Thread: Hunting Scope Magnification

Originally Posted by Shearer

So the bullet is rising to line of sight all the way to 100m?

Yes. Most centre fire rifles shoot flat enough that with a 100m zero the line of sight through the optic has not yet cut below the trajectory of the projectile (if it will cut below). With a 200m zero this first point of crossover comes sooner therefor your line of sight is closer to the line of trajectory at those closer bush ranges.

visualise if you will that red line connecting at hundy and you will se it HAS to climb from muzzle to connect at hundy.... make it slightly high at hundy and it will cross before and somewhere after....so on average be closer to where you want it to be...the theory being my projectile will not be outside of the magic/theoritical 8'' vital area with a centre of vitals aim untill.....250 yards....and the above is a fat,heavy for calibre round nose......

Moved from 2-7 to 3.5-10 due to aging eyes struggling a bit. If I have the money at some point I'd swap it for a VX5 or 6 with 2-10 or 2-12 but happy enough with what I've got now.

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First off 300m is a long shot for me.

1.5-8 x 32 on 308
1-4 x 20 on 30-30
4 x 32 or red dot on .22rf
2-7 x 32 on .22WMR
3-9 x 40 on only CF bolt action tomato stick

I know high mag has its place but my eyes are not to bad yet, and until then I will resist the trend.
Firmly believe its about bolting a scope to a gun, not a gun to a scope. Those big 50+ objective telescopes leave me cold.

Originally Posted by Micky Duck

fixed 3x fixed 4x or a 3x9 suits me down to the ground...I dont shoot past 300 yards more than once in a blue moon...and a red hind is still easily doable with fixed 3x at that range...for sure its a centre shoulder aim but thats where I normally shoot for any way. the smaller size of the wee fixed powers is a huge mind thing too...less to cart around,less to get hooked up, end of scope closer to rings so less chance of knocking out of whack/zero....easier to keep dryish on a wet day.

Hence why I used the 2.75x for 30+ years, WIDE field of view, seemed to not shake so much etc. ( but hoo-boy, did that thar seem to be shrink after viewing through the 8x binos!)

Originally Posted by stagstalker

Yes. Most centre fire rifles shoot flat enough that with a 100m zero the line of sight through the optic has not yet cut below the trajectory of the projectile (if it will cut below). With a 200m zero this first point of crossover comes sooner therefor your line of sight is closer to the line of trajectory at those closer bush ranges.

Ok. So the graph @Micky Duck has put up shows (a 30-06 maybe?) cutting the line of sight at about 25m? when sighted in at 200m. Where do you think it will cut the line of sight when sighted in at 100m?

Originally Posted by Micky Duck

visualise if you will that red line connecting at hundy and you will se it HAS to climb from muzzle to connect at hundy.... make it slightly high at hundy and it will cross before and somewhere after....so on average be closer to where you want it to be...the theory being my projectile will not be outside of the magic/theoritical 8'' vital area with a centre of vitals aim untill.....250 yards....and the above is a fat,heavy for calibre round nose......

Ok, being honest, this shit confuses me at times, so, going off that chart, would I assume a 25m zero sight in crosses back over at 200.
So anything between 25-100 I could expect up to a 3inch high hit, where as past 100 I can expect the opp ?

I have a 3-9x40 on my 30-30, if I don’t dial it down to 3 or 4 I lose sight when I fire as she kicks like a mule.
Should I just be keeping it down to 3x, sight it in at 25 yards, as most my goats have been around 60-150 yard range ?

Originally Posted by Shearer

Ok. So the graph @Micky Duck has put up shows (a 30-06 maybe?) cutting the line of sight at about 25m? when sighted in at 200m. Where do you think it will cut the line of sight when sighted in at 100m?

At 100m

Originally Posted by stagstalker

At 100m

Sorry. I meant the first time. Not at it's zero.

Originally Posted by Shearer

Sorry. I meant the first time. Not at it's zero.

Yup, at 100m

Originally Posted by Shearer

Ok. So the graph @Micky Duck has put up shows (a 30-06 maybe?) cutting the line of sight at about 25m? when sighted in at 200m. Where do you think it will cut the line of sight when sighted in at 100m?

Just move the line of sight (black line) up to intersect with 100 and there's your answer

A ballistic calculator can help clearly show these cross over points and how high/low the trajectory is in relation to the line of sight at each distance etc for specific rifle setups.

Ok. Still not convinced a typical bush rifle (say a 308win shooting a 150gn bullet at 2700fps) or any rifle/bullet combination for that matter, can make the bullet leave the barrel and only rise 1.5"(about the mounting height of your average scope) to get to 100m, and not cross the line of sight well before that). I was hoping a ballistics expert would enter the thread with another graph. I would be happy to be proved wrong.

@Shearer I put you slightly wrong. The example photos below are a rough 308 shooting a 150gr soft point at 2800fps. First photo is a 100 zero and shows the point at which trajectory meets LOS is about 70. You will see however that it doesn't really cross over and they stay together to 100 until the trajectory falls away again below LOS.

Second photo is at 200 zero and shows a very clear cross over for a period of time.

Hopefully that makes it clear enough. Also note that this is yards not metres, just a very simple ballistic app I have on my phone for mucking around with numbers.