Bad bc or...?

[doc holiday13]

Got to stretch my 7 prc today and I had mixed results.

Gun is zeroed. ballistic data recorded in AB. 7mm 175ELDX.

took the gun out today to shoot beyond 200. First target 800 yards. AB says 4.7mils. Boom .. 3 shots impact on target.
Next target 1242 yards. AB says 8.7mil boom... way low. .5mil low. for all shots. WTF?? walked the bullet in. First .3 mils then added .2 mil. is this a bullet issue??. I'm never gonna shoot an animal that far but I at least want my data to work and my ability to shoot be the reason I miss the target

any ssuggestions

 

[wapitibob]

You need to true the bc when shooting 1000+.

 

[eric1115]

Got to stretch my 7 prc today and I had mixed results.

Gun is zeroed. ballistic data recorded in AB. 7mm 175ELDX.

took the gun out today to shoot beyond 200. First target 800 yards. AB says 4.7mils. Boom .. 3 shots impact on target.
Next target 1242 yards. AB says 8.7mil boom... way low. .5mil low. for all shots. WTF?? walked the bullet in. First .3 mils then added .2 mil. is this a bullet issue??. I'm never gonna shoot an animal that far but I at least want my data to work and my ability to shoot be the reason I miss the target

any ssuggestions

Environmentals spot on (do you use DA or actual temp/pressure? Station pressure vs corrected?)?

How did you measure velocity?

How solid is your zero? Same shooting position as your shots at distance?

What scope? Have you checked tracking?

I'd check all those pretty carefully before adjusting BC.

 

[alexnelon]

Got to stretch my 7 prc today and I had mixed results.

Gun is zeroed. ballistic data recorded in AB. 7mm 175ELDX.

took the gun out today to shoot beyond 200. First target 800 yards. AB says 4.7mils. Boom .. 3 shots impact on target.
Next target 1242 yards. AB says 8.7mil boom... way low. .5mil low. for all shots. WTF?? walked the bullet in. First .3 mils then added .2 mil. is this a bullet issue??. I'm never gonna shoot an animal that far but I at least want my data to work and my ability to shoot be the reason I miss the target

any ssuggestions

What scope are you using?

Have you checked to make sure it’s actually dialing accurately?

A lot of scopes have problems getting through the full range without binding up.

Also 7 prc is notoriously slower than box velocity so if you haven’t chrono’d I would do that too.

BC is pretty low on the list of things to check.

 

[Wrench]

Environmental can play hell too.

I like to take the rifles right out to the transonic and verify.....then back my way in. When you start beating on 16-1800 and working in, 800 will be a breeze compared to working out.

On our 18 and 2200 steel a local call on the kestrel may be 1.2M R.....but then the impacts show us that were actually 2.5 L on the target. We shoot across 2 deep draws that face east and are a BITCH to read in the morning.

 

[doc holiday13]

My speeds were all checked and verified with the garmin unit.. These are handloads so I'm not going off the box.

800 yards is generally the yardage where you should be able to verify BC. At 1242 yards the velocity was still above 1400 for definite, I saved all my environmentals(temp, humidity, altitude, pressure) and recorded speeds at the time of this event. So I'll attempt to see if a drop chart correction will work because velocity calibration is not a viable solution(this method claims my MV was almost 100 fps slower). I haven't done a tracking test recently on the scope; its US Optics from 2010.