-2.4 at the Muzzle

[TwitchInForest]

Hey Horde - question for you: I was looking at the ballistics for the Hornady Black 123 gr ELD Match round that I have been shooting, and I don't understand something that is listed in the trajectory column. I don't understand why the trajectory is listed as -2.4 at the muzzle. The chart from the Hornady site is here:

Grendel Ballistics.PNG

Can anyone clarify?

Thanks!

Twitch

[A5BLASTER]

What it is telling you is with a 200 yard zero your muzzle is 2.4 inches below your point of impact of the 200 yard zero.

If you change too a 100 yard zero, your muzzle would be bout half to 3/4 inch below you point of aim for the 100 yard zero.

If you zero at dead on at 25 yards you will be bout a inch high at 100.

Hope this helps sir.

[Drillboss]

Hey Horde - question for you: I was looking at the ballistics for the Hornady Black 123 gr ELD Match round that I have been shooting, and I don't understand something that is listed in the trajectory column. I don't understand why the trajectory is listed as -2.4 at the muzzle. The chart from the Hornady site is here:

[ATTACH=CONFIG]13297[/ATTACH]

Can anyone clarify?

Thanks!

Twitch

Their test barrel was set up with the reticle (center of the scope bore) 2.4" above the center of the barrel bore. If their scope were 1.5" above the barrel, the trajectory would have been -1.5" at the muzzle.

[NightFisher]

Their test barrel was set up with the reticle (center of the scope bore) 2.4" above the center of the barrel bore. If their scope were 1.5" above the barrel, the trajectory would have been -1.5" at the muzzle.

+1

[1Shot]

+1

Yep, and people don't understand that the muzzle is actually pointing up with the scope pointing at the zero point.

[Klem]

Hey Horde - question for you: I was looking at the ballistics for the Hornady Black 123 gr ELD Match round that I have been shooting, and I don't understand something that is listed in the trajectory column. I don't understand why the trajectory is listed as -2.4 at the muzzle. The chart from the Hornady site is here:

[ATTACH=CONFIG]13297[/ATTACH]

Can anyone clarify?

Thanks!

Twitch

+2

The bore height of an AR is about 2.5" compared to the bore height of a typical hunting bolt gun, at 1.6". When the bullet comes out of the muzzle they are predicting it will be 2.4" below the scope axis. The person who compiled those ballistics presumed those interested in it would be using an AR. Ballistics software like the apps we use on our phone or in our Kestrels will have a user-adjustable scope height to cater for the exact bore height of the rifle you are using.

[Wargrendeleagle]

Does it change much with an AR? I guess if like to find out exactly what mine is to put in strelok. So I see what the mount manufacturer says the height is and add how much for the center of the bore? According to Aero it's 1.5" from base to center of rings

[Klem]

The distance from the middle of the bore (bore axis) to the top of the rail on an AR is 1". That makes your height from bore axis to scope axis on your gun = 2.5"

You can get different heights of mounts for an AR but the standard is pretty much 2.5"

[Wargrendeleagle]

The distance from the middle of the bore (bore axis) to the top of the rail on an AR is 1". That makes your height from bore axis to scope axis on your gun = 2.5"

You can get different heights of mounts for an AR but the standard is pretty much 2.5"

Great. I guess I could have googled it vs hijacking OPs thread but it's good info. Thanks!

[TwitchInForest]

You know those moments when you ask yourself, "why didn't I think of that?" As soon as I read your posts it made pefect sense... Sometimes I'm not the sharpest tack in the pile.

I appreciate the clarification.

[Klem]

Yep, and people don't understand that the muzzle is actually pointing up with the scope pointing at the zero point.

With respect, I don't think you mean exactly what your words are saying.

On a scope mount with no forward cant the scope and bore should be exactly parallel. More precisely the scope axis and the bore axis should be exactly parallel. The reticle in the scope is then moved by dialing the adjustments. The reticle goes up/down/left right inside the fixed, parallel scope to bring the reticle to coincide with where the bullet is landing at a particular zero range.

If the scope sits on a canted mount, like a 20MOA mount then sure, the scope is angled relative to the bore axis, but the same principle above still applies.

I'm pretty sure this is what you meant to say so apologies and just ignore me if it is.

[Popeye212]

Here is a good explanation and video https://www.youtube.com/watch?v=VqOqZBRZsj8

[TwitchInForest]

Thanks everyone, those answers helped a lot. My AR is zeroed and shoots about 2" high at 100. This past weekend I was shooting with a friend at a range that only had a max of 25 yards. I was consistently seeing my shots land about 2" low with the reticle centered on the bull. That made sense to me, well, I think it did at least, because at 25 yards the round hasn't had much time to climb considering it will be at zero at 200 yards.

My buddy told me that the rifle couldn't be zeroed correctly because the POI wouldn't be below to point of aim at that distance - he felt it should be high, not low.

Quite frankly, his argument confused me and I'm not so sure who is right. I do know that if I shoot it at 100 I am right where Hornady claims the round will be - approximately 2" high.

What do you guys think????

Thanks!

Twitch

[LRRPF52]

Thanks everyone, those answers helped a lot. My AR is zeroed and shoots about 2" high at 100. This past weekend I was shooting with a friend at a range that only had a max of 25 yards. I was consistently seeing my shots land about 2" low with the reticle centered on the bull. That made sense to me, well, I think it did at least, because at 25 yards the round hasn't had much time to climb considering it will be at zero at 200 yards.

My buddy told me that the rifle couldn't be zeroed correctly because the POI wouldn't be below to point of aim at that distance - he felt it should be high, not low.

Quite frankly, his argument confused me and I'm not so sure who is right. I do know that if I shoot it at 100 I am right where Hornady claims the round will be - approximately 2" high.

What do you guys think????

Thanks!

Twitch

The chart you posted in the OP answers your own question. Look at where the trajectory is at 100yds with a 200yd zero:

[TwitchInForest]

Thanks, LRRP. I was thinking the same thing. At 25 yards I expected the rounds to hit low, approximately the height of the scope centerline above the bore centerline, but my buddy argued with me seven ways from Sunday how the rifle wasn't zeroed properly. I attempted to explain that I would be approximately 2" high at 100, and zero at 200, but to no avail. Shooting with a scope on a AR is new to me, so I struggle to make an intelligent argument as I am just learning myself. He, on the other hand, has years of shooting experience and is a pretty damn good shot, but I thought he was wrong in this case.