Sights?

Clobbersauras

Clobbersauras

CGN Ultra frequent flyer
Rating - 100%
96   0   0
Location
Waaay out west.
Hi all - a few quick questions.

My Norc Typye97 Shorty has a 12.5 Inch barrel (.223). I was wondering what the AR owners who run 12.5 inch barrels have their sights set for? Right now I have mine zero'd at 25 yards which puts it high at 75 and about on at 125 - although I never benched it at 125 - just offhand plinked at the gongs (I know weird range set up, but our geographical features means we have to use 75, 125 and 200yds for targets).

What should I expect from this set up - i.e where should it be shooting at 100and 200 if I have a 25 yard zero? Is 25 yards the best to zero it at? It's a CQB gun so I figure it's about right, but being an armchair commando like I am, I could be wrong:D

Also do you have your optics zero'd for the same range as your irons?

Thanks in advance for the info.
 
I have a 11.5" and I zero it at 50. Optics (red dot) & Irons. If I had magnified optics I'd zero them at 100 and keep the irons zeroed at 50.
 
50 yard "improved battle sight zero" (IBSZ) will keep your shots within 2.6 inches(either high or low) from zero yards out to around 270 yards. The 50 yard cross over point is 250. At 25 yards I come out with around 1 inch low and at 100 yards my program shows 1.3 inches low. At 275 yards you are 3.1 inches low. The IBSZ allows for a "point and pull" zero for ranges up to 275 without corrections and still achieve hits.

TDC
 
TDC said:
50 yard "improved battle sight zero" (IBSZ) will keep your shots within 2.6 inches(either high or low) from zero yards out to around 270 yards. The 50 yard cross over point is 250. At 25 yards I come out with around 1 inch low and at 100 yards my program shows 1.3 inches low. At 275 yards you are 3.1 inches low. The IBSZ allows for a "point and pull" zero for ranges up to 275 without corrections and still achieve hits.

TDC
Click to expand...

Thanks TDC - this is the info I was looking for. Is that data consistent with a 12.5 inch barrel or is it for another barrel length?

This is a little disconcerting because when I range tested my rifle I was right on at 25 but I was about 6 inches high at 75 yards....how could that be? Come to think of it ,I did switch from .223 to 5.56 mid way through the test but still...6 inches is not consistent with your data....

I assume (due to the limitations at my range facility) if I sight my irons and optics to be 1 inch low at 25 this should bring me to an IBSZ set up?
 
The data provided is using a 55gr FMJ round with a BC of 0.237(pretty average BC) and a muzzle velocity of 3250. If you can shoot me some more accurate BC's and/or velocities I can fine tune the numbers.

The 25/300 military zero is crap. The goal was to produce 300 metre accurate rifles for competitive reasons. The mid range or 2/3 range trajectories with a 25/300 zero are around 8 inches high(above your sight line) at around 200 yards. That's a pretty big difference. This also assumes your optic is 2.25 inches above boreline which for an AR is about right, I could be wrong on that.

TDC
 
TDC said:
50 yards?? is that it! Come on, you aren't saying you don't shoot beyond 50 yards do you?

TDC
Click to expand...
I have mine set up as a CQB rig with an 11.5" barrel...50 yards zero will do.
I can still hit with ease out to 100 on irons,i have no use for further ranging with this set-up.
A 20" barrel and it would be a different story..
 
Hmmm....now I'm even more confused. I like Ronin's reasoning and I like TDC's data. I wonder if I went with TDC's set up where would it be shooting at 10-15 yards? I'll have to check this out next time I'm at the range. I'm still confused as to why I was shooting so high at 75 if I was right on at 25....I'm just not getting it I guess:confused:.
 
Its hard to say why you were shooting so high. A major issue with short range zero's is that "minor" differences in point of impact often turn into major problems at extended ranges. If you run a 50 yard zero you'll be fine for action shooting events as well as other uses. Again, if you have can get some more accuarate BC's for the rounds you shoot and velocities I can plug them into the program and give you some more accurate data to work with.

ETA: As a side note, I run my rifles with the 50 yard IBSZ for both my Irons and my Eotech. Hits at 200 on a pie plate are not a problem. I'm with Ronin, my rifle isn't setup for distance work, they're setup for relatively short distances(under 200 primarily) and rapid shooting.

TDC
 
Last edited:
Primarily I run american eagle but I don't have a Chrony so I'm out of luck there.

What barrel length do you use on your rig? The etotech if I'm not mistaken has a 1 MOA dot in the center of the circle right? I have an Aimpoint Micro on it's way which has a 4 MOA dot. A pie plate at 200 may be a little bit harder for my set up...
 
TDC said:
I agree, the 50 yard zero is ideal for close to all purposes. Does your 11.5 run without issues?

TDC
Click to expand...
Haven't tried this one yet,just bore sighted the upper.
But my last 11.5" ran perfect like that
I don't have a lower right now,traded it for an 870
 
Last edited:
In general, zero it 50 yards will pretty much give you a zero at 200m for most 5.56/223. in the field, error in range estimation will probably give you more grief than that few inches off here and there.
 
Last edited:
Clobb,

The best data I can find for 55gr FMJ is out of an 11.5" inch gun. The specs I found indicate a MV of 2670. I believe the average loss of velocity is around 60 fps/inch so lets play with 2720 out of your 12.5" rifle.

With that in mind and using the 0.269 BC (obtained from Federal themselves) for the dirty bird ammo. I come up with these numbers.

0.9 inches high at 100
0.3 inches high at 150
2.0 inches low at 200
6.2 inches low at 250
12.8 inches low at 300

This zero's crossover points are 50/160 with a maximum ordinate (max distance your bullet will be above your line of sight, from your rifle to second crossover point which in this case is 160 yards) of 0.9 inches high. This would occur from 100-120 yards distant.

If you zeroed at 30 yards, you'd have a crossover at 250. Your maximum ordinate would be 4.1 inches high and that would occur at 140 yards distant.

A 40 yard zero would produce a second crossover at just under 200 yards. Max ordinate would be 1.9 inches high. This would occur between 100-120 yards distant.

The above assumes the BC, velocity, and sea level pressures. If at all possible I'd stick with the 50 yard zero or the 40. The 30 yard zero would get you out to distance but it would cost you for targets between your crossover points. The 50 zero is very flat for the first 175 yards. I consider the effective range to be the distance where my projectile has fallen no more than my max ordinate. For example, the 50 yard zero had a max ord. of 0.9 inches. If we follow the ballistics until the projectile is 0.9 inches BELOW our line of sight, we have an effective "point and pull" range of 180 yards with a very flat trajectory. At the end of the day, with a 50 yard zero, you can rest assured that your bullet will not be any higher or lower than 1 inch out to 180 yards.

If larger targets are the norm, like shooting people in a war. I would extend my "point and pull distance" until my projectile dropped no more than 3 inches below line of sight. In this instance, that would yield a "point and pull" range of 215 yards(if you used the 50 yard zero). The 40 yard zero would extend that to 240 yards, and the 30 yard zero would extend that to 280 yards. With a 12.5 inch barrel. The energy at 215 yards is around 520 ft/lbs. At 280 yards you're playing with 430 ft/lbs.

If you want to play the terminal ballistics game, 55gr M193 ball will only fragment reliably to velocities at or above 2700 fps, and will tumble at velocities at or above 2500 fps. With your 12.5" barrel and the above specs. The max terminal effective range with M193(55gr FMJ) is 70 yards.. Below 2500 fps the projectile will not reliably tumble and will not fragment. It will still punch paper..

TDC
 
TDC said:
The data provided is using a 55gr FMJ round with a BC of 0.237(pretty average BC) and a muzzle velocity of 3250. If you can shoot me some more accurate BC's and/or velocities I can fine tune the numbers.

The 25/300 military zero is crap. The goal was to produce 300 metre accurate rifles for competitive reasons. The mid range or 2/3 range trajectories with a 25/300 zero are around 8 inches high(above your sight line) at around 200 yards. That's a pretty big difference. This also assumes your optic is 2.25 inches above boreline which for an AR is about right, I could be wrong on that.

TDC
Click to expand...
That is a MAJOR variable factor in the calculation.


For the first zero (first cross point) set at the same distance:
-If you put the optic higher, the cross points will be further apart
but with high in-between POIs.
-Closer the optic is to the bore axis, smaller the height of POIs,
but of course, the distance between cross points will be smaller.

In the software you are using, can you input different
heights for the optics (sights)???
 
Last edited:
Wow! Thanks TDC. I'll have to read this a couple of times (more like 5) to digest all the info. I'll have to measure the distance between my new optic and the bore - it's gonna be higher than 2.5inches though..
 
Yup Kinda....:D

The aimpoint micro will sit lower than the Bushnell but I just measured it and distance from the bore to center of the optic is 5 inches....
Type97review042.jpg
 
You must log in or register to reply here.
Back
Top Bottom