Zeroing my rifle

[Kadonny]

I was at the range this week zeroing one of my ARs with my Primary Arms 2.5x scope (fairly new to me but I really like it) and got to really thinking about the reticle on it. Here is the sight picture.

I understand bullet drop, but I'm trying to reason it out with this reticle. So PA shows the center dot to be a 50-300 yd shot, with each bdc dot to be another hundred yards out maxing at 600 yds. For reference, that day I was shooting 100 yard targets and 200 and 300 yard metal plates (torso sized).

So I'm thinking for overall use for me, I should zero the center dot at 100 yards, then each corresponding dot below would be another 100 yards. That would allow my scope to guide me out to 400 yards (about the max I can see anyway with the 2.5x zoom with my older eyes). This will allow me an easy thought process when sighting longer shots, but still give me the flexility of shooting in closer (using the scope reticle as shown) should I ever need some CQB shots. Afterall, if I need a 50 yd shot, I would just use my second dot as a guide (50/200 zero). I ended up zeroing the center dot at 100yds. Am I on the right track here?

Second question. What distances do you all zero? I have my Sport with a standard red dot zero'd at 50 yds figuring I'd use it more for close quarters and shorter distances but wondering what others do.

Thanks.

 

[vmumford]

I Zero all my Rifles at 50. 223 and 556 have different drops so my best all around works at 100-200 yards and a little high at 100 with 556

 

[cyphertext]

Forgive me for being a simpleton, but what do the directions say to zero it at?

 

[ChattanoogaPhil]

I


So I'm thinking for overall use for me, I should zero the center dot at 100 yards, then each corresponding dot below would be another 100 yards. That would allow my scope to guide me out to 400 yards (about the max I can see anyway with the 2.5x zoom with my older eyes). This will allow me an easy thought process when sighting longer shots, but still give me the flexility of shooting in closer (using the scope reticle as shown) should I ever need some CQB shots. Afterall, if I need a 50 yd shot, I would just use my second dot as a guide (50/200 zero). I ended up zeroing the center dot at 100yds. Am I on the right track here?

The below charts are for a 55gr 3240fps at 50yd and 100yd zero. Notice there is not that much difference between 50/100yd zero. So if you zeroed at 100yd and attempted to use the bottom 600yd hash mark to shoot at 400yd you'd be shooting several feet high. I'm guessing that reticle is deigned for 223/556 50yd zero anyway.

 

[sgtsandman]

Without having the instructions in front of me, since the center dot is for 50-300 yards, I would zero at 100 yards. If they specify a specific round that the scope is designed for, I would use that round (bullet weight, shape, etc).

For example, my Nikon scope is specifically calibrated for 136 grain Boat Tail Hollow Point Match. I would use that to zero my scope and use a ballistic calculating app to compensate for other rounds. Nikon has an app called Spot On that is specific for their scopes. So, I can use that app to make dope charts for any other round the scope is not set for.

Correction: 50 yards. My brain thought one thing and my fingers typed another.

 

[Geo. T.]

Good Stuff!

This is a pretty good chart but there is one major problem and that is the 24 inch barrel. This spring I did a whole lot of shooting with mu M&P 15 OR with the 16 inch barrel. The load experience I had had was with a Colt with a 20 inch barrel and a Remington 700 in 223 with a 24 inch barrel.

I was right that the velocity would be lower but no as low as it turned out to be. 5.56 ammo with 55 grain bullets were well below 3000 FPS! Several were in the 2800 FPS range.

Where I'm going with this is that it is very unlikely that a BCD scope will be right on. They can be close but based on muzzle velocity and barrel length and bullet weight they will need to be shot to get the data with your combination.

One other thing a 2.5X scope will be little use at over 200 yards or maybe 300. In some scopes the dots cover 3 minutes of angel or more. That is covering up a lot of target at 600 yards!

 

[Grjfer]

According to primary arms, it should be zeroed at 100 yards.

 

[sgtsandman]

Geo T has a point. Barrel length will change the ballistics.

Here is an example article: 223 Remington/5.56 NATO, velocity versus barrel length: A man, his chop box and his friend’s rifle | Rifleshooter.com

This isn't the exact one I had in mind but it will do well enough.

 

[cyphertext]

According to primary arms, it should be zeroed at 100 yards.

And that would put you over 6" low at 300 yards... I just don't see how the BDC would be very accurate at all with this particular scope. It's almost like SKS accuracy... will score hits on a man sized target... might hit them in the head or the big toe, but hit. Unless I am just missing something with this one.

 

[Kadonny]

Thank you all. Phil, great chart, thank you very much that helps a ton. I see now that the two zeros are not hugely different at those distances.

I can't find my instructions and can't seem to find a set online. Grjfer, can I ask where you found the 100 info?

I guess I'm trying to shoehorn the BDC dots into 100 yard increments and that will not necessarily be correct. This is on top of my 20" bbl rifle, so I will get higher velocities than a carbine. I am shooting the Wolf Gold 55gr.

The problem is at my range a 300 yard shot is about the max I can shoot, and it's even hard at that range to see exactly where you are hitting (I guess I need stronger spotting scope) on paper. If I can nail down exactly the bullet drop on my rifle with my loads in relation to the dots, then that's the real ticket.....the problem is figuring that out with the longer shots.

I think Cypher is right, this scope is more of a battle scope and the BDS dots are a rough guide. In that case all that matters is a hit, whether it be head or toe and there is a lot of margin for error on a 6' tall target. Maybe I'm trying to be too precise here with this particular scope.

RE: the 2.5x, I have no problem seeing targets at 300 yards with it (torso sized steelies) that's why I'm sort of saying I think 400yds would probably be the max I can see with my eyes and this magnification.

 

[ChattanoogaPhil]

This is a pretty good chart but there is one major problem and that is the 24 inch barrel. This spring I did a whole lot of shooting with mu M&P 15 OR with the 16 inch barrel. The load experience I had had was with a Colt with a 20 inch barrel and a Remington 700 in 223 with a 24 inch barrel.

What I was illustrating was the difference between a 50 and 100yd zero.
3240fps or 2900fps same lesson. (2900 below)

The OP was thinking that he could go from a 50yd zero to a 100yd zero and that would somehow make each holdover dot an extra 100yds -- 200yd, 300yd, 400yd bottom dot. The charts were to illustrate how that's not going to work.

 

[Grjfer]

And that would put you over 6" low at 300 yards... I just don't see how the BDC would be very accurate at all with this particular scope. It's almost like SKS accuracy... will score hits on a man sized target... might hit them in the head or the big toe, but hit. Unless I am just missing something with this one.

Hey, I agree with you. I prefer a 50 yard zero. I'm just stating what PA recommends with said reticle.

 

[BAM-BAM]

Keep in mind that's a "combat" recital....not a precision target scope.......out to 200yds the POI is within 2.5"... cus at contact distance... the muzzle is 2.5 inches below the dot

50-200yds POI is within 1.3inches of POA

 

[ChattanoogaPhil]

Thank you all. Phil, great chart the really helps me.

I guess I'm trying to shoehorn the BDC dots into 100 yard increments and that will not necessarily be correct. This is on top of my 20" bbl rifle, so I will get higher velocities than a carbine.

The problem is at my range a 300 yard shot is about the max I can shoot, and it's even hard at that range to see exactly where you are hitting (I guess I need stronger spotting scope) on paper. If I can nail down exactly the bullet drop on my rifle with my loads in relation to the dots, then that's the real ticket.....the problem is figuring that out with the longer shots.

I think Cypher is right, this scope is more of a battle scope and the BDS dots are a rough guide. In that case all that matters is a hit, whether it be head or toe and there is a lot of margin for error on a 6' tall target. Maybe I'm trying to be too precise here.

I think you'll find the reticle too small and magnification too low to do any precision shooting at distance. And the velocity difference between a 20in and 16in barrel would be typically around 100fps.

I'll pluck numbers from the link earlier in the thread.
UMC 55gr .223
20in - 3071
16in - 2968


Take a look at these two charts and ask yourself if you or the reticle will know the difference of 100fps at the longest you can shoot which you said was 400yds. Bullet drop difference is 3 inches at 400yds. At 300yds a mere 1 inch.

 

[Kadonny]

I think you'll find the reticle too small and magnification too low to do any precision shooting at distance. And the velocity difference between a 20in and 16in barrel would be typically around 100fps.

I'll pluck numbers from the link earlier in the thread.
UMC 55gr .223
20in - 3071
16in - 2968

Take a look at these two charts and ask yourself if you or the reticle will know the difference of 100fps at the longest you can shoot which you said was 400yds. Bullet drop difference is 3 inches at 400yds.

Yeah, it's pretty clear now it won't, thanks. So end of the day I zero'd at 100 so I think I can rough guide out the dots to my 400 yards max and it won't significatly be different than what they show on the picture.

Again, thanks all.

So......if I am looking to get a more precise scope to shoot out to 400, what magnification should I be looking for? Forgive me, I'm new to the longer distance shooting. I joined a new rifle club and now have a 300 yd range and some 400 yd steel targets to shoot on the longest range. I'm really just starting to shoot these distances and trying to get the hang of it.

Here is my set up, just for fun.

 

[Biggfoot44]

The other factor to keep in mind is that the usual ballistic charts/ programsb are calculated on the basis of 1.5in sight line above bore center. This is reasonable for low mounted scoped bolt actions, but an an AR particularily with optic will be more like 3 inches.

The part that throws me about the reticule in question is the supposed 50-300yd zero for the initial dot. That would seem to be making use of the military Battle Zero whereby aiming at center torso would result in a hit anywhere on the body. For civilian/ sporting/ recreational, anything requiring precise hits at moderate think of the initial dot as more like 50yd to almost 200yd. Conversely doing some quick conversions into MOA holdovers, the longer dots are reasonably close.


To sumize for the OP;

Zero initial Dot @ 100yds, and treat it like a 100yd zero. Treat actual +/- 300yds distance as aprox half way inbetween the initial Dot and the 400yd Dot, and take 400-600yd dots at face value, subject to actual testing.

Yes, I am big fan of 2.5x scopes. Great field of view and fast target aquisition, capable of good acuraccy to much farther than commonly thought.


And yes, for sighting system with one aiming point, I favor 50yd zero.

On my shorty AR , I currently have conventional 2.5x scope, zeroed for 50yds.

 

[ChattanoogaPhil]

The other factor to keep in mind is that the usual ballistic charts/ programsb are calculated on the basis of 1.5in sight line above bore center. This is reasonable for low mounted scoped bolt actions, but an an AR particularily with optic will be more like 3 inches.

.

That's why I set each chart at 2.5in sight above bore which is about right for that scope and typical for an AR optic height.
Notice each starts out at zero yards 2.5in low.

 

[Goblin]

Let's talk about the standard sighting procedure for the carbine with iron sights. With the rear sight bottomed in the 6/3 position, you zero at 25 meters using the small aperture and front sight for elevation. This is the 300 meter zero because the standard load will cross the line of sight at 25 and 300 meters. It's never more than about 2.5" over line of sight between those distances. Then flip to the large aperatire marked 0-2 and you're zeroed at 200 meters.

My guess is that your sight s at such a height that the standard load will cross the line of sight at 50 and 300 yards instead of the 25 and 300 meters discussed above. I'd try a 50 yard zero then test at 300 yards to see how close you are. These ballistic reticles aren't magic, there will likely be a variance for your rifle and ammo, but this would be where I'd start.

 

[ChattanoogaPhil]

Yeah, it's pretty clear now it won't, thanks. So end of the day I zero'd at 100 so I think I can rough guide out the dots to my 400 yards max and it won't significatly be different than what they show on the picture.

Just for giggles I called Jeff at Primary Arms. Jeff says the reticle is designed for a 50yd zero. Makes sense since it's labeled a 50-300. Take another look at post#4 and compare 50/100yd zero. But like you say it's not that big of a difference, and for example if most all of your shooting with this optic is between 100-200yds then 100yd zero would be great.

 

[Kadonny]

Just for giggles I called Jeff at Primary Arms. Jeff says the reticle is designed for a 50yd zero. Makes sense since it's labeled a 50-300. Take another look at post#4 and compare 50/100yd zero.

Wow, thanks for calling PA directly. Very nice. I did look at the charts and as I said, they helped tremendously and I can see now there is not a huge differnce between the 50 and 100 zero. I can live with my 100 zero. So what's with the 50-300 label? Is that the whole "inner ring" I would assume? In that ring will be a hit at the 50-300 ranges.