Drop chart for 280AI

[MITCHMO]

Hi all, I have doing some shooting with my new 280 AI using federal factory 155 terminal ascent that seem to shoot at about 3000fps. I probably need to run a few more through to get an average but that’s what I have so far. I seem to not be matching the predictions for drop very well. I was wondering if anyone had any thoughts on how to gain a little more confidence in understanding what’s causing the difference. I’d really like a good match so I can easily make the shift when I go from 500’ elevation to 8000+.

The orange line is what I should have at home with the standard charts. The black is what I shot. The blue is the shift to account for the change of altitude if I fit a curve to my actual results. I’m a total novice so I’m looking to learn.

 

[MITCHMO]

I set up a 1/2” thick aluminum plate at 625 and shot one time with two different loads. The shot on the right with some bullet jacket in the hole is the 155 terminal ascent. The shot on the left was a 162ELDX.

 

[VikingsGuy]

To offer any thoughts we would need to see the "actual" shot data - the number of shots at each distance, the specific distances, the "scatter"/variance of the data. If you are just doing 2 or 3 shots at each distance you probably are inside of the statistical range of random variation.

Also from 0-400y your actual and theoretical are a very close match so you are good for 98% of good hunting shots.

 

[MITCHMO]

To offer any thoughts we would need to see the "actual" shot data - the number of shots at each distance, the specific distances, the "scatter"/variance of the data. If you are just doing 2 or 3 shots at each distance you probably are inside of the statistical range of random variation.

Also from 0-400y your actual and theoretical are a very close match so you are good for 98% of good hunting shots.

Yea there was only a couple shots at each distance. So maybe it’s back to the range. I’m running low on ammo so was trying to conserve before heading west. I’ve got 6 more boxes coming but they are way behind on shipping.

 

[VikingsGuy]

Cool exercise and your thinking is along the right lines, but to do this you need fairly tight precision with that rifle/ammo/shooter combination (consistently sub 1moa) and numbers of shots at each and every distance in the 7-15 range to start to make meaningful distinctions at the level of precision you appear to be looking for. Seems like it is not worth the time or cost - just keep your shots under 500y and enjoy.

 

[Deleted member 28227]

As much as I absolutely love a good graph, I've never needed to take a shot on a elk over 250. 4 were under 150.

 

[brymoore]

I’ve shot elk from 75 yards to 600 yards with plenty in between with my 280ao. My Shooter app has always doped correctly for me.

 

[MITCHMO]

I’ve shot elk from 75 yards to 600 yards with plenty in between with my 280ao. My Shooter app has always doped correctly for me.

What bullets you shooting? My Hornady app seems good until 500 then it goes crazy. Told me over 17moa drop and it was really 10.5.

 

[MITCHMO]

As much as I absolutely love a good graph, I've never needed to take a shot on a elk over 250. 4 were under 150.

I just like shooting long distances. Seems like every critter I shoot is under 50 yards. Nothing wrong with wanting to figure it out.

 

[Deleted member 28227]

I just like shooting long distances. Seems like every critter I shoot is under 50 yards. Nothing wrong with wanting to figure it out.

Oh absolutely the chart on my rifle goes to 700 lol

 

[brymoore]

What bullets you shooting? My Hornady app seems good until 500 then it goes crazy. Told me over 17moa drop and it was really 10.5.

160gr Nosler accubonds. I’m U3.7 MOA at 500 yds. I’m sighted in 3”s high at 100.

 

[BuzzH]

Twisting turrets?

If so, scope adjustment value may not be precise, you might not be in the center of windage, etc....

 

[MITCHMO]

Twisting turrets?

If so, scope adjustment value may not be precise, you might not be in the center of windage, etc....

Yea I guess I should have mentioned the optics. Waiting on a new Leupold to arrive but I’m using a Burris veracity with adjustable turrets as my means to compensate. I guess I never considered the adjustment of the dial to be the inaccurate part. Makes sense though. Hopefully more ammo shows up soon and I’ll try to get 5 shot groups every 100 yards from 200-600 and see what it looks like. I’ll run it through my cheap chrono and see if that’s consistent as well.

 

[MITCHMO]

160gr Nosler accubonds. I’m U3.7 MOA at 500 yds. I’m sighted in 3”s high at 100.

I’ll have to try those 160’s. I’ve got three boxes of 168 ABLR For my 7mag I’ve been reloading with and really like them. Time to order more stuff!

 

[marksjeep]

Might try plotting with your bullet drop as negative values to flip the graph. There is a hook in your empirical curve at about 475, ditto above, would want to see shot data.

 

[Fire_9]

You need to remember that ballistic calculators are no different than any other equation, garbage in=garbage out. You either need to tweak some of your variables or like Buzz mentioned, your scope adjustments aren’t what they say they are. Are you shooting through a chrono? Do you have a bubble level?

 

[BuzzH]

Another possibility is your scope isn't level, or you're canting your rifle as well...adjustment values are compromised if you're not level with planet earth.

 

[Durango Mike]

I think you are way overthinking this, while fun to do anticipating a hunt, my 280 AI is sighted 2 1/2 inches high at 100, using Barnes TSX 150 gr at 3050fps and know I am good for a heart / lung shot to 350 on mule deer and 400 on elk holding on hide, after that energy starts to drop off which makes me reluctant to shoot beyond that. Was helping a guy last year and he spent so much time dialing in his 225 yard broadside on a large cow he missed the easy standing opportunity and shot under at 300 ish quartering away. He shot one the next day at 125 in our bottom pasture and waited for the good angle and did no dialing. I have never had to shoot an elk over 250 yards, took a nice muley at 300 ish and try to avoid long shots as wind in the mountains can cause way more long misses than elevation in my experience. My thought is shoot at long range with improvised rest like your pack with your body at an odd angle and see just how far you are comfortable and work on that basis, you might find that consistantly hitting a 10 inch pie plate at 500 yards under hunting conditions is tough, try climbing 10 flights of stairs before you do to make it more interesting. I find keeping things simple works best for me, have fun working up loads and anticipating your hunt!

 

[matt0550]

other points to consider...
Is this scope 1st or 2nd focal plane (in the case where you are utilizing a ballistic reticle or stadia lines for hold), are you adjusting parralax?

The best I have ever done with out of the box ballistic calculators has been with the Applied Ballistics app where I have downloaded the CDM (custom drag model) for the projectile I was using. This is a model created out of true shooting data from Brian Litz and company and for my $.99 I got true dope out to 1000 yards with the only variation being environmental factors or shooter error

 

[The Hedgehog]

I think you are way overthinking this..

I think you are way underthinking this.

Maybe he's got a perch he wants to hunt that could include a 600-700 yard shot. Those are certainly doable with good equipment and some practice. He didn't post asking how far folks are reluctant to shoot at..