Help - Ballistic Calculator off from Actual Dope

[Tubb2402]

I need some help with getting my rifle dialed in.

So for clarity here is my setup. I have a 308 Howa Alpine Mountain Rifle 20" barrel with VX-5 scope and have been shooting Nosler Factory Ammo 168 E-Tips. I have it sighted in at 100 yards and ran 5 bullets through a chronograph averaging about 2650. The E-Tips have BC .503 and my temp this time year is about 90 degrees. My elevation is about 250 feet.

Problem - The Nosler ballistic calculator does not even come close to actual dope. Below is the Calculator vs Actual.

I put it in a sled and it will have bullets touching, but does not come close to calculator. I've tried several different boxes to make sure it wasn't ammo. I've been out on 2 occasions and had the same results.

The only thing I can figure is either the Chrono was off or the scope is off somehow. Any thoughts on why this would be so far off?

I did do the math and if the chrono was off it would put my velocity at 2200 which seems low for the Nosler factory ammo which says it should be 2750.

Yardage	Calculator	Actual
100	0	0
200	1.97	6
300	4.68	7.5

 

[JLS]

Get the gun out of the sled and base your chart off actual drops.

 

[Coach Chris]

Is the calculator set for milliradian?

 

[okie_hotrod]

Yea... something is waaay off. I plugged into BallisticsARC and got similar results. I would change the battery in your chrono, make sure you have your sunscreens on, and shoot it again. Try shooting with a bipod and rear bag instead of a lead sled, a lead sled isn't gonna tell you if you're pulling shots. Also double check all your screws for tightness. The most important thing when getting drop data is keep everything as consistent as humanly possible.

 

[VikingsGuy]

...

 

[cahunter805]

Ditch that lead sled!! Seems like so many on this forum and others use them. They are worthless junk!
Shoot it from a stable bench or from prone with a rear bag and bipod or front rest. Get a solid shooting position and then test drops again.
Your velocity seems pretty good and on par for a 20" barrel.

 

[Tubb2402]

Thanks for the comments . But unfortunately I’ve had the same results in the sled and setting up solid only using my bag on a good bench.

 

[Tubb2402]

Is the calculator set for milliradian?

No im using MOA.

 

[jnagel32]

I don’t know if this is your problem or not, but I ran into a similar circumstance when I was developing a load for my rifle. I was getting 3050 FPS on a buddy’s chrono. It was a few MOA off what StrelokPro was saying. Well got a different chrono and figured out it was actually averaging 2952 FPS. Now it is right on what StrelokPro says.

 

[Rifles And More]

Yardage	Calculator	Actual
100	0	0
200	1.97	6
300	4.68	7.5

I need labels: MOA, Clicks, Inches ?

I will guess MOA based on what I ran on JBM.

200 yards would be a 4" drop and approx 2 MOA adjustment or 8 clicks.
300 yards would be a 15" drop and approx 5 MOA adjustment or 20 clicks.

6 MOA adjustment would be 12" at 200
7.5 MOA would be 22.5" at 300

6 clicks would be 1.5 MOA at 200 or 3" drop
7.5 clicks (can't even do 1/2) at 300 would be about 6" at 300.

I may have confused myself with all the above gibberish, and may have made a mistake. But, I'm not sure we are comparing apples to apples.

Have you shot a group at 200 without making adjustments? What are the actual drops in inches?

 

[VikingsGuy]

Your velocity seems about right. The factory number is 2,750 and those are typically 24" or 26" test barrels, so 2,650 out of your 20" is reasonably in the ballpark. Also, confirmed you calculations on JBM and that is good. Something is wrong with your actual numbers regardless of actual velocity - no way a .308 at 2700-ish only drops 1.5 MOA over the course of travel from 200y to 300y (i had to set to 4,000fps in JBM to have that flat a trajectory for a 168 grain e-tip zeroed at 100). With such a significant gap between "actual" and realistic expected, I typically think human error first, scope problem second, ammo/velocity/bc problems as very distant thirds. Just doesn't seem like ammo or velocity is the issue here.

Scope issues would be those that create some significant parallax problem (not the little parallax you get in a 100y factory setting on 300y shot that your objective may allow you to adjust for, but gross lack of parallelism with scope and barrel as mounted). Things like loose base, loose rings, incorrectly oriented rings, mis-matched rings, poor scope base bedding, wrong rings/base for particular action, incorrectly oriented base, damaged scope internals, damaged tube, etc.

 

[Tubb2402]

I need labels: MOA, Clicks, Inches ?

I will guess MOA based on what I ran on JBM.

200 yards would be a 4" drop and approx 2 MOA adjustment or 8 clicks.
300 yards would be a 15" drop and approx 5 MOA adjustment or 20 clicks.

6 MOA adjustment would be 12" at 200
7.5 MOA would be 22.5" at 300

6 clicks would be 1.5 MOA at 200 or 3" drop
7.5 clicks (can't even do 1/2) at 300 would be about 6" at 300.

I may have confused myself with all the above gibberish, and may have made a mistake. But, I'm not sure we are comparing apples to apples.

Have you shot a group at 200 without making adjustments? What are the actual drops in inches?

Sorry the confusion, I'm talking MOA as that is what is on my dial. At 200 yards I had to turn the dial to 6 MOA and at 300 yards 7.5 MOA to get it to hit center target. The rifle has always made nice groups but the Calculator vs Actual MOA are just way off.

 

[Tubb2402]

Your velocity seems about right. The factory number is 2,750 and those are typically 24" or 26" test barrels, so 2,650 out of your 20" is reasonably in the ballpark. Also, confirmed you calculations on JBM and that is good. Something is wrong with your actual numbers regardless of actual velocity - no way a .308 at 2700-ish only drops 1.5 MOA over the course of travel from 200y to 300y (i had to set to 4,000fps in JBM to have that flat a trajectory for a 168 grain e-tip zeroed at 100). With such a significant gap between "actual" and realistic expected, I typically think human error first, scope problem second, ammo/velocity/bc problems as very distant thirds. Just doesn't seem like ammo or velocity is the issue here.

Scope issues would be those that create some significant parallax problem (not the little parallax you get in a 100y factory setting on 300y shot that your objective may allow you to adjust for, but gross lack of parallelism with scope and barrel as mounted). Things like loose base, loose rings, incorrectly oriented rings, mis-matched rings, poor scope base bedding, wrong rings/base for particular action, incorrectly oriented base, damaged scope internals, damaged tube, etc.

Thanks I'm going to take off the scope and bases, and start over. Double checking to make sure everything is good. Hopefully I'll find a loose screw or something and this will be an easy fix. If not I'll have to send in the scope to Leupold and see if they find a problem with the scope.

 

[cahunter805]

Something is definitely not right especially with only 1.5MOA difference from 200 to 300. Checking your bases and rings and screws and remounting the scope would be a good start. Next once you get it zeroed at 100 yards are you zeroing the turret correctly? Another test would be not to dial but shoot a group at 200 and 300 and measure your actual drop first. Then you will know if your scope is to blame. I highly doubt it's the ammo.

 

[Cerebral Stalker]

Something is definitely not right especially with only 1.5MOA difference from 200 to 300. Checking your bases and rings and screws and remounting the scope would be a good start. Next once you get it zeroed at 100 yards are you zeroing the turret correctly? Another test would be not to dial but shoot a group at 200 and 300 and measure your actual drop first. Then you will know if your scope is to blame. I highly doubt it's the ammo.

That's exactly what I would be doing in your situation.

 

[JLS]

I didn’t realize you were dialing. Chasing two variables at a time will get you nowhere. Test one variable first (ammo) by shooting without dialing, as suggested above. Once you eliminate a variable, test another.

 

[Bigjay73]

Nothing to do with your problem, but Nosler is notorious for BS BCs. I ain't bashing, I pretty much only reload with Nosler bullets, but when you get your issue fixed, it can throw off ballistic calculations.

 

[1_pointer]

I didn’t realize you were dialing. Chasing two variables at a time will get you nowhere. Test one variable first (ammo) by shooting without dialing, as suggested above. Once you eliminate a variable, test another.

This! Tall target and no dialing will help you determine if it's a ballistics conundrum or a scope conundrum. I'm betting on the latter...

 

[Tubb2402]

This! Tall target and no dialing will help you determine if it's a ballistics conundrum or a scope conundrum. I'm betting on the latter...

Thanks for the all the input, I really appreciate it. I plan to take bases, rings, and scope off tonight, clean them, and then put all back on to spec. After that I'll head out to the range and sight in at 100yds. Then I'll let barrel cool down completely and do 2 tall target test. Letting the barrel cool down between each test.

1st Tall Target Test for Ammo: Shoot a group of 3 for each at 100yds, 200yds, and 300yds with no dialing all aiming at the same spot. Then measure distance between groups.

2nd Tall Target Test for scope: Shoot 3 groups of 3 all at 100yds with no dialing on first group, 10 MOA dial at second group and, another 10 MOA (20 MOA total) for 3rd group. Then Measure distance between groups.

I suspect either I did something wrong when mounting scope or something internally on the scope. Either way I need to get it done so that if something is wrong internally with scope Leupold can get it back to me prior to rifle season.

 

[JLS]

I know this was asking the very obvious, but are you counting clicks or MOA? The VX5 is 1/4 MOA clicks, correct?