I have a 10" DD 300BO pistol.  I just got an Aimpoint PRO for it and now need to zero.  I have a Surefire mount on it and a 300SPS on order so it will have a can.  In all honesty this wont be used much at all but Id like to have it setup.  I am struggling to find a good zero for both rounds.

I assume the effective range of a sub 220g round is under 100 yards for me and probably under 50 in a realistic scenario.  I can see the super going out to 200 or more but thats just a bonus.  So I think the best way to zero is by doing a 50 yard super zero at 150g bullets.  I think this will still get me within 2" up to 60 yards with a 220g round but a whopping 16" drop at 200 yards with a 150g.  

Then we have to throw in the 110g round ballistics.  Its a mess.  Anyone in the same spot w a red dot and 300?

Download ballistics program and plug in information to give you real good figures of what you are going to get from your bullets.
Remember a 50/200 type zero is really zeroed for 50 and not 200 until you actually shoot at the longer distance.
Shooting a group aimed at a 100 yards to check rise against your 50 yard zero is a little better than not checking at 200 but not much.

The 50/200 thing is worthless with 300blk.

My subs zeroed at 50yds and the supers shot 8" high.

Pick a load and sight in, and write down the numbers and start over with the other load, and write down the numbers.

Agreed.  There is so much difference you won't find a happy medium.

Here is a 110 V-Max load (towards the upper end of 300BLK velocity) compared to a 220 SMK load that is subsonic.    To get the initial ballistics to line up I show the V-max with a 50 yd zero and the 220 SMK with a 25 yd zero.   This would be about as close to representative a I could make.

I.e. if you did have a 50 yd zero on your supers, you would probably be pretty close to a 25yd zero on Subs.   But past that you have to pretty much hold way over for a reasonable chance of a hit with subs.

I zeroed supers at 50 and when I shot subs at 25 the poi was further off to the right then it was off vertically.  This was suppressed, dont think I checked unsupressed.

So now I only shoot subs.  Its more fun that way anyway.  I have considered a second optic for hunting with supers.

All this info helps.  Subs at 25 and Super at 50.  Subs are not good past 75 yards and supers past 150 with this zeoring.

Yep, that's probably a pretty good rule of thumb.   The software I used was "Point Blank" and is freeware you should be able to get off the web to play around with some other trajectories.   If you are really good at math you could solve the ballistic equations for the two curves to see where there are other good combinations.

Just for fun I played around a bit more, and basically made my range increments a bit finer at 5 yds.  What I'm looking for is the point at which total drop = 1.5", which is the height above bore of my optic.   As we all know, when we zero our optic our line of sight is considered the "baseline" and then the barrel actually is angled up relative to our line of sight so that the bullet trajectory intersects at our zero range.   For close range zeros on relatively slow projectiles we typically see that we just "kiss" that curve, and for longer range zeros on faster projectiles we usually have 2 points where it crosses the sight line...the first usually pretty close range and the other out at the longer ranges (so example are the 25yd / 300m or 50yd 200m zeros for an AR15 in 5.56).

Since the 300BLK is pretty slow there aren't many practical zeros that give you two points like that so I just assumed that we'll "kiss" the sight line at our zero point.  That would mean that as you push the bullet up to where it tries to reach that cross-over point you have to angle the barrel such that it makes up for that 1.5" of sight off-set figuring that the initial part of the trajectory curve is close to a straight line.   For a 1.5" sight offset and the loads that I have worked up, I get some of the following nodes:

50yd zero with 110Vmax = 30 yd "zero" for the 220gr subsonic.

If I apply a 4 MOA cone to that for a 4 MOA red dot such as the PRO, the 110V-max says in that +/- 2MOA cone out to about 125 yds and is just outside at 150.

The 220 falls outside somewhere around 60 yds.    So those could be practical point blank zeros if you ran a red dot in that you'd expect all shots to be within that dot inside of those ranges.


Now...you could go for a 25yd zero on the supers to get a bit better longer range performance.   That puts you about 1" high from 50 to 100yds with the 110, but then it doesn't drop out of the 4 MOA cone to more like 175yds.   The nice thing is that because the subs are so slow, you won't have a huge POI difference and would be fairly close at 25yds.    


With a 25yd zero, it also gives a nice trajectory for a 150gr FMJ that crosses back over close to 100yds, and some of the 125gr hunting bullets will be about that same point.    For that reason I've gone to a 25yd zero on my 300BLK and just assume its "close enough" on subs at closer ranges.

I follow what you are saying here.  I have 110 (not that many), 150g for target stuff, and a lot of 220 for sub.  So a zero where all would work would be nice.  Id like to zero with 150g bc those are the cheapest and I can waste rounds zeoring and target shooting.  And then know where the 110 and 220 will fall in the chart.  

Can you graph this?  5 yard increments and out to 200y max.  Id like to see it for myself with a 25y zero and what 110, 150, 220 look like.  And could I 25y zero w 150g and make this work still?  In a real life scenario I am never using 300bo past 150y and probably never past 50 yards.  Its going to be a special use weapon if its ever needed.  I am not going hunting with it.  So 220g subs are what would be used but it would be nice to be able to drop in 110 or 150 if thats all I had and know my POI isnt off by more than a few inches and I can make effective hits.

Now that I said the above...  I might need ANOTHER dbal a3 for the 300 bc it seems like the perfect nigh vision setup with a suppressor.

If you can send me the velocities you have with those loads, and the bullets you are using I can plug them in to tweak this a bit.  That will impact the longer range portion more than the initial 25yd zero   Note that I have to try to tweak the trajectory of the 220gr to match since the way the tool plots is based on the zero distance put in for a particular load.  So it doesn't necessarily say if you are zeroed at 25 with the 110, here is where another load will hit.   The good news is that at 25yds there isn't difference between any of the supersonic loads.  The 220 is funny because it is so much slower, and that if you have a shallow enough angle to get the zero on a supersonic load and sight above bore you can come to a place where you may actually never quite rise all the way up to the sight line.

In fact, to zero the 200 at 50 yards it will actually cross the sight line at about 20 yards and be on the way back down at 50.   To match up with the 25 yd zero of the others it is pretty close itself.



The data I'm referencing is as follows:

220 SMK at 1046 FPS.
110 V-max at 2100 FPS
125 Nosler BT at 1800FPS
150 Hornady FMJBT at 1700 FPS

This is what I go with:

10/100 yard zero for subs
25/150 yard zero for supers

Based on:

I recognize that plot!

It's worked with me. I have it saved on my phone as a quick reference just in case. Generally I zero for supers and when I shoot subs at the range you can shoot subs, I'm close enough to the reticle to hit steel.

Cool, glad it has worked for you!   I put that together a few years ago in response to some similar questions about trying to get a good zero to work for both supers and subs.   They are so different that its really tough to do both, but as mentioned earlier, 25yd does get you close but the subs drop off the face of the earth realy quick.  

Here is a slightly larger version from my photobucket acct.   Note that it would take an entirely different zero to achieve the trajectory shown for the subs.   I might play around with it though to see what the supers would do if zerod at 10yds....

So just for fun, I played around with what it might look like to zero a rifle for subs at 100yds.   That would give you roundly a cross over point at 9yds or so.   Results are interesting, but perhaps useful to the indirect fire fans!






110gr supers (2100FPS):

6" high at 50
11.5" high at 100
14" high at 150 (close to the peak)
back to zero at about 320 yds.


150gr supers (1700FPS)

5.5" high at 50
9" high at 100 (close to the peak)
back to zero at about 240yds.

Awesome (and thank you)! It's amazing who you meet on the Internet.

You are welcome!  And I'm just a normal guy like everyone else.  Pretty cool to see something I put together has made a few rounds though!

If I zero subs at 10/100 it will match up supers at 25/150?  Or so I have to do adjustments?  

You will have to make adjustments.  If you look at the picture Joker posted (and my larger original version) you can see that the initial trajectories are way different.   Remember that with an optic that is mounted above the bore, that when you sight it in, you are actually sighting such that the barrel is on an angle "up" towards your sight line.   This angle is set based on where you zero the rifle and doesn't change when you switch ammo.  So, if you zero your subs at 10/100 you'll get the trajectory with supers that I posted that has the big rainbow arcs...they will still be zero'd at about 10 yds, but will be launching like mortar shells down range.

From what I've seen so far, the closest to a universal zero is 25 yds, but that means that subs require a pretty big hold over past 50 yds.

I'm building a 300 blackout pistol with a 9" barrel & will be shooting supersonic ammo for the foreseeable future.

Range only goes from 25 to 100 yards & I'm trying to figure out what optic and bullet weight.

Been bouncing around between the Aimpoint Micro, a MRO or a 1x4 30mm scope......

What is a good starting point for a realistic zero.

I'm leaning more and more towards a 25yd zero for a good all around zero for range use, and as shown in the graphs, is pretty useful out to 150-200yds with some supers.