3-Gun Rifle Sight-In/Hold-Under Suggestions?

[Kor]

Hey, all - my current favorite evil black rifle is an Armalite AR-180B, which handles fast and shoots nicely in the close-range stages. However, I'm having an "operator headspace & timing" problem shooting the "long-range stage" at the club matches I shoot, which is usually set up with a mix of close-range cardboard targets and steel plates from 50-200yds.

I already know I'm supposed to line up the front sight ABOVE the rear peep for the close-range cardboard, because the bullet is traveling below the line of sight that close to the muzzle - I just have to keep drilling that little factoid into my thick noggin. I STILL find myself looking through the peep for the front sight, though.

From 75-200yds, the steel targets are nice big gongs, either 16" squares or steel IPSC silhouettes, and they don't give me too much trouble. What really gets my goat are the 6" "lollipop" targets that they set up at 50yds, which bob around on fiberglass poles after you hit them once(and which you have to shoot TWICE, natch). Even when I call the shot as good, I still can't seem to wrap my mind around the bullet's trajectory at 50yds.

Okay, here's the technical details:
- AR180B rifle has a 18" barrel with 2" of muzzle brake, 1/9" twist.
- Ammo is 55gr milsurp-equivalent, Winchester or South African PMP.
- Sights are, for practical intents/purposes, M16A1-type(elevation-adjustable front, windage-only-adjustable rear, 2-position flip-peeps), 19.5" sight radius. FYI, I'm currently using Trijicon iron sights, with a slightly thicker, tritium-enhanced front sight blade instead of a GI-type post.
- Current zero is about 4" high at 200yds Known Distance(6-o'clock hold on 8" steel plate), using the small 200yd+ aperture.
- The ballistic charts all say the bullet should still be within 2" of line-of-sight all the way out to around 250yds, but you couldn't tell that by the way I seem to shoot...

Any 3-gunners or Action Rifle shooters got any suggestions on how I should zero my rifle so I can engage steel from 50-200yds with as little adjustment as possible between targets at different ranges? Or should I keep my zero as I have it, and learn to hold-under on the 50-yd steel?

Thanks in advance!

 

[lmccrock]

You might post a question in the 3-Gun/IPSC Rifle section of the Brian Enos Forums.

Current zero is about 4" high at 200yds

Ok, where is the "zero"? To me, "zero" is where the POI and POA are the same. Maybe I am using the term wrong.

There really are 2 zeroes: first is close where the bullet trajectory crosses the sightline on the way up, then again on the way down. My 3-gun rifle (20" AR with compensator) is zeroed at 50 yards, and about 1-2" high at 100 yards. I have not checked it farther out, but the trajectory should cross the sightline again around 200-250 yards. So it is on steel out that far, and in an IPSC A-zone as well. Unless you are shooting 350-400 yard targets, the 50 yard zero works well for 3-gun.

With different brands of 55 gr FMJ, the POI have shifted up to 1", and that is at 50 yards.

By the way, I tested some 68 gr Black Hills and it was about 7" high and 4" left from my 55 gr zero at 100 yards. My highpower rifle shifts POI between these loads about 2" but a net shift of 8" was more than I expected from this gun. So, be careful switching ammo.

Lee

 

[Correia]

I'm an avid 3gunner, but this is going to sound pretty weak. Aim for the middle!

Seriously, 4 inches high at 200 sounds pretty horrid. I sight in so that I am hitting a couple inches high at 100, and then all I need to do is hold onto the center of any target at any range out to 200 yards and get a hit. I figure in 3gun you don't have time to mess around with figuring out the exact range, and then shooting a pretty group.

And I've seen this with lots of shooters, you can figure out the ballistics of you cartridge perfectly, 1 inch high at this range, 2 at that, 3 low at that. And you can have that in your head, and that will even work just fine at the range. But when you are shooting a stage with targets from close up to far away at hyperspeed, you don't have time to THINK about your trajectory.

I see this often. You will have a stage with close, medium, and far targets. When you score them, the close and far targets are fine, and the medium targets are down lots of points. I think the key to getting over this is just practicing a lot, and getting to the point that when you see the target, where you put the front sight is instinct.

 

[BillL223]

My zero is 200 yds. This is about 1-2" high @ 100 and right on @ 50. For the close shots, I aim through the sights at the very top of the upper A/B zone.

 

["yote"]

Get rid of that 6 o'clock hold aiming. It has no place in rifle shooting.
mavbe for handguns ( I still don't like it there either ) but not rifles.
Assuming that your 55 FMJ is going approx 3200 fps then at:

50 yds - .50 in high

100 yds - 1.5 in high

150 yds - 1.3 in high

200 yds - Zero point

Go out and zero it 1.5 in high at 100 yds and try that.

 

[Correia]

I should point out that when I say "a couple inches high" at 100, I won't give an exact number because I have 3 gunned with .308, 7.62x39, and .223. So it depends.