Yet another tuning/dope question

[DocRDS]

Been doing a ton of work at 1000.

I'm pretty rock solid with that 1000 yard dope.
Problem: It FUBARS my weaponized math DOPE as in I cannot get my kestrel to line up in any reasonable sense my 200 yard to 900 yard data.

My 2-9 was done this summer during class. Had it all trued up on the AB kestrel (including 1000 yard at 8.5 mils)

This winter I was shooting 1000 yards all winter long (weekly event) and I am dead nuts on a 9.0 mils. Now i can play with my BC and MV all I want, but this number is incompatible with all my previous data (same ammo and gun--DA has between 0 and 2000). However, given I have multiple sessions and maybe 150+ rounds at 1000, this 9.0 is pretty dialed in. Going back on my DOPE, if I true up for the 1000, my kestrel is high starting around 400 missing by a few tenths in the latter stages, but that is well within my "shooting error".

So am I chasing my tail here? I've flipped between G1 and G7, screwed with the MV to hell and gone, as well as the BC--our range gives MV at 1000, so I am close to that (MV) along with the 1k dope. I had my kestrel trued from this summer based on Data, but this new point refuses to budge, despite my best efforts to think otherwise. My "new" 1000 yard dope at this range is 9.0 mils and there is no way to synch this up with previous data without a HUGE shift in BC. I'm at 28-30 inchs at 1000 so plenty of me work to do.

Incidently 4DOF gives a pretty solid prediction with a Form Factor of 1.1, so maybe just a custom curve on the Kestrel?

If I ever get back on a range with 200-900 I could just verify, but alas, new area and I have no access to that.

 

[moaorbust]

I believe you may be running into reality versus the mathematical curve models we use. A particular drop is only accurate between a specific set of distances on a curve model so you have to pick one to optimize for. There is a really awesome video I saw two months ago that explains it. I think Hornady made the video and I will look for it unless someone posts it first.

Found it. https://www.snipershide.com/shooting/threads/i-was-wrong-and-hornady-proved-it.7146329/

 

[OREGUN]

Are you saying your groups at 1000 are 28-30”? If that’s the case, that’s damn near a mil. So for any given shot, your half mil difference between 8.5 and 9 is lost in your own static.

So now that you’ve fiddled everything, you could be a few tenths of here and there at the intermediate distances and not really be seeing it…and thus be off a half mil at 1000 and not really know what your waterline dope is.

If that’s not what the 28-30 sentence means then I apologize and will go back to my beer.

 

[DocRDS]

Are you saying your groups at 1000 are 28-30”? If that’s the case, that’s damn near a mil. So for any given shot, your half mil difference between 8.5 and 9 is lost in your own static.

So now that you’ve fiddled everything, you could be a few tenths of here and there at the intermediate distances and not really be seeing it…and thus be off a half mil at 1000 and not really know what your waterline dope is.

If that’s not what the 28-30 sentence means then I apologize and will go back to my beer.

Nah I wasn't super clear---yes my "group" was 28 inch (plus me fucking with elevation--point being I can tell my waterline at 1000) but most of that is either wind or me moving impact left or right (mostly calm, so i bet its me). My vertical dispersion is small enough that I can definitly call the waterline at 9 mil. Yes I have to get my spread down, but I think thats me

Actually my worry is that my 200-900 is off. I feel very good about 1k. Nov to Today--dial 9: WHACK (adjust for L/R)
For F-class I score I was at 170 3X, even with my changes in elevation

Crude rought painting of 9 mil setting string (I can see the diff in 8.6 (blue) vs 9.0 vs 9.2 (red) on the target:

 

[6.5SH]

Post up the rest of your data so it can be examined and compared in other apps.

 

[OREGUN]

Excellent. So you are getting bullet velocity at 1k off the scoring system? Do you have a chronograph you can get MV at the muzzle? Have you told the kestrel that the MV value you are using is at 1000? Not sure that’s a thing…it would be a “chronograph distance from the muzzle” type option. My guess is that your Dope for 200-900 probably is off. You know 9 is good at 1000 but until you shoot the others again, it’s just a wag. We can put your values into our calculators all day but it’s an exercise in guessing.

The “Why” is a different qustion. Maybe a change in muzzle velocity…new powder lot?…big change in temps?…f-open off a rest using essentially a free recoil vs something else at the intermediate ranges last summer… barrel changing as it broke in?

It’s probably a few subtle things all together. A few tenths here and there, a slightly off MV value, a BC thats not holding up quite as well as the box suggests as the distances increase. If you‘re mostly shooting at 1000, you‘re good to go until you have a chance to shoot at 4, 6, and 8 again. What cartridge are we talking about?

 

[DocRDS]

6.5 Creed. Factory Hornady ELD-M 140. Do not have a MV as I was moving at the time.
My best guess is the MV is around 2700 (Standard ATX rifle with factory barrel 26 inch I think)

I've essentially shot everything prone off bipod (even though we 'score' F-class, in reality, its just practice, some guys bench--I'm a belly flopper, so I shoot prone and the electronic scoring is SUPER handy for nearly instant feedback.

40 shots yesterday had 1000 yard avg Velocity of 1370 fps (13 SD)
All units are mils and Yards.

1000 (now) 9.0 (80 rounds data) Round count about 400
-----
Previous: Round count about 60-150
1-5 rounds of data--shorter ranges tend to have 5 shots, longer ranges 1-2 shots
1000 (prev) 8.5 (possible angle shot, 5 degrees down, swirling wind on rolling terrain)
900 7.0
800 5.8
700 4.7
600 3.6
500 2.6
400 1.7
300 1.0
200 0.2

Writing this out as a Statistician and "Beleive the bullet" seems I should weight the new data more heavily until I get some feedback on the earlier intermediate ranges. I can wish all I want, but everything I have experienced says 9.0 is my dope at 1k, despite earlier data that says 8.5

Still also could be me--give that I am developing, I could of jerked the earlier shots high and I have 9 months of dry/live practice. That rifle doesn't move anymore when I "misfire"--pull trigger on a chamber I think is loaded but is empty.

 

[6.5SH]

What was the environmental data for your old and new sessions/locations?

 

[OREGUN]

6.5 Creed. Factory Hornady ELD-M 140. Do not have a MV as I was moving at the time.
My best guess is the MV is around 2700 (Standard ATX rifle with factory barrel 26 inch I think)

I've essentially shot everything prone off bipod (even though we 'score' F-class, in reality, its just practice, some guys bench--I'm a belly flopper, so I shoot prone and the electronic scoring is SUPER handy for nearly instant feedback.

40 shots yesterday had 1000 yard avg Velocity of 1370 fps (13 SD)
All units are mils and Yards.

1000 (now) 9.0 (80 rounds data) Round count about 400
-----
Previous: Round count about 60-150
1-5 rounds of data--shorter ranges tend to have 5 shots, longer ranges 1-2 shots
1000 (prev) 8.5 (possible angle shot, 5 degrees down, swirling wind on rolling terrain)
900 7.0
800 5.8
700 4.7
600 3.6
500 2.6
400 1.7
300 1.0
200 0.2

Writing this out as a Statistician and "Beleive the bullet" seems I should weight the new data more heavily until I get some feedback on the earlier intermediate ranges. I can wish all I want, but everything I have experienced says 9.0 is my dope at 1k, despite earlier data that says 8.5

Still also could be me--give that I am developing, I could have jerked the earlier shots high and I have 9 months of dry/live practice. That rifle doesn't move anymore when I "misfire"--pull trigger on a chamber I think is loaded but is empty.

A couple of things immediately jump out.

Your barrel wasn’t broken in when you got your previous dope so that data is highly likely to be slightly off. Not all barrels, but many, will have slightly different MV after 200 ish rounds. A 7mm barrel I just spent some time with was giving me 2865 initially and 2910 after around 180 rounds at the same charge weight, for example.

Dope truing should be done in the most ideal conditions you can get so downhill, with wind, over rolling terrain is not likely to be the best data. It’s credible, but should be verified.

9 mil at 1000 under the typical atmospherics you are shooting in is THE ONLY THING you know for certain. Your previous dope is likely pretty close but I wouldn’t bet the championship on a single shot at a small target at 700 yards based on it.

 

[OREGUN]

I know it’s sacrilege to say this around here but I’ve had surprisingly accurate results with 6 cm Hornady factory ammo by just using box MV and BC. Out of curiosity, plug those values into the kestrel and see what the 1000 yard number looks like.

 

[6.5SH]

I know it’s sacrilege to say this around here but I’ve had surprisingly accurate results with 6 cm Hornady factory ammo by just using box MV and BC. Out of curiosity, plug those values into the kestrel and see what the 1000 yard number looks like.

His weaponized math data is pretty damn close to Hornady's data at sea level. Knowing the environmental conditions both were shot at would help.
Are AI AT-X barrels known for being 'slow' like a Tikka?

 

[TheOfficeT-Rex]

200-900 looks reasonable.
Was the old 1k and new 1k shot on the same range? How certain are you of exact yardages? If one was 10 short and the other 10 long....

Keep rocking the new 1k dope, keep a hold on the older stuff and use it as a SWAG next time you shoot shorter. I wouldn't sweat it too much. In the mean time, may be worth double checking your scope tracking just to rule that out.

 

[DocRDS]

200-900 looks reasonable.
Was the old 1k and new 1k shot on the same range? How certain are you of exact yardages? If one was 10 short and the other 10 long....

Keep rocking the new 1k dope, keep a hold on the older stuff and use it as a SWAG next time you shoot shorter. I wouldn't sweat it too much. In the mean time, may be worth double checking your scope tracking just to rule that out.

No. DIfferent ranges. The 8.5 was shot when it was high 80s, mid summer (along with 200-900). I don't have the exact env, but DA was about 2000. If I had to guess I'd actually call this one a 1K 'long' (this i'd call uncertain). I also remember some of the 400-800 were kinda odd ranges at times, so those definitly could be suspect

My "new" 1000 yard data has been shot in temps from 20 degrees to 50 degrees with DAs from roughly 0 to 1000 (multiple sessions). I feel fairly confident that this 1000 is fairly close to 1000 as they use that range for F-Class competition. (Guess I need to speed up that rangefinder aquisition too lol!)

Scope tracking was checked this summer (after my move), while it is possible it got a stiff smack here or there, its a ZCO in a Spuhr, done (remounted after tracking) in Frank's class (with fix-it sticks torque limiters), so personally I'd put it down the list after environment, shooter, barrel.

 

[DocRDS]

His weaponized math data is pretty damn close to Hornady's data at sea level. Knowing the environmental conditions both were shot at would help.
Are AI AT-X barrels known for being 'slow' like a Tikka?

Crap double--My AI barrel was faster than my Howa Barrel. But Hornady ammo is reportedly "slow". My reloads sit at 2850 for 41.5 H4350/140gr ELDM in AI, 2750 for the Howa (same charge). Once I shoot the factory stuff up, I have to re-dope for handloads. Woulda loved to do my handloads in class, but alas my workspace was MIA due to a move.

 

[6.5SH]

Crap double--My AI barrel was faster than my Howa Barrel. But Hornady ammo is reportedly "slow". My reloads sit at 2850 for 41.5 H4350/140gr ELDM in AI, 2750 for the Howa (same charge). Once I shoot the factory stuff up, I have to re-dope for handloads. Woulda loved to do my handloads in class, but alas my workspace was MIA due to a move.

I looked at 2710, what they claim for a 24" bbl.
If your new 1000 yard info is correct it's even slower for what the down range velocity is saying, given low temperatures is quite possible. But still a SWAG without exact environmental data. I don't know if Hornady still uses H4350 for that cartridge, the load data used to be printed right on the box, it no longer is.