Bullet trajectory question

[bonecollector777]

So I've been shooting my brothers new 6.5 creedmoor with factory precision hunter 143 eldx bullets. Chrono shows about 2640 fps with a 24 inch barrel box says 2700 with a 26 inch barrel. Either way with a 200 yard zero and inputting 2640 fps I'm nailing where I'm supposed to at 500 but out at 800 I'm hitting a constant 10 inches high. When I try and adjust for 10 inches at 800 that puts my 500 off by about 3 inches. Any ideas what's Up? I'm gonna shoot some more just to verify but could the bc be off?

[trphyhntr]

So I've been shooting my brothers new 6.5 creedmoor with factory precision hunter 143 eldx bullets. Chrono shows about 2640 fps with a 24 inch barrel box says 2700 with a 26 inch barrel. Either way with a 200 yard zero and inputting 2640 fps I'm nailing where I'm supposed to at 500 but out at 800 I'm hitting a constant 10 inches high. When I try and adjust for 10 inches at 800 that puts my 500 off by about 3 inches. Any ideas what's Up? I'm gonna shoot some more just to verify but could the bc be off?

Idk if I'm 10" high at 800 I call it good af

[bigorange]

Which rifle? Shooting same ammo in Ruger American Predator and will be interested in how this works up. Another guy at the range was putting same ammo through chrono with the Predator getting 2580 fps.

[firstcoueswas80]

Assuming you're using turrets, just change where your turret is set and go with it

[308Nut]

So I've been shooting my brothers new 6.5 creedmoor with factory precision hunter 143 eldx bullets. Chrono shows about 2640 fps with a 24 inch barrel box says 2700 with a 26 inch barrel. Either way with a 200 yard zero and inputting 2640 fps I'm nailing where I'm supposed to at 500 but out at 800 I'm hitting a constant 10 inches high. When I try and adjust for 10 inches at 800 that puts my 500 off by about 3 inches. Any ideas what's Up? I'm gonna shoot some more just to verify but could the bc be off?

 

Are you accounting for barometric pressure? Temperature? If you're not factoring those (among other factors), then that is likely why you're high at 800. Out to 500, these matter much less. At 800, air density matters in a very large way.

 

Hornady's BC values for their ELD line are incredibly accurate.

[pwrguy]

not familiar with the bullet or cartridge. What is the published BC and what are you actually using? Possibly your bullet is moving a little quicker than you have it on the chrono?

[WHT_MTNMAN]

There are many more people with much more knowledge than me but I usually just assume that it is me just having one of the many variables (sight height, BC, etc...) inputed incorrectly. At that point I adjust my velocity to match my real world shots and verify at all ranges. I can then input this data into almost any program and adjust for conditions.

[bonecollector777]

Bigorange it is a semi custom Remington 700. The ballistic calculator I'm using is accounting for elevation, temp, and pressure. I'm using Leica HDB binos as well with ballistic compensation and info is entered correctly on the sd card I entered into it. It's like the bullet isn't dropping as much as it thinks it is after 500 yards. I can't tweak my speeds to keep my 500 the same and drop my 800. Possibility that the binos aren't correctly compensating for the variables but the click value it spit out matches up with the ballistic app info. I'll shoot some more and tweak a few things and see if I can get it figured out. Thanks guys

[STOMP442]

Scope height is a big factor that is often overlooked. Most programs assume a sight height of 1.5" when in reality most set ups are closer to 1.8". BC is also one thing to look at. Are you using an average BC value or the highest one printed on the box? Are you using the G7 drag model or the G1. You should be using the G7 for that bullet and the rages in which you are shooting. Hornady lists a G1 of .623 and G7 of .314 for that bullet. But the Average numbers are .603 and .304 respectively and cause some discrepancy at longer ranges. The other issue may also be with the scope. The adjustments marked on the turrets may say 1/4" at 100 yards but the actual adjustment may be slightly more or slightly less and will compound at longer ranges if not accounted for.

[bigorange]

There are many more people with much more knowledge than me but I usually just assume that it is me just having one of the many variables (sight height, BC, etc...) inputed incorrectly. At that point I adjust my velocity to match my real world shots and verify at all ranges. I can then input this data into almost any program and adjust for conditions.

Sounds like me...I probably need to take this approach.

[AzDiamondHeat]

Just shoot the critter at 500....lol

[bonecollector777]

Scope height is a big factor that is often overlooked. Most programs assume a sight height of 1.5" when in reality most set ups are closer to 1.8". BC is also one thing to look at. Are you using an average BC value or the highest one printed on the box? Are you using the G7 drag model or the G1. You should be using the G7 for that bullet and the rages in which you are shooting. Hornady lists a G1 of .623 and G7 of .314 for that bullet. But the Average numbers are .603 and .304 respectively and cause some discrepancy at longer ranges. The other issue may also be with the scope. The adjustments marked on the turrets may say 1/4" at 100 yards but the actual adjustment may be slightly more or slightly less and will compound at longer ranges if not accounted for.

I checked scope height just now and it's right at 1.5 inches. Sounds like I just need to start eliminating different variables one by one and see what's up. Thanks for all the info. And more than likely won't be shooting any animals at more than 600 anyway so if worst comes to worst we will make sure to just get closer.

[300RUM]

Another thing to check is decimals in your data entry. Make sure they are not misplaced, missing or entered where there should not be one. It is an easy one to miss. I once entered a 0.6 FPS per degree powder temp correction as 6. It really screwed things up.

[STOMP442]

 

Scope height is a big factor that is often overlooked. Most programs assume a sight height of 1.5" when in reality most set ups are closer to 1.8". BC is also one thing to look at. Are you using an average BC value or the highest one printed on the box? Are you using the G7 drag model or the G1. You should be using the G7 for that bullet and the rages in which you are shooting. Hornady lists a G1 of .623 and G7 of .314 for that bullet. But the Average numbers are .603 and .304 respectively and cause some discrepancy at longer ranges. The other issue may also be with the scope. The adjustments marked on the turrets may say 1/4" at 100 yards but the actual adjustment may be slightly more or slightly less and will compound at longer ranges if not accounted for.

I checked scope height just now and it's right at 1.5 inches. Sounds like I just need to start eliminating different variables one by one and see what's up. Thanks for all the info. And more than likely won't be shooting any animals at more than 600 anyway so if worst comes to worst we will make sure to just get closer.

 

How did you measure your scope height? I have set up literally hundreds of rifles and the closest I have ever got to 1.5" is 1.6" with a 40mm objective. What scope and rings are you using? If it's a scope with a 50mm objective you are going to be at least 1.7" above the bore line. The correct way to measure scope height is to take your calipers and measure the diameter of your scope bell and divide that number by two. Then measure the diameter of your barrel just in front of your objective bell and divide that number by two. Then measure the gap between the scope bell and the top of your barrel and add all those numbers together. This will give you an accurate sight height from center of bore to center of scope tube.

 

For example:

Scope bell dia = 2.228 divided by 2 = 1.114

Barrel dia at scope bell = .864 divided by 2 = .432

Gap between scope and barrel = .167

 

Sight height = 1.713"

[DesertBull]

Just because your scope MFG says your clicks are 1/4 MOA or 1/10th MIL at 100 does mean it actually is.