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I sighted in an ar 20in barrel at100yds it shoots 1 to 1-1/2 groups depending on me.
Is it normal for it to be shooting 1to-1/4 low at 40 yds
Failure2Stop
04-30-12, 16:32
Yup, the bullet will be on a rising arc from 2.5" to 3" below line of sight at muzzle (depending on sight height) to your established point of aim/point of impact intersection.
If you are interested, you can check out Zen of the 100 Meter Zero (http://www.f2sconsulting.com/Zen_of_the_100m_Zero.html) for more detail on the 100 meter zero.
Another great thread is this one about different zeros... https://www.m4carbine.net/showthread.php?t=65679
I happen to prefer the 50yd zero for my rifle. In my rifle, with the ammo I shoot, it zeros again at 225 yards. This zero also only puts me an extreme of 2" low to 2" high for every distance out to 250 yards.
Excellent article F2S.
I'll second that, thanks F2S. I've visited your site a few times and somehow missed this...
as soon as I get my stamp from nfa purgatory I will be using the 100 yard zero method compared to what I did in the past. Thanks
Yup, the bullet will be on a rising arc from 2.5" to 3" below line of sight at muzzle (depending on sight height) to your established point of aim/point of impact intersection.
If you are interested, you can check out Zen of the 100 Meter Zero (http://www.f2sconsulting.com/Zen_of_the_100m_Zero.html) for more detail on the 100 meter zero.
F2S, will there be a significant change in holds if using a 10.5" barrel instead of a 16"? I guess I could search for info on this but I figured you could give me a quick simple answer since you have experience with teaching this zero in your class.
I've been using a 50/200 zero with a 2MOA T1 and it has worked well for me out to 100 meters but the 100 zero seems more intuitive. I'd like to take it out to 200 or 300 here soon and I may re-zero and play around with it a bit first...
Failure2Stop
04-30-12, 20:41
F2S, will there be a significant change in holds if using a 10.5" barrel instead of a 16"?
Not significantly until you start getting past 400 meters or so, which, to me, is beyond practical hold-over application in real life. Definately do-able though.
Not significantly until you start getting past 400 meters or so, which, to me, is beyond practical hold-over application in real life. Definately do-able though.
Good to know, thank you!
ridgerunner70
04-30-12, 23:00
Yup, the bullet will be on a rising arc from 2.5" to 3" below line of sight at muzzle (depending on sight height) to your established point of aim/point of impact intersection.
If you are interested, you can check out Zen of the 100 Meter Zero (http://www.f2sconsulting.com/Zen_of_the_100m_Zero.html) for more detail on the 100 meter zero.
Excellent website; I book marked it!
Another good source of information is http://www.handloads.com/calc/
here you can plug in your variables and see the change in data.
Another good source of information is http://www.handloads.com/calc/
here you can plug in your variables and see the change in data.
Never seen this one before, I'm going to have to punch in some data and see what kind of results I get. Thanks for the link
Failure2Stop
05-01-12, 16:53
Never seen this one before, I'm going to have to punch in some data and see what kind of results I get. Thanks for the link
My favorite online ballistic calculator is JBM Ballistics:
http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
I have heard that is the most accurate.
I use strelok on my Android only cause its free.
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My favorite online ballistic calculator is JBM Ballistics:
http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
That one is definitely more detailed, I'll have to play around with it as well.
I tried the one on handloads.com using the following info:
Muzzle Velocity: 2450
Zero: 109.361 (approx. 100m)
BC: 0.243
Weight: 55
SOB: 2.8
Temp: 65.0
Wind: 0
The MV is an approximation of what I had gathered online for M193 out of a 10.5" barrel. After converting the yards to meters, this is the table I ended up with:
http://img441.imageshack.us/img441/8383/75870793.jpg
Looks like there is a huge drop from 200-300, out to 200 isn't terrible. My cousin may have a chronograph, I'd like to nail down the MV and then start hitting targets at those ranges and see what I end up with...
Excuse me Ossifer were you shooting at me, I think your "trazectory" was off did you use a 50yrd zero without confirming at 200?:p
F2S great article. I will probably sight my 3 coming SBRs using your Zen Zero, and keep the 14.5-18" at 50/200 as my brain still functions at 50/200;)
Failure2Stop
05-02-12, 06:27
Looks like there is a huge drop from 200-300, out to 200 isn't terrible. My cousin may have a chronograph, I'd like to nail down the MV and then start hitting targets at those ranges and see what I end up with...
I punched it in JBM just to compare, and it came out pretty similar.
I used my personal median environmental factors, but those really aren't significant at such short distances. (I also dropped the BC to .221 G1 due to the much lower MV)
Anyway, the numbers that are coming back seem like more drop than I recall at those ranges.
**Using a 10.3" gun w/ M855 & Mk262, TA01NSN ACOGs, torso sized targets at 600 meters with a moderate crosswind. M855 was zeroed at 100 meters, required additional hold-off, but not as much as anticipated. Mk262 was zeroed at 300 meters, and required similar hold-off at 600 (can't remember exactly, it was a while ago).
I will probably sight my 3 coming SBRs using your Zen Zero, and keep the 14.5-18" at 50/200 as my brain still functions at 50/200;)
Do whatever you prefer, but one of the reasons I adopted the 100 meter zeroing concept is uniformity across all of my optics. The only thing I do not have a POA/POI 100 meter zero on are iron-sights, for reasons I spelled out. Having everything on the same zero makes life easier. Thaty being said, if you have been using that zero for a long time and are comfortable with precision holds out to 50 meters, you might as well stick with it unless you are willing to give the 100 meter zero application distinct training time.
I punched it in JBM just to compare, and it came out pretty similar.
I used my personal median environmental factors, but those really aren't significant at such short distances. (I also dropped the BC to .221 G1 due to the much lower MV)
Anyway, the numbers that are coming back seem like more drop than I recall at those ranges.
**Using a 10.3" gun w/ M855 & Mk262, TA01NSN ACOGs, torso sized targets at 600 meters with a moderate crosswind. M855 was zeroed at 100 meters, required additional hold-off, but not as much as anticipated. Mk262 was zeroed at 300 meters, and required similar hold-off at 600 (can't remember exactly, it was a while ago).
Hopefully I will be able to re-zero this Saturday and at least get out to 200 meters and see where I'm hitting. IIRC, the lower MV will keep my effective range under 75 unless I use a TSX round or maybe MK318. I have a pile of Mk318 laying around that I keep loaded up, I'll have to get it out and see how close it is to the M193.
I'm having trouble finding muzzle velocities for MK318 and MK262 out of a 10.5" barrel. Would I see a significant POI shift at 100/200 meters?
And thank you for taking the time to punch that info into JBM BTW...I've haven't done much long range shooting or even really paid attention to hold overs because I've been working inside 75 meters for the most part...I need to do a little research to understand what a lot of those variables are...
Do whatever you prefer, but one of the reasons I adopted the 100 meter zeroing concept is uniformity across all of my optics. The only thing I do not have a POA/POI 100 meter zero on are iron-sights, for reasons I spelled out. Having everything on the same zero makes life easier. Thaty being said, if you have been using that zero for a long time and are comfortable with precision holds out to 50 meters, you might as well stick with it unless you are willing to give the 100 meter zero application distinct training time.
I would prefer all to be the same across the board as well, but will use the 100 for the SBRs for that "distinct training time" until I can decide which one my mind works best with. IIRC Paul Howe prefers the 100 also.
Failure2Stop
05-04-12, 11:17
I'm having trouble finding muzzle velocities for MK318 and MK262 out of a 10.5" barrel. Would I see a significant POI shift at 100/200 meters?
I have had all kinds of different shifts when changing ammo, from a simple lot change that resulted in a 3-4 MOA shift, to changing from Mk262 to M193 that was still dead on at 200 meters, to a 9 MOA difference between Mk262 and M855.
Generally I will zero with my precision ammo and compare it to my bulk ammo at 100. Generally I will only see a 1 to 2 MOA shift, which is fine for inside 50. The shift is not predictable between ammo even of similar classification, though it is repeatable within that lot.
The only way to be sure of shift is to do a zero confirmation.
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Failure2Stop
05-04-12, 11:20
I would prefer all to be the same across the board as well, but will use the 100 for the SBRs for that "distinct training time" until I can decide which one my mind works best with. IIRC Paul Howe prefers the 100 also.
Makes sense.
One note, last I heard, Mr Howe zeroes 3" high at 100. I believe this is due to his preference for iron sights, which is similar to my thoughts on iron sight zero, but I cannot speak for him.
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One note, last I heard, Mr Howe zeroes 3" high at 100.
so, about a 250 yd zero.
Makes sense.
One note, last I heard, Mr Howe zeroes 3" high at 100. I believe this is due to his preference for iron sights, which is similar to my thoughts on iron sight zero, but I cannot speak for him.
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Like you and Howe I zero all my irons a bit high (rifle and pistol) about 2" high so I can see more of what I am shooting at... due to the eyes I am actually experimenting with different 6 O'Clock holds that the Camp Perry guys have been schooling me on for sight in purposes.
Got a good solid zero at 100 today with the Aimpoint. I still need to tweak the irons a little though. I'm using KAC Mircos with the 200-600 rear so I may zero at 100 with the Z setting and see where I hit at the other settings...
I was averaging about 1.5-1.6" 5-round groups with Federal XM193, shooting prone off of a ruck which was a little better than I had hoped.
I can get out to 186 meters in my back yard. I may setup a target at that distance on Wednesday and hit it with the same XM193 and some Federal MK318. If I take it out that far, I will be shooting uphill approx. 20 degrees. Not sure hot much that will affect my drop.
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