Zeroing an M4 look-alike

ghanderson10 · Feb 20, 2009

I've got a bunch of 25m military 300m zero targets for the M4, but how much of a difference does the extra 1.5 inches make?

Also, does anyone know if I could use them to zero an AK for 300 meters? :huh:

(I hope this post is confusing enough)

JumpWing · Feb 20, 2009

ghanderson10 said:
(I hope this post is confusing enough)

Yes, it is.

You have a bunch of 25-meter military 300-meter zero targets... and there's a 1.5 inch difference between those targets and... what?

Spray-n-pray · Feb 20, 2009

If you are talking about the difference between meters and yards, one meter is 3 1/4" longer than a yard. That won't affect you much at 25m, but at 300m it starts adding up. At that range, the extra inches add an extra 81' 3", or roughly 27 yards. That shouldn't affect bullet drop too much until you are out past 300m, but you would have to check the specific ballistics for the ammo you are using to determine that. This probably isn't even what you were asking, but I hope you enjoyed reading it as much as I did typing it.

bnr32gtr · Feb 20, 2009

JumpWing said:
Yes, it is.

You have a bunch of 25-meter military 300-meter zero targets... and there's a 1.5 inch difference between those targets and... what?

I believe he is talking barrel length, not target size. He's comparing his 16" barrel to his issued M4 with the difference a barrel measuring 14.5" in total length.

What ammo are you sighting in with? Sight in with the bullet weight you will be shooting most. If you send 55gr down range, sight in with that. If it's 62gr, sight in with it, instead. Just try not to deviate. I have no numbers to reference at the moment but I do have a small bit of experience that tells me bullet weight and barrel twist do account for something.

I recommend bore sighting, then take to the range to do your sight in. Will save you LOTs of time and money.

Good luck!

ghanderson10 · Feb 20, 2009

Thanks for the advice, bnr. Do you have any idea how much a bore sight would run? I've had minimal experience with the borelight, but I imagine it wouldn't be cheap.

As far as the length of the barrel goes, I'm pretty much wondering if shooting milspec rounds at a military zero target with a non-milspec (i.e. longer barreled) M4 will require too much of a change in procedure... Simply put, I'm wondering if I can still do it at an infantry level of complication

To (finally) explain the whole 25m 300m zero, the military sights in personal weapons for 300m, but does so on a 25m range. The rifle is grouped and zeroed on a target made to simulate the actual 300m target on the qualification range. Sounds weird, but it's not bad. Besides, think about having to walk 300m to check your shot patterns : P

Buddhalux · Feb 21, 2009

Don't forget when you're zeroing at 25m to adjust your rear sight elevation to the 8/3 line.

ghanderson10 · Feb 21, 2009

Then one click to the right (up) afterward, correct?

JumpWing · Feb 21, 2009

I always understood that M4s and their cousins are best zeroed at 200m.

ghanderson10 · Feb 21, 2009

I have no idea if that's the best way to do it or not...but all our personal weapons are zeroed for 300m, as that's the distance of the furthest target on the qual. range. The M4 zero target has slightly different calculations than the M16 target due to the different ballistics, but as far as I know, the calculations only matter when making windage and elevation adjustments.

One of the biggest areas of concern for me is this: My XM15 has a 16" barrel, which is 1.5" longer than the M4, and 4" shorter than the M16.
The differences between these three rifles lead me to ask the question in my first post... Should I try to zero my weapon at slightly below center-mass on the M4 targets?

I'll end this post with a better question: Does it even matter?

The Cheese · Feb 28, 2009

ghanderson10 said:
I'll end this post with a better question: Does it even matter?

It matters based on what you want to use the rifle for. I mean, I can hardly hit a target at 300yds with a 3x acog so hitting something open sight at 300yds/m is seriously pushing it for me. For the one AR I have, I have it set for 100yds/m I know I can make shots ok to 200, but my skills are not as such that I would be even remotely tempted to take a shot at 300. But this is more to do with my lack of practice and serious lack of long distance range availability (which will hopefully be changing soon).

The difference in barrel length is somewhat negligible. You aren't really gaining a lot with a 16 over a 14.5" barrel. At 300yds you might see a bit of difference, but I doubt it would be more than an inch or two tops (assuming, like me, you can actually hit the target at that distance).

I guess the best thing to do is to zero your rifle and go to 300yds and see what happens. This kind of trial an error testing can be a lot of fun (if you get it right) or frustrating as heck (if you don't). If you have never shot to 300yds/m, but zero your rifle for it i think it would end up being a bit of a waste. besides you can always re-zero if need be

.

ghanderson10 · Mar 1, 2009

Mainly I'm zeroing for 300m because it's what I'm most comfortable with on an AR. As far as hitting stuff goes though, a 300m man-size target isn't terribly difficult to hit from the prone...but if you're talking about competition type stuff, then I second your opinion. The AR's pretty much the only thing I zero for 300... with an exception. Went shooting at Brown's today with my scoped AK that I zeroed for 300. Was hitting a 200m target pretty consistently, which surprised me, lol. Granted, the target was 8 inches wide, but I guess AKs aren't as bad as people would have you believe

Stomper · Oct 26, 2018

Barrel lengths and ballistics not withstanding, y'all aren't factoring in the differences in sight radius from carbine, mid-length, and rifle length gas systems in this discussion. The geometry of the sight-line above the bore-line is affected and therefore will affect the elevation setting of your battle-sight zero.

All things being equal using an A4 upper with carry-handle and an F-marked FSB to maintain the same height above bore-line, the angle of intersection (or deflection) of the sight-line and bore-line will be steeper with the carbine gas length and decreases the longer the sight radius gets with the mid, and rifle lengths.

11Charlie · Oct 26, 2018

Holly thread revival Batman!!

Stomper · Oct 26, 2018

SKrueger said:
Holly thread revival Batman!!

LOL.... what can I say, I was due.

Stomper · Oct 26, 2018

But what I said was PURE OBSERVATIONAL GENIUS!! :s0062:

Stomper · Oct 26, 2018

SKrueger said:
Holly thread revival Batman!!

9.5 years.... could be a new record... LMAO!! :s0166:

rcnpthfndr · Oct 26, 2018

no doubt, here read this, grouping and zeroing is towards the back appendix G IIRC.

https://fas.org/irp/doddir/army/tc3-22-9.pdf

this kind of makes me think why couldn't we have a members only cloud drive where we could have all this archived. if there are issues opening it let me know and I will post the pages on here. Now back to PD-100s

11Charlie · Oct 26, 2018

Stomper said:
Barrel lengths and ballistics not withstanding, y'all aren't factoring in the differences in sight radius from carbine, mid-length, and rifle length gas systems in this discussion. The geometry of the sight-line above the bore-line is affected and therefore will affect the elevation setting of your battle-sight zero.

All things being equal using an A4 upper with carry-handle and an F-marked FSB to maintain the same height above bore-line, the angle of intersection (or deflection) of the sight-line and bore-line will be steeper with the carbine gas length and decreases the longer the sight radius gets with the mid, and rifle lengths.

Hey brother you are spot on just thought it was funny it took you 9 1/2 years to come up with the answer!!! :s0121: