Help me with scope subtends on my 308 scar and my ffp scope please.

[anymanusa]

Okay, back ground info; I have 8 milliradians up, and 8 down, from my crosshairs. Right now I have it set to where I move vertical up(point the tip of my gun down) my crosshairs to +5.5mil and I will be sighted in for 100yard shooting.

If I move up to only 5mil, I'll be sighted in for 200yard shooting. If I move up to 4mil, I'm good at 300yards, and if I just barely move up to 0.5mil, I'm good for 600yard shooting.

So this puts my crosshairs right around a little more than 600yards. What range can I expect my bottom 8mil subtends (pointing the barrel of the gun up) to be good for? I realize I'm leaving a lot out, so let me help by saying the ammo: malaysian surplus 146gr bt 7.62x51 from '82. I don't have velocity numbers yet.

Any help understanding this would be appreciated. This is difficult to predict, as not a single calculator seems to provide similar results.

If any of that was hard to understand, basically my rifle/scope are sighted in at 600yards and I have to point my rifle down to shoot at 100, 200, 300,400, or 500 yards. I wanna know how long in theory the bottom half of my scope subtends are good out to.

Thanks .

 

[Varminterror]

8mil below 600yrd zero, assuming .375 BC and 2750fps, and assuming you have a large enough target to make contact with surplus ball junk which falls transonic around 900-950yrds would be a ~1025yrd hold over, and keeping in mind, your danger space is incredibly narrow, as this chubby little bullet is dropping over an inch per yard.

I’m a knob turner, never been a fan of using the top half of my reticle for anything more than ranging. I know there are really experienced and really popular guys like Hodnett who regularly teach it, and if a guy doesn’t have any form of Christmas Tree, it can be useful, but it completely ignores the advantageous ability to utilize your MPBR... You’re stating a mil and a half between your 100 and 300 hold because you’re playing with your 600 zero, whereas with a 225yrd zero, it’s only 0.5 difference in hold... with a 225yrd zero, I can ignore any trajectory and hold on target to 250, and be working within 1mil to 250, and then that bottom 8mil stadia is still 850yrds... So I can hold center 0-250, hold over to 850, and then have to dial anything further. In your system, you’re holding over/under from 0-1025yrds. If a 1000yrd shot is as likely as a 200yrd shot, your system has merit. In my experience, that’s not realistic, so I zero to ~200-250, hold when I have to, and dial most of the time. You’re not making a 1000yrd shot with a 146grn surplus 308win without ample set up time anyway.

 

[Klint Beastwood]

[QUOTE="anymanusa, post: 10757050, member: 51227"

Any help understanding this would be appreciated. This is difficult to predict, as not a single calculator seems to provide similar results.


Thanks .[/QUOTE]

You have a lot to figure out before those calculators work for you. A mildot isn’t a BDC really. Varminterror hit the nail on the head as usual.
What scope are you running?

 

[anymanusa]

Thanks for the replies. It's not that I'm trying to make a 1000 yard shot at all. I'm really just trying to understand how I want to shot, turning knobs, or using the reticle. I've just now started shooting out to 600 and I'm gonna make a few long range targets at some property of the fil's, but those will likely have some inclination or declination to them. I'm trying to get to the point where I understand what it takes to hit from one distance to the next, and then I'll add a little inclination or declination into the mix and try to further my understanding. A lot about this is very confusing to me. I've always been good at math and calculations, but there are alot of things about milliradians and shooting that I just don't understand right now.

For instance, if I zero at 400yards, and want to make a 600 yard shot, that 200 yards of distance is much different than the 200 yards fdom 0 yards out to 200 yards. I'm just trying to wrap my brain around this. I want to eventually build the knowledge base to walk around my fil's 2000 acres and make a shot, wherever I can, when it's whitetail season. Sometimes that might be 500 yards away in a open field shooting downward, other times not.

 

[Walkalong]

A mildot isn’t a BDC

Yep. Not that some people don't do it. The Mil-Dot reticle is for ranging, then you dial in the distance.

 

[Varminterror]

Even if you want to use the reticle, you'd get out to 850yrds without touching your knob, and you'll make your short range shooting life a lot easier by using an MBPR zero at 200-225yrds, not a 600yrd zero.

There's really no magic or mystery between the distance dropped from 400 to 600yrds vs. the drop between 0 to 200yrds - it's all gravity. 32.17 ft/sec/sec... Our barrel is always pointing slightly above the centerline of the scope, much like shooting a basketball upwards above the rim, planning to hit the backboard in the box to bank into the net. Don’t over think this - 500 & 600yrds aren’t long range yet, it’s “mid-range,” and it’s classed that for a reason, you have a lot less demand of skills and knowledge at 600 than at 1,000, so don’t get too caught up in the math. Shoot the rounds, record the corrections, and enjoy life. Any laser rangefinder on the market these days has angle compensated range calculations built in, so there’s really no reason a guy has to break out trig tables. Compensated range = line of sight range x cosine (shooting angle). You can buy a cosine indicator to mount on your optic or rail, so you don’t even have to calculate or look up cosine... or again - just use your laser rangefinder.

 

[Varminterror]

Yep. Not that some people don't do it. The Mil-Dot reticle is for ranging, then you dial in the distance.

Guilty. I NORMALLY dial, but I do often make my hold over corrections at mid-range with the dots. #lazydays #stillconnect

 

[anymanusa]

Even if you want to use the reticle, you'd get out to 850yrds without touching your knob, and you'll make your short range shooting life a lot easier by using an MBPR zero at 200-225yrds, not a 600yrd zero.

There's really no magic or mystery between the distance dropped from 400 to 600yrds vs. the drop between 0 to 200yrds - it's all gravity. 32.17 ft/sec/sec... Our barrel is always pointing slightly above the centerline of the scope, much like shooting a basketball upwards above the rim, planning to hit the backboard in the box to bank into the net. Don’t over think this - 500 & 600yrds aren’t long range yet, it’s “mid-range,” and it’s classed that for a reason, you have a lot less demand of skills and knowledge at 600 than at 1,000, so don’t get too caught up in the math. Shoot the rounds, record the corrections, and enjoy life. Any laser rangefinder on the market these days has angle compensated range calculations built in, so there’s really no reason a guy has to break out trig tables. Compensated range = line of sight range x cosine (shooting angle). You can buy a cosine indicator to mount on your optic or rail, so you don’t even have to calculate or look up cosine... or again - just use your laser rangefinder.

Yes there is, there is a big difference because you get way more drop over the distance that your projectile is going slower than where it is going faster. That's just one of the things warping my brain.

 

[Varminterror]

Ain’t magic - it’s just physics. Don’t over-think it. The lateral velocity isn’t something you need to know - you’re short enough range you’ll be super sonic, so all you need is a way to read range and sufficient DOPE (meaning: put the calculator away and go shoot). Your bullet is traveling slower horizontally, AND it has had more time under gravitational acceleration - if you’ve ever shot a basketball, you know projectiles fall faster at the back end of their travel than they do at the front - you’re over thinking this.

It takes me somewhere around 20 shots to go from “brand new rifle,” to holding a card with “good preliminary dope” out to 800yrds... about two hours of my life... one run through Advanced Ballistics App... 500-600 isn’t asking much, just go shoot.

 

[Klint Beastwood]

Thanks for the replies. It's not that I'm trying to make a 1000 yard shot at all. I'm really just trying to understand how I want to shot, turning knobs, or using the reticle. I've just now started shooting out to 600 and I'm gonna make a few long range targets at some property of the fil's, but those will likely have some inclination or declination to them. I'm trying to get to the point where I understand what it takes to hit from one distance to the next, and then I'll add a little inclination or declination into the mix and try to further my understanding. A lot about this is very confusing to me. I've always been good at math and calculations, but there are alot of things about milliradians and shooting that I just don't understand right now.

For instance, if I zero at 400yards, and want to make a 600 yard shot, that 200 yards of distance is much different than the 200 yards fdom 0 yards out to 200 yards. I'm just trying to wrap my brain around this. I want to eventually build the knowledge base to walk around my fil's 2000 acres and make a shot, wherever I can, when it's whitetail season. Sometimes that might be 500 yards away in a open field shooting downward, other times not.

Some of this might help with your dope. Print them, save them, use them, through them away, its free so if it helps a little then great
If it belongs in a data book somewhere, I probably have it..

 

[anymanusa]

So if I shoot at 3mil above crosshairs at 300yards, do I just screw the turret down 3mil to make the zero at crosshairs 300yards?

That sounds right to me, but it wouldn't be the first time something sounded right but wasn't right.

 

[Varminterror]

Yes. Run your trajectory with your actual MV to get your ideal MPBR zero. It won’t be 300yrds.

 

[ar-newbie]

I zeroed for 100 yards, then ran my load data through a ballistic calculator, and made a label for my flip up scope cover, which tells you how many clicks of elevation to dial for a specific range, both under 100 to 25, and over 100 to 600 yards (practical limits of my load and caliber)

 

[z7]

What scope? Is it mil reticle and a mil turret?

If so dialing is pretty quick and easy, I would consider 200-400yd zero and dial anything over 800yds

When I used the Bottom of my scope I find that the image is a little off and it strains my eye, I am using a vortex razor gen ii so it’s not a cheap scope, just focusing on that bottom of the scope isn’t easy for me

Hornady and others offer good online free ballistic software, jbm ballistics has a lot of features where you can adjust the variables to see how various zero distances impact holdover/under

 

[anymanusa]

Vortex viper pst ffp 6-24 gen I right now at the range, but I'm trying to decide on a better suited optic for my purposes.

Mil turrets and mil reticle.

 

[Chuck R.]

You might be a candidate for something like Strelok Pro, a ballistic app for your phone.

The programmer has included a a lot of reticles in it, so there's a good chance you can enter your data, pick your reticle and then get your come-ups and an image of where to hold using your reticle. It's about an $11.00 investment on Google Play.

I zero for 200, and dial in most of the time for greater distances. About the only time I don't is when we're shooting at multiple targets at diffrent ranges "on the clock".

 

[Driftertank]

I use Strelok free edition...not sure what extra features Pro comes with, but even free can get me hitting steel out to a half mile.

 

[Chuck R.]

I use Strelok free edition...not sure what extra features Pro comes with, but even free can get me hitting steel out to a half mile.

Biggest benefit I see is Pro links directly to my Kestrel for weather data. It also has more reticles and preloaded bullet profiles. Also it allows for inputting multiple MVs with temps to sort out powder temp sensitivity.

It really does help with 1st round hits.

 

[IndianaBoy]

Vortex viper pst ffp 6-24 gen I right now at the range, but I'm trying to decide on a better suited optic for my purposes.

Mil turrets and mil reticle.

Which mil reticle? That scope is available with the EBR-2C and the EBR-1.


Strelok is the easiest path to good firing solutions that I have found. You really need to be able to chronograph your ammo, although you can accomplish the same thing by carefully evaluating your real trajectory through live fire.


It is a bit unusual to zero in the manner that you are, but not unworkable.

I think you would be ahead to zero you main crosshairs at 200 yards, understand your over/under for distances from 0-200, and use the bottom portion of your reticle out to 800 or so.

 

[IndianaBoy]

A mil reticle can absolutely be used as references for holding over. You just need to know your dope, and how many mils you need to hold for a given distance and a given wind value.

Horus type reticles, or the Vortex EBR-2C are popular for this reason, to give precise MIL holdovers without constantly dialing.

 

[Driftertank]

I use a 200yd zero on most of my rifles. I usually hold over (EBR-1 MOA on my .308 and 7mm; i think in inches). Like i said, Strelok gets me on out to about a half-mile if i can read the wind.

 

[Varminterror]

The apps are cheap medicine... they might cost more than Angry Birds, relatively, but I know two truths about Strelok Pro and Advanced Ballistics Mobile:

1) I rarely if ever spend less in ammo cost at every range session, so they really aren’t prohibitively expensive.

2) Either will save you more ammo than they cost, quickly. First or second round hits cost less than 4th or 5th round hits.

 

[anymanusa]

Which mil reticle? That scope is available with the EBR-2C and the EBR-1.


Strelok is the easiest path to good firing solutions that I have found. You really need to be able to chronograph your ammo, although you can accomplish the same thing by carefully evaluating your real trajectory through live fire.


It is a bit unusual to zero in the manner that you are, but not unworkable.

I think you would be ahead to zero you main crosshairs at 200 yards, understand your over/under for distances from 0-200, and use the bottom portion of your reticle out to 800 or so.

It's the gen 1 scope, only 1 reticle in mil fashion. I can go back and re-zero any time I want, what I'm trying to do now is understand all of this, not achieve a particular "zeroing" or anything.

 

[Klint Beastwood]

Really there should just be a 100y zero. Less environmental factors brought into the zero itself.
I understand a Pbr but that’s not what we are talking about here.
Next, you need to establish what your drop is...preferably in your density altitude...take notes.