AR: 14.5''-20'' Bullet drop difference?

SuperDave

SuperDave

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I am thinking of buying a second hand ACOG sight for a 20'' barrelled AR15.

Unfortunately, the ACOG's bullet drop compensating reticle is designed for a 14.5'' barreled rifle.

So I am wondering if the bullet drop difference between a 14.5'' and 20'' AR is significant or not.

14.5'' and 20'' AR owners, what bullet drops do you get at let's say 400 meters with a 62 grains bullet?
 
Most ACOGs used a 16.1" barrel to run the BDC therby splitting the difference between 14.5" and 20". There are one or two models which are m4 specific...which one are you thinking of getting?
 
I'm looking at a TA31RCO-M4CP right now but any TA31's would do. According to trijicon's website it's 14.5 but whatever. The TA31RCO-A4CP's seems harder to find.
 
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Remember this is all about velocity differences. Just check into that. 50 fps is supposedly good for 1MOA. I don't know the data on the barrels, though.
 
This will get ya in the ball park.

The M4 = 14.5" barrel.
The M16 = 20" barrel.


BallisticsA.gif




BallisticsB.gif




BallisticsC.gif
 
Strabismo said:
I'm looking at a TA31RCO-M4CP right now but any TA31's would do. According to trijicon's website it's 14.5 but whatever. The TA31RCO-A4CP's seems harder to find.
Click to expand...

RCO was one that was specifically for the 14.5", it was for that reason I didn't go for it, I like the flexability of the NSN or TA31 models which were done with 16.1" barrel as I like to go from 14.5" to 20".
 
Thanks smack daddy. That means that the difference is about 1.25 MOA at 400 yards, about the 1/4 of the horizontal 400 meters line in the reticle. I think I'l have to search for a A4 one on Ebay or for a TA31.

Fragmentation threshold is the maximum distance where the bullet will go fast enough to fragment in the target causing significantly severe wounds. Past that distance, it won't fragment and won't cause much damage.
 
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Interesting chart produced by Smak - thanks for sharing. One can see that you're losing a fair bit of effective performance (fragmentation threshold) by going to a shorter barrel.:eek: Anywhere from 40 to 80 yards depending on bullet wt by dropping from a 20 inch to a 14.5 inch. For the military people that's a quite a difference. One can see that as a police/civilian shooter with no real ammo restrictions you're far better off to use the hunting soft point ammo (eg 64 gr ww power point) which should expand reliably over 2200 fps provided of course your rifle reliably feeds them.
 
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