My last 2 harvest took 12 1/2 and 13 weeks.
My Durban Poison is at 12 weeks, and much of that is in 13 hours dark.
My Durbin Poison is at about 10 weeks but only 16 days on flowering light schedule. 
Welcome to the community. You will find many very experienced growers that are eager to assist when needed.
12 weeks of flower
Show us some whole plant pictures and close ups of your trichomes.
If you are 12 weeks on flowering schedule, you should be getting close.
@kaptain3d @Growdoc @Crazy81
Thanks Merlin, at 12 weeks, it’s likely time to start scoping trichones. Pistols don’t reflect readiness for harvest, they turn brown and recede before trichs turn. Look for all cloudy with a few amber ones for peak strength or more amber to get a more Indica effect. 
Keep in mind that flower times are APPROXIMATE, not cut in stone , plus we don’t count first two weeks after flip for transition period. Start counting once you see hedgehogs on budsights.
