17hmr vs 223 trajectory

[paulham]

Hey, wondering if some one can help.

I've got the photon zeroed on my 17hmr with quick release weaver mounts, my 223 also has weaver bases, if I was to put the photon onto the 223, is there a way to know how far the zero would be out?

[V8 90]

Sure is - aim at a target at desired distance & hey presto POI clearly shows how far out it is

[paulham]

Before going out.
I would like to get near enough before I go out.

[V8 90]

Take the bolt from your rifle - put your rifle on a maintenance bench or a bean bag or whatever so it's held firm - point the rifle at a wall or fence or whatever you have at around 15m - pick out a knot or small mark & centralise the mark by looking down the barrel from the breech - now, without moving your rifle look through the scope & see where the dot is aiming - I did this with my .22lr & my Hmr 2 weeks ago, when I fired at my zeroing targets I was within 1"

[fizzbangwhallop]

Not really a way around it...... back to basics and bore-sight it as V8 says to get you on the paper...... I'd also set a spirit level across the turrets to level the rifle/'scope. The your first shots at 25m where you want to be around 1 to 1.5" low then out to 100m. Don't forget the number of clicks at 25 is 4 times the 100 click.

Count the clicks if you're intending to switch the Photon between the 2 rifles. But bear in mind that quality 'scopes will have repeatability on the clicks but I don't know if the Photon falls into that bracket.... you'll just have to suck it and see. You could try the usual..... fire a shot, x clicks right, shot, x clicks down, shot, x clicks left, shot, x clicks up, shot and with luck you'll have a square and the last shot on the first.

Simples.

(He said.)

Have fun.

Fizz

[paulham]

Cheers guys, ill have to do it the pratical way, I was hoping for a nice confusing mathematical way. Lol

Thanks
Paul

[paulham]

Was going to write this up last night when I got back but I fell asleep.

So I walked up to the abandoned pickup truck which is at the top of the field at the muckheap, it gives a nice table to put all my kit on, and I shoot from the roof down a hill to a target set up on the fence 89meters from my shooting position. The land steeply rolls up behind this so I know all is safe.



I swapped the photon from the 17HMR and onto the .223, I took 2 shots at the target and went down to check my shot placement. No marks at all, not good.
I took the target back with me and set it up at 40 meters (approximately, my range finder got stolen from my car, so I try to range find using my iPhone and a its GPS)



At 40meters the shot was an iPhone length high (thinking about it now, I had a tape measure in my bag, haha) so 11.5cm high.

Onto a quick zero chart , I worked out that 11.5cm high, at 40meters, on a 1/4" moa scope equals to 37 clicks down.

Then I went onto Ballistic AE iPhone app, set up the zero for 40 meters, then worked out how many clicks were required to zero at 89meters = 14 clicks down

Total 37 + 14 clicks down = 51

Then I did a test shot at 89m, 1.5" low, not bad for abit of maths, 7 clicks up and 8 clicks right and we were bang on .

I took the photon off the 223 and put it back on the HMR, reverted the clicks and took 3 shots, all as expected.
Put the day scope back on the 223, took 1 shot, bang on.

So I'm happy. At any time I can swap over the photon between my rifles and know where the shot will hit.