Thread: 7mm rem mag factory ammo cds data

After some help with the leupold cds. I've just purchased a tikka t3x elite in 7mm rem mag with a dpt suppressor on it. I've got a vx3 to go on top. I'm going to be running the Hornaday proformance hunter factory ammo (162 grn i think it is ) . Is the load data off the box accurate enough for ordering a new dail cap ? The scope currently has a custom cap for a 223 and my factory one is about 9 hrs away from me.

No

The superformance 154ssts actually matched the box in my tikka which is amazing but almost never happens that way. Id get a custom moa dial with a zero stop made instead

You should really chrono it. Measure the height over the bore of the scope. Hornady provide banded BC's for ELD-M and ELD-X projectiles - find those. Work out the average air pressure, temp and humidity for the areas you hunt in. Punch all that data into an app like strelok. It'll give you a drop chart.

Give that drop chart to NZ asia. It'll be much more accurate than what's written on the side of the box. Better still, head out and confirm it at long range first.

+1 for above, & myself would not bother with a custom turret - just use moa & work with your drop charts or app. You're bound to want to change projectile or load at some point then your custom dial is redundant

Unless you're a real rich bloke, you'll be looking to do an abbreviated verification for setup.
Yes, get a new custom dial for your 7RM. It won't differ much between brands and you can check and work out whether you need an extra click or not if you change in future.

My suggestion:

Use a laser rangefinder. Buy, borrow or whatever.
Pay for Strelok Pro and get advice how to use it.

Fire 2 x 3 shot group at 100m or 200m whichever you'll use, to get it well zeroed. Also check you're getting < 2MOA groups otherwise you'll need to start again after solving accuracy problems. With a Tikka/Leupold combination it would only be inadequate sandbag/ rest equipment.
Don't bother with a chronograph. You will work out a velocity from drop of actual shots on target.

Shoot a 3 shot group at 300m or 400m approx. with the sights still set on zero and carefully range findered distance. Use enough paper. Your shots will drop 600 to 1000mm from the aim point, so you will need a tall piece of corflute and a full fresh newspaper or spare wallpaper / butchers paper or something behind. The important thing is not to lose any shots off the paper. Don't take any shortcuts and try to adjust after only one or two shots. Let them fall where they may and analyse after you've fired 3. The idea is to get an actual real world drop figure in cm or inches. Plus you get an idea of your system's grouping capability in ideal conditions. This is your primary backstop for confidence.

Then start with an estimated velocity (use the packet value adjusted by 25 fps per inch of barrel assuming the packet figures are for a 24") and put that into Strelok. Adjust the velocity up or down so the predicted point of impact matches your observed one. It can be hard to make yourself do this on a noisy range when you're in a hurry but you need to.

Next, use Strelok to calculate how far you need to adjust up in clicks or MOA at your test range. Dial up what it says and fire 3 more shots. These should be centered fairly well around your aim point. Realistically, you can't sight in better than the size of your group, which will be quite large at 400m. Again, don't take any shortcuts or fire extra shots. You need to work on clean paper and see where every shot falls. A small adjustment to the velocity might be needed, but look at both 400m groups and think carefully whether it's warranted.

Now you have a BC (from the Strelok library) and a muzzle velocity which you can send to Leupold for your CDS. If all goes well you could do this with only 12 shots. Don't expect perfection.

When the CDS arrives, you can check and set it at your zero range with 2x3 shot groups and then dial for another 3 shots at the long test range like 300 or 400m, which will take another 9 shots in total. It won't be spot on for every group and you might need to allow an extra click or few at some longer ranges.

Always use plenty of paper.

Altitude and air pressure can make small differences to trajectory out past 300m but realistically unless you're reloading and shooting 50 rounds to set up your system, you won't be able to allow for this.

There is a thread here with altitude and ballistics.
Roughly:
100m ASL 1000 hPa
500m ASL 950 hPA
1500m ASL 850 hPa
put those into strelok and see what you get.

ok heres a left field thought for you....go into $2 shop and buy bottle of nail varnish......use your 223 dial...and mark it with the varnish for your 400/500/600/700 marks......you shouldnt need to dial closer than that.... not sure how many 100 yards you will get in full turn of dial..... but not hell of a hard to do it without all the fluffing around with new dial.... but Im a cheap bugga.

Originally Posted by Micky Duck

ok heres a left field thought for you....go into $2 shop and buy bottle of nail varnish......use your 223 dial...and mark it with the varnish for your 400/500/600/700 marks......you shouldnt need to dial closer than that.... not sure how many 100 yards you will get in full turn of dial..... but not hell of a hard to do it without all the fluffing around with new dial.... but Im a cheap bugga.

Greetings Micky,
It might be the curmudgeon in me but I can't help thinking if you tried to explain the good info above to a good 1980's hunter their eyes would have glazed over quick smart.
Regards Grandpamac.

Cheers for all info, some really helpful point there.much appreciated.