Zero Distance for 25-50 yard shooting

[KenP11A]

Hello all, I'm currently training for a NRA PPC course of fire (Match 5 & 12) to test to become a Firearms Instructor at my LE agency.

 

For the unaware, this test is essentially 12 shots at 7 yards, 24 shots at 25 yards, and 24 shots at 50 yards, from various positions. My question is - what would be a good zero distance, assuming the majority of the shooting is from 25 and 50 yards? I was doing some ballistics math and figured if I zero around 40 yards my drop would be +0.4 at 25 and -0.7 at 50 yards. Unless it would be better just to zero at 25 and remember my drop will be ~1.5 at 50?

 

Using a Glock 17 with Dawson Precision adjustable iron sights. 

 

Bonus question - What would be the best shooting position to zero from? Just bench rest? Or standing unsupported? I can shoot perfect grounds at 10 yards but backing up to 40 I'll admit they start to spread out. The test involves shooting standing unsupported, kneeling, left hand from barricade, right hand from barricade, sitting, and prone. 

[Guy Neill]

Without running any numbers, the 40 yard zero does not sound bad.

 

Zero from a bench to eliminate as many variables as you can.  Then, verify offhand.

 

 

[gargoil66]

Ken:

 

I would go with a fifty but that's because I will only have to use a hold at 7 and 25.  A forty zero?  It is low for fifty and my bet is that given how the eyes and body work under the stress of timed fire, that you will end up having to use a high favor at fifty which means now you have to use three holds for the course.  So, I would go with fifty myself and if it shot high in that oblong X ring, I would be pretty happy.  Just me.  

 

The big thing is for you to test your ideas before committing to them.   I doubt you will get away with a center of mass hold for the entire course so test your plan first.  

 

Here is what I would do.

 

I would get a zero at fifty on the target from a supported position where my eyes are in as natural a position as possible.  Head relaxed and eyes not under strain.  Then confirm from a unsupported position.  It will probably be different so adjust zero based on calls but don't spend a lot of time with it.  You will have the opportunity to adjust again.

 

Put up a new target, go to seven yards and hold center for five.  See where the group went with a center hold.  I would expect it to be pretty low.  Maybe 9 ring on the B-27?  Would look at the windage and if it is too much to one side or the other for my liking, I would make an adjustment.  

 

Go back to 25, hold center and see where the group went.  Am sure it will be low but you need to figure out if you can deal with it when shooting at 25.   Look to see if the windage is good.  If not, adjust windage as you see fit.

 

Go back to fifty yards and shoot again.  See if your zero held and if your windage is now OK.   Elevation may be off some but the windage ought to be decent.  Remember that those silhouettes have vertical oblong scoring rings.  Higher than wide.  You can make more mistakes with elevation than windage.  

 

New target, shoot five at your distances using holds and see if your eyes like the holds.  In other words, did you score well and were you confident in what you were seeing? 

 

If so, you have a decent zero.  If you do not like what you have to see to score well with your holds, give a try to a 25 zero but I think you ought to be OK with your forty or a fifty yard zero. 

 

GG66

Edited December 19, 2021 by gargoil66

[Guy Neill]

I don't know all the details of the ammunition you are using, but with a 115gr FMJ with a BC of 0.140 and velocity of 1135, the numbers for 50 yards look to be.

Trajectory

Zero        40         50

Yards     PoI         PoI

0            -0.5       -0.5

10          0.1          0.2

20         0.3         0.6

25         0.4         0.7

30         0.3         0.7

40         0.0         0.5

50         -0.6        0.0

 

So take your pick.  Both should allow essentially holding center at each range.

[gargoil66]

2 minutes ago, Guy Neill said:

I don't know all the details of the ammunition you are using, but with a 115gr FMJ with a BC of 0.140 and velocity of 1135, the numbers for 50 yards look to be.

Trajectory

Zero        40         50

Yards     PoI         PoI

0            -0.5       -0.5

10          0.1          0.2

20         0.3         0.6

25         0.4         0.7

30         0.3         0.7

40         0.0         0.5

50         -0.6        0.0

 

So take your pick.  Both should allow essentially holding center at each range.

Guy: 

 

Roger, I understand what ballistics programs produce but they represent what happens under very strict and sterile conditions.  Basically sight height, time of flight, and gravity.  Reality is almost always radically different than the data produced by ballistics programs.  Not because gravity changed, but because velocity isn't the same, sight heights aren't the same, grip and stance, and particularly how guys see sight pictures at different distances are not the same.  

 

Some experiences guys take with them for their shooting careers.  One of the bigger ones for me was actually testing danger space estimates based on computer programs, on paper, at real distances.  Was so dramatic that it influences my thinking on zeros for danger space use to this day.  

 

40 or 50 yards?  I would go with fifty and here is why.  Why would I want to deliberately put on a low zero for the longest and most challenging distance I have to shoot, where holding center is probably the most consistent hold I can have?  Particularly if about forty percent of the course of fire is done at that long distance.  It is way easier and precise for me to use a hold off at closer than farther distances.  

 

Bottom line though is what Ken finds gives him the most confidence that he has a good zero, knows his holds if he needs any, and that his training prepared him for his competition.   

 

GG

 

  

 

 

[Joe4d]

My suggestion is to getoff the internet and go shoot. COuld talk theory till the cows come home.
Id bench it at 25, then verify off hand, then practice on the 50 with a smaller target than your test.

[KenP11A]

Awesome advice, thank you all!!

[Zane1973]

I shoot PPC in SA. Only just started a year ago. I would suggest zero at 50. That would be X at 50. My point of aim varies in the positions at this distance. Base off X -standing with barricade. Top of X /top of 10 in seated and prone. At 25, POA is base of X, and at 7 it's base of 10. Hope this helps

[Steve RA]

Dead on at 37.5 yards.

[motosapiens]

i can't hold a 1.5" group at 50 yards, so I don't stress about this stuff at all. I zero iron sights at 18-20 yards and know that i don't ever have to hold over/under at any reasonable distance. beyond 50 i'll hold in the top half of the target and pray to whichever deity seems responsive.

Edited December 24, 2021 by motosapiens

[Kwontanamo]

I usually group 1” at 30yards or try to

[GOF]

Just me, but   "How big is the 10-ring, and how much space do you have to work with? X's are nice, but they only break ties, and most duty guns aren't capable of X-ring accuracy at 50 yards. 10s and 9s determine your qualification score. If you zero at 50 yards, where are you at 7 and 25 with the same hold? Do you have the space? If the space is there, why not just zero at 50 and concentrate on your sight picture. Ballistic charts will drive you nuts, but a solid hold, smooth trigger press, and a consistent load will alleviate a lot of problems. Just a thought.

Edited December 25, 2021 by GOF
spelling

[KenP11A]

Does anyone have any recommendations for ammo? Was dialing in my new sights and my groups varied between 1 and 3 inches at 10 yards. Using Fiocchi and Ammo Incorporated. I think I can actually say this is one the rare times it was the ammo, I was shooting bench rested + using my MantisX sensor/app (which said I was shooting 97+). With my old sights on the same gun, I used to be able to easily stack rounds on top of each other off-hand at 10 yards, but that was with a good batch of Winn 115 grain FMJ (which I have ordered more of). In the meantime, also have some Fort Scott and Geco I could try. Not into reloading so the ammo would need to be the mass-producted type

 

Also - is there a Brian Enos MantisX group that anyone knows of? Not sure how many other people use it, I love dry firing with it

[OpenshooterMclass4lyfe]

I would zero it at the distance that will give you the least amount of offsets