Comparing ballistics of 55gr and 75gr 223 at 500-600 yards - drop is close?
Looking to stretch out to 500-700 yards with one of my AR's.
Will be using 75gr loads and a 20in barrel.
[update] barrel twist 1/9 (this one shoots the 75gr just fine) although I have another 20in upper with 1/7 barrel
Plugging these numbers into a ballistics chart I use
(1)55gr BC = .243, MV = 3240fps (Privi 55gr)
drop at 500 = 54in
drop at 600 = 96in
drop at 700 = 160in
(2)75gr BC = .395, MV = 2750fps (Privi 75gr)
drop at 500 = 60in
drop at 600 = 100in
drop at 700 = 155in
So it seems elevation adjustments would be "close" to within 3-5 inches, good enough for steel target shooting, not so much for gophers and such.
This is good, because I plan on getting a Leupold Mark AR 3-9x40 mildot, and the elevation cam is set for 55gr loads.
Seems I should be good to go for targets out to 700?
The more "noticeable" difference is in the windage adjustment, which would be expected for the different bullet weights.
I'm surprised the elevation drop is so close
Are my numbers off?
Barrel twist? Or did I miss it?
What 55gr bullet/load are you planning on shooting? Dont plan on any reasonable accuracy with 55gr FMJ at 700 yards. Drop may be close, wind will be a big factor at that distance.
Updated with more info. Dont plan on using the 55gr past 500, just plugging in the numbers to see how the elevation cam would match either load.
You forget the 4 feet additional wind drift, roughly.
With program it should be fine. As long as you didn't put crap information in.
Make sure you use proper BC, verify with actual shooting.
Based on magazine articles on this subject I'd recommend sighting in with the heavier bullet if not continually changing settings on scope based on shot records for different rounds.
1/9 you are lucky it is one that shoots 75s good. YMMV with other barrels.
You'd be pretty lucky to shoot both at such long range with significant accurracy in both rounds.
1/7 was made that fast to stabilize tracer rounds that are harder to stabilize.
That much twist makes it easy to spin a 40 grainer apart.
Originally Posted By RedFalconBill:
You forget the 4 feet additional wind drift, roughly.
Maybe it was after the edit I dont know but he said
Originally Posted By Eastwood123:
The more "noticeable" difference is in the windage adjustment, which would be expected for the different bullet weights.
I'm surprised the elevation drop is so close
Originally Posted By Eastwood123:Are my numbers off?
Probably not. The wind is the big deal. SInce drop is a known factor it doesnt bother us as much as wind usually.
drop is nothing... wind is the bitch....
