6.5 Creedmoor ballistic anomalies

[uhuru]

I have had built a 6.5 Creedmoor built for me by a good friend and awesome gunsmith, Mike Norris. He used Fully trued Remington action and fitted 25 inch 1:8 International Barrels inc 5 r barrel . This was cnc profiled in house from a parallel blank to a heavy palma contour. The muzzle was screw cut M18x1.0 metric and wears one of our Vortex muzzle brakes . A tactical bolt handle was fitted and the trigger was tuned to give a clean crisp break at 2.5 lbs . The barrel was bead blasted to a satin glass bead finish . The stock is a McMillan A5 into which we inlet a Tier one Aics bottom metal and then the barrelled action was fully pillar bedded .

So that’s the rifle.

The testing range: is 1,400 above sea level and in the UK. Wind on the test day was a full right to left 30MPH.

4 sets of differing ammo nature.

• Sako 144g Range ammo 2690 fps
• Barnes 140g precision match
• Hornady 129g sst 2960fps
• S&B 140g tactical ammo 2660 fps

Each ammo nature (maybe not the S&B) was effectively a same hole group at 100 yards. I was and still am delighted by the way the rifle shoots. The conundrum or anomaly however is when I reach out to the 200 yards…..i am exactly 1,2Mrads low. WTF? This was measured by tape measure and also off the reticles too.

I confirmed this drop at a sniper fig11 at 200 yards having once reset my scope to my 100 yard zero. Tested the zero and was still spot on. So out to 200 yards without changing my scope, held what I would have expected to be the holdover of an absolute max of 4” and fired. Yep, I was another 4” low, giving a total of 8” low from my POA. Tried time again and this same point was proven, from POA to POI was 8 fecking inches.……

The frustration really ends at the 200 yard mark I suppose, because I then went from there to 800 yards having stopped at 300 and 400 yards firstly and those corrections were spot on. I was hitting the 10” and 6” plate all day long…..

I am using a PM11 scope FFP Mil Mil – same as on my old military rifles and now on my civvy stuff too. I also swapped the scope, and this had no effect on my findings. therefore I ruled out a scope issue.

I am using Tier one rings and a 20MOA tier one rail. (fitted correctly).


So that this does not become a huge note my drops for the Sako and the Barnes, where:

100yard zero

200yards - 1.2 mrad come up from zero

300 yards – 1.6 mrad come up from zero

400 yards – 2.2 mrad come up from zero

800 yards – 7.0 mrad come up from zero

If anyone has any ideas I would love to hear them as to why such a big differential at 200 yards. . Many thanks. Tim

 

[308pirate]

Are you puzzled because the actual bullet's flight path isn't exactly what the ballistic models predict?

If I were you I would write down what actually happened on target on a notebook, make that your dope and move on without another thought to it.

 

[morganlamprecht]

theres too much error in all of this for anyone to really answer...

1.2 @ 200 is way off typical
1.6 @ 300 is way off typical
2.2 @ 400 is off...
7 @ 800 could be right, but based on your other values, its out of whack also

either you have some strange environmental effects going on, or something from your inputs is way off for a 6.5, 140, going ~2700 fps to match any of that in a ballistic calc

for truing dope, you have to be precise...cant be .1-.2 off at zero range unless accounted for in the calc...hitting 6" and 10" plates at 3 and 400 also has a ton of error unless youre positive youre hitting dead center

the elevation above sea level alone doesnt tell the whole story for the calc either...needs the rest of the data, but that wouldnt matter a ton at 3-400 yds anyways

theres a lot of error in all this...and for truing ballistics, you need to be spot on with everything...with all the inputs correct, a good ballistic calc should be really close inside 800 yds and only need small tweaks past that even until you get out past 1200 or so

 

[uhuru]

Are you puzzled because the actual bullet's flight path isn't exactly what the ballistic models predict?

If I were you I would write down what actually happened on target on a notebook, make that your dope and move on without another thought to it.

I am minded to do just that, it is that in 45 years of shooting I have not come across this anomaly before and was wondering if anybody could explain such a drop. I do take your point. thanks.

 

[uhuru]

theres too much error in all of this for anyone to really answer...

1.2 @ 200 is way off typical
1.6 @ 300 is way off typical
2.2 @ 400 is off...
7 @ 800 could be right, but based on your other values, its out of whack also

either you have some strange environmental effects going on, or something from your inputs is way off for a 6.5, 140, going ~2700 fps to match any of that in a ballistic calc

for truing dope, you have to be precise...cant be .1-.2 off at zero range unless accounted for in the calc...hitting 6" and 10" plates at 3 and 400 also has a ton of error unless youre positive youre hitting dead center

the elevation above sea level alone doesnt tell the whole story for the calc either...needs the rest of the data, but that wouldnt matter a ton at 3-400 yds anyways

theres a lot of error in all this...and for truing ballistics, you need to be spot on with everything...with all the inputs correct, a good ballistic calc should be really close inside 800 yds and only need small tweaks past that even until you get out past 1200 or so

I am 100% in agreement with you. the range has its own unique qualities as it is in a Vally and wind values do some horrendous things, even with the 338lm. my only real concern is why the so much of a drop at 200 yards? I don't get it?

 

[308pirate]

I am minded to do just that, it is that in 45 years of shooting I have not come across this anomaly before and was wondering if anybody could explain such a drop. I do take your point. thanks.

I get it. As an engineer it isn't in my nature to just ignore cause and effect, but sometimes the juice isn't worth the squeeze.

 

[morganlamprecht]

I am 100% in agreement with you. the range has its own unique qualities as it is in a Vally and wind values do some horrendous things, even with the 338lm. my only real concern is why the so much of a drop at 200 yards? I don't get it?

id take note and then try to verify another time or another range...ive seen some weird shifts on certain days/conditions that go away the next day...never that much at 200 yds, but .2-.4 from 400-800 isnt unheard of

 

[isofahunter]

Believe the Bullet.

 

[lash]

I thought a bit about your issue and thinking just outside the box I put together this info.

trajectory calcs using 0 yards as zero:

Note the between 100y and 200y, there is roughly an 8” drop.

Now look at trajectory calcs using 100y zero:

This doesn’t explain anything really. Unless of course your zero stop wasn’t really set at 100y for this round.

Trying to understand this using conventional ballistics logic doesn’t work at all, so I am offering another view. Think about it for a while.

 

[Tokay444]

Where did you derive those velocities?

 

[uhuru]

I thought a bit about your issue and thinking just outside the box I put together this info.

trajectory calcs using 0 yards as zero:

View attachment 7280552
Note the between 100y and 200y, there is roughly an 8” drop.

Now look at trajectory calcs using 100y zero:

View attachment 7280556
This doesn’t explain anything really. Unless of course your zero stop wasn’t really set at 100y for this round.

Trying to understand this using conventional ballistics logic doesn’t work at all, so I am offering another view. Think about it for a while.

thank you for your thoughts. appreciated.

 

[uhuru]

id take note and then try to verify another time or another range...ive seen some weird shifts on certain days/conditions that go away the next day...never that much at 200 yds, but .2-.4 from 400-800 isnt unheard of

appreciate you taking the time. thanks you.

 

[Steel head]

id take note and then try to verify another time or another range...ive seen some weird shifts on certain days/conditions that go away the next day...never that much at 200 yds, but .2-.4 from 400-800 isnt unheard of

Those are some wonky numbers but I’ve also had days that stuff was just weird.
Definitely note the conditions and drops and see if they work out again.
Also check your zero.


Here’s my 260 for comparison with a 140 BTHP at 2750ish.

I’ve ran this load for a lot of years in a lot of conditions.

 

[uhuru]

Those are some wonky numbers but I’ve also had days that stuff was just weird.
Definitely note the conditions and drops and see if they work out again.
Also check your zero.


Here’s my 260 for comparison with a 140 BTHP at 2750ish.

I’ve ran this load for a lot of years in a lot of conditions.
View attachment 7280804

very kind of you - thank you for your response. I appreciate it.

 

[Jack Master]

I have a couple questions.
1. When did you zero the rifle? Was it that day in 30mph winds or was is a few day prior in zero wind?
2. Just asking to make sure you are positive; Was the wind right to left?

If you have a 30 mph wind you will experience aerodynamic jump. If you zeroed your rifle in 30mph R to L wind your bullet should impact will be about a 1/2 mil high at 100yds. (Hornady 4Dof for Hornady 140BTPH at 2650fps) If you dialed this 1/2 mil out of your rifle to get a perfect zero in 30mph winds you started with your rifle 1/2 mil low. (-1.8" at 100yds)

If you zeroed your rifle in no wind then took it out in 30 mph R-L wind your would have a zero dial to 200yards because of this Aero Jump. All your impacts would be higher then you think they should be but your situation is the opposite. This is why I am asking if the wind was for sure Right to Left. If the wind was actually L to R you will have 3-4 tenths of additional drop than you thought and your data might start to line up.

Rifle zeroed in no wind condition - then shoot with 30mph L to R
200yds = 1.5 mil
300yds = 2.2 mil
400yds = 3.0 mil
800yds = 7.4 mil
(Hornady 4Dof for Hornady 140BTHP at 2650fps)
These are close to you numbers.

IN the end we need to believe the bullet, but you may also want to double check your zero and this data on a more calm day.

 

[uhuru]

I have a couple questions.
1. When did you zero the rifle? Was it that day in 30mph winds or was is a few day prior in zero wind?
2. Just asking to make sure you are positive; Was the wind right to left?

If you have a 30 mph wind you will experience aerodynamic jump. If you zeroed your rifle in 30mph R to L wind your bullet should impact will be about a 1/2 mil high at 100yds. (Hornady 4Dof for Hornady 140BTPH at 2650fps) If you dialed this 1/2 mil out of your rifle to get a perfect zero in 30mph winds you started with your rifle 1/2 mil low. (-1.8" at 100yds)

If you zeroed your rifle in no wind then took it out in 30 mph R-L wind your would have a zero dial to 200yards because of this Aero Jump. All your impacts would be higher then you think they should be but your situation is the opposite. This is why I am asking if the wind was for sure Right to Left. If the wind was actually L to R you will have 3-4 tenths of additional drop than you thought and your data might start to line up.

Rifle zeroed in no wind condition - then shoot with 30mph L to R
200yds = 1.5 mil
300yds = 2.2 mil
400yds = 3.0 mil
800yds = 7.4 mil
(Hornady 4Dof for Hornady 140BTHP at 2650fps)
These are close to you numbers.

IN the end we need to believe the bullet, but you may also want to double check your zero and this data on a more calm day.

you are a gentleman. thank you. the range we have is set in 5,500 acres of mountainous terrain. the wind is a real killer here and the sniper platforms really do earn there keep. I take note of your comments and will revisit the test in a tunnel range and revert back to you. yes the wind was a r to l and the rifle was zeroed on the day. your answer is very comprehensive and I appreciate you taking the time. thank you.