Help Interpreting DOPE

[FourT6and2]

Just got my rifle re-barreled and I'm looking for some help interpreting my newest DOPE out to 1,000 yards. As you can see, starting at 800 yards there is a 0.3 MIL discrepancy between calculated come-up and actual that stayed consistent over every shot. I put at least 10 rounds downrange at each distance. Looks like my rounds are shooting a bit flatter past 700-800 yards than what my ballistic calculator is telling me (Trasol). So what does this tell you? Should I bother trying to true my profile in Trasol or just dial 0.3 MIL less in the future? Are these results too small to worry about or is there something I should be aware of?

Bartlein M24 barrel
26"
1:8 twist
4-groove
Chambered in 6.5 Creedmoor
Shooting factory ammo: Hornady 140gr. ELD-M

Zero: 101 yards
DA: 1083 ft.
Sight height: 2"
Average muzzle velocity: 2669 fps
Bullet length: 1.318"
G7 BC: 0.312

DISTANCE / DENSITY ALTITUDE — CALCULATED COME-UP in MRAD/MIL (ACTUAL COME-UP)

200 Yards / DA: 1140 — 0.48 (0.5)
300 Yards / DA: 1300 — 1.2 (1.2)
425 Yards / DA: 1600 — 2.26 (2.3)
500 Yards / DA: 1200 — 2.97 (3)
600 Yards / DA: 1640 — 3.98 (4)
800 Yards / DA: 1900 — 6.31 (6)
900 Yards / DA: 2300 — 7.61 (7.3)
1000 Yards / DA: 2400 — 9.06 (8.8)

 

[_Windrider_]

Just got my rifle re-barreled and I'm looking for some help interpreting my newest DOPE out to 1,000 yards. As you can see, starting at 800 yards there is a 0.3 MIL discrepancy between calculated come-up and actual that stayed consistent over every shot. I put at least 10 rounds downrange at each distance. Looks like my rounds are shooting a bit flatter past 700-800 yards than what my ballistic calculator is telling me (Trasol). So what does this tell you? Should I bother trying to true my profile in Trasol or just dial 0.3 MIL less in the future? Are these results too small to worry about or is there something I should be aware of?

Bartlein M24 barrel
26"
1:8 twist
4-groove
Chambered in 6.5 Creedmoor
Shooting factory ammo: Hornady 140gr. ELD-M

Zero: 101 yards
DA: 1083 ft.
Sight height: 2"
Average muzzle velocity: 2669 fps
Bullet length: 1.318"
G7 BC: 0.312

DISTANCE / DENSITY ALTITUDE — CALCULATED COME-UP in MRAD/MIL (ACTUAL COME-UP)

200 Yards / DA: 1140 — 0.48 (0.5)
300 Yards / DA: 1300 — 1.2 (1.2)
425 Yards / DA: 1600 — 2.26 (2.3)
500 Yards / DA: 1200 — 2.97 (3)
600 Yards / DA: 1640 — 3.98 (4)
800 Yards / DA: 1900 — 6.31 (6)
900 Yards / DA: 2300 — 7.61 (7.3)
1000 Yards / DA: 2400 — 9.06 (8.8)

How are you getting a 1000 ft variation in DA from 200-1000? My advice, use mark and franks gravity ballistics to dope your rifle then true up your calc. Don’t look at a calc until you’ve done that. Use pressure temp and humidity instead of DA.

 

[FourT6and2]

How are you getting a 1000 ft variation in DA from 200-1000? My advice, use mark and franks gravity ballistics to dope your rifle then true up your calc. Don’t look at a calc until you’ve done that. Use pressure temp and humidity instead of DA.

Temperature. It gets hotter as the sun rises lol...

Shooting at physically different locations and time. Cold in the morning and then as the sun rises, it's getting hotter. About 10 minutes at each firing line from 200 yards to 1,000. Not shooting in one spot at targets at different locations. Shooting at different locations at one target. That's how this shooting range works. You shoot for about 10 minutes at 200 yards, then walk out to 300 yards. Shoot for a few minutes, walk out to 425, etc. It was about 48 F. in the morning and by the time we got out to 1,000 yards it was 75 F.

I can try using temp/pressure/humidty next time. But we only get one chance per month for a practice shoot out to 1,000 yards. And we only have about 8-10 minutes at each distance. So it's hard to sit there and record temp, pressure, humidty and whatnot.

I might try to visit another range that has steel targets out various distances out to 1200 yards from one firing line. That way I can take shots at different distances back to back.

 

[_Windrider_]

Just as a reference it takes 15 degrees F to move DA 1000 feet. That’s one reason I asked. My issue with DA is this, a given DA can be derived from multiple combinations of the three variables. One day 2000DA could be from high temp and low pressure the next high pressure and low temp. That changes your velocity. DA is awesome in a hasty field card for sure but when gathering actual dope I prefer to track the 3 variables separately.

Now, when gathering dope, you true your calculator to real world not try and match your real world to the calculator. Don’t look at a calculator till you’ve doped it out. Then tweak the calculator to match your real world by modifying velocity and BC if necessary.

Also, a 1000 ft DA change wouldn’t cause that.

 

[FourT6and2]

Just as a reference it takes 15 degrees F to move DA 1000 feet. That’s one reason I asked. My issue with DA is this, a given DA can be derived from multiple combinations of the three variables. One day 2000DA could be from high temp and low pressure the next high pressure and low temp. That changes your velocity. DA is awesome in a hasty field card for sure but when gathering actual dope I prefer to track the 3 variables separately.

Now, when gathering dope, you true your calculator to real world not try and match your real world to the calculator. Don’t look at a calculator till you’ve doped it out. Then tweak the calculator to match your real world by modifying velocity and BC if necessary.

Also, a 1000 ft DA change wouldn’t cause that.

I don't understand what you're saying. My real-world data is listed above. Ignore the calculator and DA then.

Try (Actual):

200 Yards: 0.48 (0.5)
300 Yards: 1.2 (1.2)
425 Yards: 2.26 (2.3)
500 Yards: 2.97 (3)
600 Yards: 3.98 (4)
800 Yards: 6.31 (6)
900 Yards: 7.61 (7.3)
1000 Yards: 9.06 (8.8)

I looked at the Gravity Ballistics worksheet and tried it but it, but I guess I don't understnad it because the numbers don't seem to make sense. For example, my try data for 300 yards matched my actual real-world come up of 1.2 MIL. If I enter that number into that worksheet, it tells me that at 1,000 yards I should dial 10.5 MIL. But if I do that, I'd shoot more than 52 inches over my target.

Gravity Ballistics worksheet doesn't take environmentals into account. Here in California, the tempure swings more than 30 degrees in 1-2 hours. That affects ballistics.

Let's say using my ballistic calculator at 300 yards with a DA of 1300, it spits out 1.2 MIL. I dial and boom... spot on. Great. 1.2 MIL is confirmed. I then immediately look at 1,000 yard number using the same DA: 9.22 come up. That's a little closer to what Gravity Ballistics worksheet says, but still more than 40 inches too high! But in the real world, there was about a 30-minute time gap between when I shot at 300 yards vs 1,000. And in that time, the temp rose by almost 30 degrees and DA went to 2400. But Gravity Ballisitcs number says come up should be 10.5 MIL, which is just silly.

What would need to happen is I would have to shoot at 200 yards AGAIN, before calculating elevation at 1,000. Because then the real-world data at 200 would reflect the temp/DA change.

Anyway... my ballistic calculator seems to be spot on out to 600 yards. And then at 800-1000 (no 700-yard data), it's 0.3 MIL off. I'm guessing it's because of temperature. By the 800-yard line, it was getting much warmer (full sun).

 

[_Windrider_]

I’ll write a better post later when I’m not on my phone. Someone will probably have some feedback in the meantime. I’ll do my best to make my point more clear and concise when I can type on a keyboard.

 

[FourT6and2]

Ok, I appreciate it

 

[FourT6and2]

I think I figured it out. It's probably down to BC.

I've been using a G7 BC of 0.312 for years and it's typically worked. This is what Hornady published when they first released the 140gr ELD-M. Their website now lists the BC as 0.326. I'm betting if TRASOL had the ability to input progressive BC, the data would line up past 600 yards. If I go in and change the BC for calculations past that distance, they line up as expected for corresponding environmentals.

 

[Sig Marine]

You found your answer. I used 0.326 in Shooter and all but a couple lined up (those that varied were only by 0.1 mil).

 

[Makinchips208]

I think the instructions per either the article or maybe a video were,

True the velocity with your 600 yard dope.
Then use the 800 or 1000 yard dope to true the bc.