Riddle Me This

[No Bananas]

Big question: (sorry I'm new to this). If I have my Aimpoint zeroed at 50 yds. When I go to shoot a pop can or what have you, at a closer distance (like 25 yds.) do I am higher or lower than the object?

[jmart]

Bullet will impact lower than point of aim.

[Failure2Stop]

Go to this site-
JBM Small Arms Ballistics- Trajectory (Simplified)

Under Ballistic Coefficient, plug in "0.243" (make sure it says "G1" to the right)
Bullet weight- "55", "gr" to the right
Caliber- "0.224", "in" to the right

Muzzle Velocity- "3125", make sure it says "ft/s" to the right.
Sight height- "2.8", "in" to the right

Under "Maximum Range" change it to "300" unless you really care about longer ranges
Change "Range Increment" to "5"
Set "Zero Range" to "50"

Go to the bottom and click on "calculate".

This will tell you approximately what your trajectory path will look like with M193 from a 16" barrel at close to mid range. Playing around with your temperature and elevation will make some slight differences at long range, but nothing at sub-100 yards.

[RD62]

Failure2Stop,

Thanks for the link! That's very useful!

I was at the range today, zeroing my new BCM Middy build and trying to decide what range to zero at. I don't have a chrony, so your velocity numbers are very helpful in seeing how various zeros affect hold-over or under at various ranges.

Would you happen to have any velocity numbers for a 10.5" with M193?

Thanks!

-RD62

[No Bananas]

PPU M193 (55 gr.)

10.5" LMT: 2749 FPS

12.5" GTS Operator Barrel: 2932 FPS

And here are some extras:

American Eagle 55 Gr. .223

10.5" LMT: 2633 FPS

PMC 55 gr. FMJBT .223

10.5" LMT: 2514 FPS

Black Hills 75 gr MHP

10.5" LMT: 2371 FPS

Win 5.56 Q3131 (55 gr.)

10.5" LMT: 2862 FPS

12.5" GTS Operator Barrel: 3007 FPS Pretty fast for an SBR This is an average of 50 rounds. The highest velocity was 3096!

BTW: I'm very jealous of the BCM Middy ... I want one!

[Failure2Stop]

If you aren't set on a zero yet I highly recommend a 100 yard zero.
It is very applicable for distances relevant to an SBR/Red Dot.
It provides a very gentle upward slope which makes for easier and less drastic offset at close range and reaches out past 200 yards effectively.

NoBananas- good info on commercial ammo.

[RD62]

PPU M193 (55 gr.)

10.5" LMT: 2749 FPS

12.5" GTS Operator Barrel: 2932 FPS

And here are some extras:

American Eagle 55 Gr. .223

10.5" LMT: 2633 FPS

PMC 55 gr. FMJBT .223

10.5" LMT: 2514 FPS

Black Hills 75 gr MHP

10.5" LMT: 2371 FPS

Win 5.56 Q3131 (55 gr.)

10.5" LMT: 2862 FPS

12.5" GTS Operator Barrel: 3007 FPS Pretty fast for an SBR This is an average of 50 rounds. The highest velocity was 3096!

BTW: I'm very jealous of the BCM Middy ... I want one!

Thanks! I've saved this info!

I'll have to try and get some pics up of the Middy. This was her first time out.

Just to gloat a little, she runs a BCM F/A BCG too! She's saweeett!!

-RD62

[RD62]

If you aren't set on a zero yet I highly recommend a 100 yard zero.
It is very applicable for distances relevant to an SBR/Red Dot.
It provides a very gentle upward slope which makes for easier and less drastic offset at close range and reaches out past 200 yards effectively.

NoBananas- good info on commercial ammo.

Thanks F2S. I was going for a 100yd on the Middy, but was wondering if a closer zero wouldn't be more appropriate for the SBR. I was thinking 50yds for the SBR. Using your calculator above that keeps impact within 2" above or below POA from 10-200yds. Which would seem to be about what I'd get from a 100yd zero from the 16" Middy using the same M193 per the velocity numbers you posted above. What do ya think?

-RD62

[jmart]

If you aren't set on a zero yet I highly recommend a 100 yard zero.
It is very applicable for distances relevant to an SBR/Red Dot.
It provides a very gentle upward slope which makes for easier and less drastic offset at close range and reaches out past 200 yards effectively.

NoBananas- good info on commercial ammo.

???

The gentler slope increases the offset issue, but makes things down range simpler.

The steeper rise angle of the 50 yard zero decreases offset. How much I'm not sure, but since the rise angle is steeper, the POA is converging with the POI sooner.

Theoretically, if you wanted to eliminate short range offset entirely, just sight your weapon in for 10-15-20 yards or so. Short range POI and POA would be the same, but the rise angle would make things so bizarre out past your sighting in distance that "holding under" would be very problemmatic when you are out to 500, 100, 150 yards.

[Failure2Stop]

???

The gentler slope increases the offset issue, but makes things down range simpler.

The steeper rise angle of the 50 yard zero decreases offset. How much I'm not sure, but since the rise angle is steeper, the POA is converging with the POI sooner.

Theoretically, if you wanted to eliminate short range offset entirely, just sight your weapon in for 10-15-20 yards or so. Short range POI and POA would be the same, but the rise angle would make things so bizarre out past your sighting in distance that "holding under" would be very problemmatic when you are out to 500, 100, 150 yards.

You're missing my point.
The difference between offset hold-over between 5 and 25 yards will be much less than with a say 25 yard zero. With a 100 yard zero the amount of difference in my hold over between the 5 and 25 is about 1 inch, whereas with a 25 yard zero the difference is about 2.6 inches. There is just less to have to think about, which is nice when you are trying to shoot someone in the head that is trying to kill you at close range with bullets. The 50/200 falls roughly between the 25 and 100 zeroes, but it still takes more consideration than the 100 does.