At what Distance Should I Zero the 300 BLK ?

My 300 BLK project has advanced a little further- I am now the proud owner of the legendary Troy Battle Sight system. I am impressed with the fit and feel of the sights but can’t opine any sort of review until I sight these babies in. That got me thinking about what range to zero at. The combat effective range – that is

The distance from a weapon system at which a 50 percent probability of target hit is expected, or the tracer burnout range.” [copied from FM 101-5-1 Operational Terms and Graphics]

of the AAC 300 Blackout is about 440m for a 9″ barrel when using supersonic ammo. So 100m seems like a wise zero point, right? Well, the 5.56 round in an M4 is combat effective to 500m but it’s standard to sight those rifles in at 50/200Yds. [ There is a difference between yds and meters but its negligible in terms of energy and point of impact (a couple inches). here the terms will be used interchangeably for that reason.

Why not zero the 300BLK the same way? Well there is a slight difference in trajectory between the two. 

5.56 has a trajectory like the one shown above – since we are talking carbines here pay attention to the bottom. Due to the curvature of the bullet’s flight path the point of aim is the same at 50yds as it is at 200yds. For other distances one must adjust the point of aim accordingly. However any deer hunter will tell you that shots past 200yds are uncommon as lines of sight further than this are also uncommon in much of the US. For that reason this seems like a pretty sensible approach (especially if you don’t like aiming 14-20in above your target for those long shots– which is what larger caliber rifles are for).

300 Blackout Trajectories


You can see here that the load has a big affect on the BLK- the 220gr subs drop like rocks at 125yds. That’s what I plan to shoot most of the time from this gun so it makes sense for my intended use to look at a 25yd zero leaving other supersonic loads only 2″ lower at 25yds and from there it’s memorizing the optic settings (set either super or sub to zero and memorize the other settings for yardage and point of impact), using a BLK reticle or mils. One of the nice benefits of the BLK is that you can switch mags from subsonic to supersonic and gain a substantial amount of range (75-100yds) and still perform at least as well as a 5.56 and in some cases better. 

There you have it- the verdict is 25yd zero for subsonic ammo, 75 yd zero if you will mix it up between both and probably 100yd if supersonic is your primary ammo. 

1 thought on “At what Distance Should I Zero the 300 BLK ?

  1. Pingback: Update: my new approach to 300 BLK Zero | kR-15: info and resources for firearms enthusiasts

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