The trouble with holdovers

I was testing the trajectory of my 17HMR (17gr VMax).

I sighted it in for 50m then shot at 197m with no hold over.
This is the "tall target test".
It is true. It shows the actual trajectory in cm.
There is no distortion even if your clicks aren't exact or if your reticle or magnification are not to spec.
The result was 5 shots striking 24cm below the aim point. The group was about 4cm tall, 15cm wide and 12 cm left of midline. Wind was about 2m/s from 2 O'clock. But I'm ignoring windage because my horizontal zero was spot on at 25 and 50m.

OK 24cm at close enough to 200m is 1.2 Mils
So hold over 1.2 mil dots ...

Attachment 247271

Blurg !
4 shots are averaging 8cm lower than planned.
The problem was that I had shot on 12x but the reticle is second focal plane and is calibrated at 10x.
Those 1.2 Mil dots should be 1.2 x 20 = 24cm.
But increasing the magnification to 12x expands the target underrneath the reticle by 1.2x.
So what should have been 24cm is 24/1.2 = 20cm.
Perhaps I was holding a bit less than I should have, distracted by the half mil hashes between the dots ?
So the group was OK but not centred well enough to hit a hare at that distance.

Then there is the shot near the top of the target, pretty much 1 Mil above the other 4. Another miss !
I'm guessing I held over 2.2 mil dot instead of 1.2 mil dot. Easy to do. Looks like I did it.

So, I'm thinking it would need quite a lot of drilling and visual training to hold over every time using mil dots and its not a reliable proposition for me with a second focal plane scope.

Or just use it at 10x where it's calibrated for, bit yes u right it does take practice to get to know your gear. Dedicated marksman in army was on range 3 -5 x a week

Dial for your shots please

Save yourself all the anxt

Most of my scopes are 2nd focal, with practice it's not hard to remember the changes in angle magnification makes

Rabbit shooting with a17 hmr, you have from the top of the head to the chest to sort your drop, I sight mine at 100 metres

Quote:

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Originally Posted by 7mmsaum

Dial for your shots please

Save yourself all the anxt

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Some scopes don't (even though they are supposed to be able to be dialled)... Knowing your gear and what it can do is more the key, along with good dope notes and doing the same routine every time (setting to the mag that the SFP is calibrated on - some SFP scopes don't actually have this marked on the mag ring and don't tell you in the manual which is a pain in the arse).

You can also just figure out what the subtensions are between dots when the scope is set to 12x, if you’re using a chart, adjust the chart values to suit.
Finding full magnification is usually easier than finding magnification setting two settings below full. Full can be found by feel.

I run a 17HMR a lot. I am sighted in ( zero ) at 100mtrs . This range covers 80% or the shots I need to take from 40 - 130 mtrs with basically point and shoot .
Over the 130mtr mark to 190mtrs plus I just hold over. I have put so many rounds through the rifle I know instinctively how much hold over to use.
It doesn't work 100% of the time but generally I am on the money.
I can't be arsed with dial up as were I shoot has a lot of rabbits and it's too time consuming to be messing around with turrets.
It may not be very hi tech but Kentucky windage works for me in my situation. instinctive, fast and effective for rabbits.

I suspect you also developed a good eye for estimating range as well if your using a mildot style reticle

Greetings,
What was the actual velocity of the ammo fired and was it consistent?
GPM.

Thanks GPM, no I didnt chrony it.
I’ll get baCk to you with an est tried mv based on the true drop from the 200m tall target.

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Originally Posted by Marty Henry

I suspect you also developed a good eye for estimating range as well if your using a mildot style reticle

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You are correct, 9 years of shooting central Otago rabbits with talleys into the tens of thousands has turned range estimates into second nature. Also shooting the same farms has given me landmarks that I have shot from before or have a good estimation of the drop at that distance. My scope is just a cheap Nikko Stirling but it has hash marks on the reptile. What those marks mean i have no fucken idea, however I know just over 3 marks down gets me rabbit accurate at 190mtrs. It's hardly scientific but it is effective for my style of shooting.

Quote:

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Originally Posted by viper

You are correct, 9 years of shooting central Otago rabbits with talleys into the tens of thousands has turned range estimates into second nature. Also shooting the same farms has given me landmarks that I have shot from before or have a good estimation of the drop at that distance. My scope is just a cheap Nikko Stirling but it has hash marks on the reptile. What those marks mean i have no fucken idea, however I know just over 3 marks down gets me rabbit accurate at 190mtrs. It's hardly scientific but it is effective for my style of shooting.

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I am also unsure of hash marks on the reptile, but I agree with your methods. With my .22 I have simply checked drop in 10yd increments after 50yds. No calculator or MV needed, just real world data from simple real world testing. At that point the maths is redundant.

Quote:

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Originally Posted by Bagheera

I was testing the trajectory of my 17HMR (17gr VMax).


.


The problem was that I had shot on 12x but the reticle is second focal plane and is calibrated at 10x.


Perhaps I was holding a bit less than I should have, distracted by the half mil hashes between the dots ?

Another miss !
I'm guessing I held over 2.2 mil dot instead of 1.2 mil dot. Easy to do. Looks like I did it.

So, I'm thinking it would need quite a lot of drilling and visual training to hold over every time using mil dots and its not a reliable proposition for me with a second focal plane scope.

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HMMMMMMMM you have stated here you already KNOW WHAT PROBLEM/ISSUE IS ...so where is the problem again LOL.

this is one of the advantages of a fixed power scope...nothing changes,its the same every time.
it matters not if you do 10x or 12x if you do it every time and work out your marks etc beforehand..consistancy is and has always been the name of the game. repeatable consistancy is the be all and end all of hitting what you aiming at..always has been and always will be.

a commercial fence batten is very consistant in length..... the distance plantation trees or vines are planted apart is also consistant...once you learn what they look like through scope at different given distances your half way there.

Attachment 247304

Not perfect and will vary a little for temperature ( air density ) altitude and rifles but this will give you a pretty good starting point and all you need.

Just hold over at 10x where the reticle calibrated.
Or buy an FFP scope.

Being old, I've always relied on the sight picture. Just got used to it with practice. Quite happy shooting offhand out to around 100m on a rabbit or hare.

The best point blank zero for 17hmr is 100m. I use a Nikon BDC 2-7x32, and Stelok. Best shot so far is my 14 year old knocking a bunny in the head at 180m (I couldn't even see the damn thing). We do use a rangefinder.