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Centerfire Rifles - Semiautomatic or Gas Operated Centerfire rifles, carbines and other gas operated rifles.

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  #1  
Old 11-13-2007, 9:18 AM
EricCartmann EricCartmann is offline
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Default Bullet Drop of .223 and .308 Discussion.

Not trying to get into too much detail (such as FPS, barrel length, bullet weight, ballistic coeffecient, temperature, altitude, humidity, or rifle type). Not going for precision, just need a general idea where things stand.

So say you just pick up a .308 and .223 and start blasting down range. On average what do you think the bullet drop will be?

Here is a Chart I came up with:

.308

100yards Zero
200 -5" (as in negative 5 inches from POA(point of aim) at 100 yard zero).
300 -15
400 -35
500 -65
600 -110
700 -160
800 -240



.223

100yards Zero
200 -3" inches
300 -10
400 -25
500 -50
600 -75
700 -115
800 -170

What do you think of this chart? Is it inline with what you are getting with your particuliar rifle, your particuliar barrel length, and your particuliar bullet weight?

Last edited by EricCartmann; 11-13-2007 at 9:21 AM..
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  #2  
Old 11-13-2007, 9:27 AM
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This ballistic program (online & free) will give you a pretty close chart for anyone's rifle.

http://www.eskimo.com/~jbm/ballistics/traj/traj.html
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  #3  
Old 11-13-2007, 9:40 AM
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Temperature, Wind, Elevation, Humidity, Angle will all change the BDC.

IMHO unless in competition you will not need to take a shot at more than 200 yards in Defensive situations or 400 yards in Hunting situations.

Last edited by glockman19; 11-13-2007 at 9:43 AM..
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Old 11-13-2007, 9:59 AM
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glockman, just curious if those bullets were out of a particuliar rifle and barrel length, or are those just the general numbers you have for all your rifles?
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Old 11-13-2007, 10:05 AM
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barrel length and bullet type matters alot!
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Old 11-13-2007, 10:20 AM
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Here is an example. I had a load developed using 45.5g of RL14 behind a 155g Scenar load for my Savage with a 1-10 twist barrel and 24" long. The same load in my 700 with a 22.25" barrel and a 1-12 twist ran 2800 fps. It took almost a grain to get the velocities up. This changed my drop table by a bit. My 500 yard come ups is 9.5 minutes for my load running at 2900 fps. The load running at 2800 was 10.25 minutes.

That would be the difference from a hit to a miss. 1 MOA is roughly 5 in at 500 yards so I would have been off almost 4 in.
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Old 11-13-2007, 10:21 AM
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Quote:
Originally Posted by jandmtv View Post
barrel length and bullet type matters alot!
More than most realize. Different bullets behave very differently. Start at the JBM site and play around a bit.
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Old 11-13-2007, 10:25 AM
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Here is a quick table for federal gold medal 168g ammo. Assuming optimal conditions and sea level.

MOA valuse

50 -.25
100 0
200 2.25
300 5.25
400 8.75
500 12.50
600 17.00
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  #9  
Old 11-13-2007, 10:28 AM
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Quote:
Originally Posted by EricCartmann View Post
Not trying to get into too much detail (such as FPS, barrel length, bullet weight, ballistic coeffecient, temperature, altitude, humidity, or rifle type). Not going for precision, just need a general idea where things stand.
Thats like saying, "Not to get into detail about engine size, weight, etc...how fast does a car go?"

There are too many variables for a general idea.
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Old 11-13-2007, 10:52 AM
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The .223 ammo I used yesterday shot 1.3 mils lower than the one I used last week.

Both were 55gr FMJ.

Same rifle and nearly identical conditions.

Convert that to moa and inches at 600yds and you'll see how much of a difference it makes.
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  #11  
Old 11-13-2007, 10:59 AM
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I know but in general you can say Cars go about 120 mph for top speed. This is what I am trying to figure out here.

I have found that with my chart it comes very close, and you will only have to make little adjustments for rifle type, barrel length, and rifle type.

I agree with what you guys say about it makes a huge difference between bullet type (such as boat tail), weight, and barrel length. But like I said, I am just trying to find a very rough average number.

Also, I was thinking more in line with the BDC on ACOGs calibrated for .308. I wonder what barrel length, and ammo was used for the .308 ACOG? I believe the .223 ACOG BDC on a NSN is calibrated for a 55gr bullet out of a 14.5" barrel. And my TA11F is for a 55 gr bullet out of a 16" barrel.

For .223 I have found that M855 or M193, both are almost dead center out to 300 yards, at most there will be a 4" difference at the extremes of high and low.

Last edited by EricCartmann; 11-13-2007 at 11:04 AM..
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  #12  
Old 11-13-2007, 10:59 AM
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1 mil is 3.6 inch at 100 yards if I recall.
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Old 11-13-2007, 11:02 AM
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Quote:
Originally Posted by uclaplinker View Post
The .223 ammo I used yesterday shot 1.3 mils lower than the one I used last week.
1.3 mils at 600 only due to weather?
That's like 27" or so.
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  #14  
Old 11-13-2007, 11:03 AM
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Quote:
Originally Posted by Prc329 View Post
Here is a quick table for federal gold medal 168g ammo. Assuming optimal conditions and sea level.

MOA valuse

50 -.25
100 0
200 2.25
300 5.25
400 8.75
500 12.50
600 17.00

I shot this past weekend 40 rounds of Federal Gold Medal Match and found those numbers in line for what I did with my 22" M1A, clear day, about 70 degrees, no humidity and about 2500 ft above sea level.

Last edited by EricCartmann; 11-13-2007 at 11:27 AM..
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  #15  
Old 11-13-2007, 11:03 AM
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Quote:
Originally Posted by EricCartmann View Post
Also, I was thinking more in line with the BDC on ACOGs calibrated for .308. I wonder what barrel length, and ammo was used for the .308 ACOG? I believe the .223 ACOG BDC on a NSN is calibrated for a 55gr bullet out of a 14.5" barrel. And my TA11F is for a 55 gr bullet out of a 16" barrel.

For .223 I have found that M855 or M193, it is only about a 4" difference out to 300 yards.
Pure speculation but I believe they use an M14 to determine BDC.
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Old 11-13-2007, 11:04 AM
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Quote:
Originally Posted by EricCartmann View Post
I believe the .223 ACOG BDC on a NSN is calibrated for a 55gr bullet out of a 14.5" barrel.
The NSN is setup for 62gr M855 from a 14.5" M4 barrel.
Using 55gr bullets, you will want them to be going about 2950fps from any barrel length for the NSN to work properly.
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  #17  
Old 11-13-2007, 11:10 AM
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Quote:
Originally Posted by Prc329 View Post
Pure speculation but I believe they use an M14 to determine BDC.
Now thats funny because ACOGs are pretty much useless on a M14. Instead of a cheek weld you will have a boob weld

Last edited by EricCartmann; 11-13-2007 at 11:16 AM..
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  #18  
Old 11-13-2007, 11:14 AM
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Quote:
Originally Posted by ar15barrels View Post
The NSN is setup for 62gr M855 from a 14.5" M4 barrel.
Using 55gr bullets, you will want them to be going about 2950fps from any barrel length for the NSN to work properly.
Where do we get info for ACOGs and how they are calibrated for what barrel length and what ammo? The Trijicon website is pretty lame. All it says is for the TA11F is "calibrated for .223 flat top rifles"
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  #19  
Old 11-13-2007, 11:17 AM
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I know but that is the only thing I can think of in the military that would use a 308. I don't see an acog on a bolt gun or may CQB AR10s in use.

One interesting thing from the site is they offer an LAPD reticle in the 4x acog. I would think if you knew what the LAPD is running as far as ammo and if they are m4, etc that could be useful to find out.
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Old 11-13-2007, 11:43 AM
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Quote:
Originally Posted by EricCartmann View Post
Where do we get info for ACOGs and how they are calibrated for what barrel length and what ammo? The Trijicon website is pretty lame. All it says is for the TA11F is "calibrated for .223 flat top rifles"
You have to call Trijicon and talk to them.

Think in military terms.
A "rifle" has a 20" barrel.
A "carbine" has a 14.5" barrel.
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  #21  
Old 11-13-2007, 11:50 AM
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Quote:
Originally Posted by EricCartmann View Post
Where do we get info for ACOGs and how they are calibrated for what barrel length and what ammo? The Trijicon website is pretty lame. All it says is for the TA11F is "calibrated for .223 flat top rifles"
I found this on Trijicon's website in their FAQ in a minute or so:

Quote:
03. What bullet was used to calibrate the ACOG scopes? The TA01, TA11, & TA31 (.223) were designed for the 5.56mm, 20 inch barrel, 55 grain bullet, and M16/AR15 carry handle mount. The TA01B & TA11C(.308) were designed for the 7.62mm, 20 inch barrel, 168 grain bullet, and M16/AR15 carry handle mount. The TA01NSN was designed specifically for the US Special Operations Command SOPMOD M4 Carbine. To meet their requirements, the reticle bullet drop compensator and range finding stadia lines were based on the trajectory of the 62 grain bullet from a 14.5 inch barrel, flattop mount (Picatinny rail Mil.Std.1913).
Linkage: http://www.trijicon.com/faq.cfm#f21
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  #22  
Old 11-13-2007, 12:01 PM
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Quote:
Originally Posted by pidooma View Post
I found this on Trijicon's website in their FAQ in a minute or so:

Linkage: http://www.trijicon.com/faq.cfm#f21
cool thanks.

I have found that for 300 yards or less... 14.5", 16", 55gr, 62 gr, the results are almost neglible.
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Old 11-13-2007, 4:36 PM
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No no, 1.3 mils due to ammunition. Nearly identical weather conditions (temp and wind).

I switched from a hot 5.56 load to a cheap .223. It was like night and day. At 600 yards I had to hold over 1.3 mils more than the previous week.


Quote:
Originally Posted by ar15barrels View Post
1.3 mils at 600 only due to weather?
That's like 27" or so.
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Old 11-14-2007, 3:20 PM
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The tables you posted at the top, at least the 308 one, is close enough for hip pocket purposes for 147grFMJ or 168, 175gr match in 308/30-06. I don't put a lot of stock in ballistic calculators. They're good for getting on paper, and for comparing load A vs load B. But for hitting the center of a target, it's a poor substitute for actual trigger time data.
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Old 11-14-2007, 11:52 PM
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Do you guys really zero your rifles at 100 yards?

I'm not saying that's wrong and if it works for you great. I zero at 200 there's less hold over at longer range and just a bit high at 100.
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Old 11-15-2007, 7:57 AM
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well, close enough for hip pocket purposes , and in less time than it takes to type this you can check his ballistic program (online & free) will give you a pretty close chart for anyone's rifle.

http://www.eskimo.com/~jbm/ballistics/traj/traj.html

And of course the right way is to go a shootin and keep a log
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Old 11-15-2007, 8:47 AM
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Quote:
Originally Posted by randy View Post
Do you guys really zero your rifles at 100 yards?

I'm not saying that's wrong and if it works for you great. I zero at 200 there's less hold over at longer range and just a bit high at 100.
The guys that do the 1000 yards stuff zero at 600 yards. For me 100 yards is good enough because:
- 100 yards is easy to walk, set up targets, and zero. I can still see the bullet holes with 7x binoculars to make adjustments at 100 yards. 600 yards is too far to walk and you have to go downrange to check the target.
- 90% of small arms exchanges occurs at 50 yards or less, so basically my rifle is battle ready.
- With a 100 yard zero, in general you are only about the size of a 1 to 1.5human head to low at 300 yards. And the size of 1 to 1.5 full size human man too low at 600 yards. This is close enough for me.

A 200 yard zero is not much different than zero'ing at 100 yards. For an AR you can just zero 1.5" below POA at 100 yards and count on another 3" in drop for 200, and that there is a 200 yard zero.... and I just saved you 100 yards in walking distance.
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  #28  
Old 11-15-2007, 10:36 AM
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I shoot to 1000 yards and zero at 100. Most shooters do the same.

When shooting at distance, the difference between having a 200 yard zero over a 100 yard zero is negligible, especially at 600 and beyond.
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