50/200 or 100 yard zero?

[nickdrak]

Some folks' definition "basically" is pretty sloppy. My 50yd zero results in a far zero of 205m (224yd).

My question is this: How would the OP changing co-witness methods in any way affect the impact of the round? With either absolute or lower-1/3, you're still lining up the irons and the dot at the same sight height and presumably putting the same zero on each. The only difference is the height of the optic itself, which doesn't matter with an RDS.

Am I missing something, or is the OP somehow doing something different that's inducing the results he's seeing?

The only real difference will be the higher "Height over Bore" with the optic from 0 yards out to about 15 yards. So at those closer distances, you will need to compensate for more "Off-set" with the optic set-up with a "Lower 1/3" co-witness than what your iron sights will have. It will also have a very slight difference in your "point of impact" at 25, 50, 75 yards compared to your iron sights up-to your actual "Point of Aim/Point of Impact" (Zero).

[Robb Jensen]

I use a 200yds zero for my 3gun rifles. (start at 25yds getting it hitting 1.5" low, then move to 50yds get it hitting POA/POI then go to 200yds getting it hitting POA/POI). My 3gun rifles with a 50yd POA/POI zero hits about 2.5-3" high at 200yds. But when I adjust it for correct POA/POI at 200yds the 50yd zero is barely changed.

On my SBRs I use a 100yds zero when I get the chance otherwise it's a 50yd POA/POI zero.

[Belmont31R]

A 50 yard zero will give you less deviation from LOS out to 250 than 100 yard zero will. I just went through my photobucket and deleted all the graphs I had but I "mapped" out a few different zeros, and with a 50 yard zero your POI will be within the dot from about 30 yards to 230/240 yards. Depends on the ammo, barrel length, dot size, etc. I did it for my basic setup which is a 16" barrel with a 4MOA dot shooting 77 grain ammo at 2700FPS. With a 4 MOA dot at 250 yards the dot covers 10" which is well within the POI.



They are pretty close though. Doesn't really make too much of a difference in all honesty. The 223/556 is flat shooting enough you only really need to start holding over once you get out to about 300 yards. This round tends to start dropping at a good clip around 250 yards, and is pretty predictable out to about 450/500. Past that you need to be doing some really good shooting to make consistent hits. The light bullets don't do good in wind, and they lose energy fast. Plus most people are using regular ole CL barrels with mil type ammo which isn't the most accurate combo in the world. On a LaRue steel target @ 250 yards with just a T1, and a 16" CHF barrel I can hit it about 50% of the time just pop shooting, and the last time I did that they had painted the target orange against a brown/red dirt berm with the sun setting casting shadows so I could barely see it at all.

So yeah either way you go (50 or 100 yard zero) you will be fine. Theres not a whole lot of distinction between the two. What you don't want to do is zero it for a real close distance like 25 yards or shorter. Just remember at indoor distances your POI will 2" or so below your POA. I was taught to "aim" for the center line at the base of the throat at CQB distances. This will drop your rounds into the upper torso around the breast plate.

[jhs1969]

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jhs1969,

If you have't seen the info in the Link to the Thread below, take a look, it is recent, very informative and may answer your questions.

Easy way to zero your rifle

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Thanks for the link, found the charts I was looking for there. Thanks again.

[jhs1969]

I set my rifle at a hard 50 yard zero, the 200 yard zero falls closer to 230. Ammo was plain old PMC 55 gr. FMJ, rifle set up with 2 moa Aimpoint, 16 " midlength.

I understand your question about group size at 200. If your group at 200 is say 6-7" how can you verify the zero? Is that your point?

No, my point is that my 100yd impacts now seem to be higher than before.

[jhs1969]

I think I may have induced some confusion, sorry if I have. As I said ealier I have used an ARMS mount for several years, it was an absolute co-witness with my irons. I recently switched to a Larue with a lower 1/3 co-witness. I had a good feel with the ARMS set up and a 50yd zero. I had built my confidence with my close range hold overs and was satisfied with my 100 and 200yd impact points. And now with the higher mount (1/3 co-witness), I've got some concerns about my 100yd impacts (the impacts are higher than before). I've killed several varmits in the 50 to 100yd range but now I'm a little worried the higher 100yd impacts will effect my ability hit these smallish critters in the above ranges. This is why I'm considering going to a 100yd zero, although I'm not going to make any hard changes until I can get in a good solid range session.

Jay, I'm begining to develop the same opinion.

Please keep the opinions coming, they do help.

[ST911]

Merits and liabilities of zero distance notwithstanding...

One of the most often overlooked variables in the question of zero is shooter ability. More than which distance to zero at, ask: At what range can the shooter place rounds on target with sufficient accuracy and consistency to determine what the true zero of the gun is?

50yds is a reasonable distance for the majority of shooters, and one at which even the lowest common denominator can be successful. 100yds will be a stretch for many. One can always use a reduced distance with POI adjustments, but real and true zero isn't found until it's verified at actual distance.

Food for thought.