Range Report Odd DOPE results - What am I missing?

[Alex V]

Full disclaimer, I am a noob when it comes to long range shooting, I had one class out to 600 and only shot to 1K twice.

This weekend was the second time I took my 308's out to 1000 yards.

The range was Lewistown PA, 73F, 76%RH, 29.18"Hg, 1066'

Rifles used:
1. Tikka Tac A1 20" .308 Steiner Military 4-16x50 MilDot
2. LaRue OBR 18" .308 Steiner Military 5-25x56 MSR

I was using Ballistic AE to calculate drop. I started out with my Tikka Tac A1 20". The ammo was 175Gr SMK Federal Gold Metal Match.

I confirmed zero and began working my way out to 1000 yards. All the drop the App showed was spot on, all the way to 11.5Mil for 1000 yards. First round hit and a few more at 1K. All good. Then I switched to my LaRue OBR 308 and things got odd.

My OBR used to love Freedom Munitions 175gr BTHP ammo. I shot .3xx" groups with it in a class, and last year took it out to 1K at the same range. This year, I load it up to confirm zero and it is all over the place. Mil high, Mil left. The barrel had not been cleaned, only bolt wiped down but it had been maybe 60-80 rounds since last cleaning. I thought maybe it needed a cleaning. Okay, Im here, no way to clean it lets see if I can make the best of it. I load the 175gr FPGMM and it was right on target with a .5" group. Okay, maybe it doesn't like the FM ammo anymore. Lets try 500y. Ballistic AE says 3.3Mil, I dial 3.3Mil and first round hit. Three more to confirm, all hits. Okay 600 yards, app says 4.7Mil, I dial 4.7, hit. Confirm, hit. Now I say, for shits and giggles, lets try the FM again. Load it and go back to 3.3Mil for 500Y. Bullet hits high, and I think it's me, so I try two more rounds, same high impact. Okay, I measure with the reticle, and dial down to 2.6Mils - hit. Confirm with a few more rounds, all hits. At 600y it was 4Mil instead of 4.7 like the app says, and all the way out to 1K it was less than the app says. At 1K it was 11.1 instead of 11.5. I am thoroughly confused because its not even a consistent change.

I had a MagnetoSpeed with me so I tested 5 rounds of each.
FPGMM: FM:
2541 2549
2533 2555
2554 2563
2592 2556
2558 2546

The velocities are not that different to give me such a difference in drop. What could cause this? I am too much of a novice to even venture a guess.

 

[Olen_4504]

hmm strange for sure.

that FM shot well before, and it didn't this go around. maybe a funky box of ammo? you even said it was shooting all over the place.

but based on your MVs you are right, shouldn't be that big of a difference in drop. it's basically the same bullets right? same B.C.?

did you re-zero for the FM when you went back to it after trying the FPGMM?

 

[Diver160651]

2.6 @ 500 with a 175 you'd need near 2840fps.. so, MV is not the issue. Zero chance of that or having a greater than 1 G1 LOL - so it really doesn't mater how close they are in BC.

Of course, all is assuming your getting good groups and not random impacts and your bases and scope is not otherwise moving.

To me it sounds like a zero offset issue unless I misunderstood your post. If the Freedom ammo is high at 100y by 2.5" you should get that 2.6 mil number at 500, within a .1 of your number at 600. That said, if you re-zero the scope to 0-0 at 100 with the Freedom, then you need to dig deeper.

FWIW:
I've seen slightly overtightened rings to similarly weird stuff to the erector as well as by erector springs damaged by bottoming out for long periods. Next time that happens, dial back to zero shoot a field zero.. or go to the zero range. If the zero is good. Do not dial and use the reticle only, if the reticle is producing different results then your turrets. Box test your scope.

 

[Alex V]

hmm strange for sure.

that FM shot well before, and it didn't this go around. maybe a funky box of ammo? you even said it was shooting all over the place.

but based on your MVs you are right, shouldn't be that big of a difference in drop. it's basically the same bullets right? same B.C.?

did you re-zero for the FM when you went back to it after trying the FPGMM?

You may be on to something there, I did not re-zero. I went from 600y with Federal dialed back to 3.3Mil and went to 500y with FM. By the time I did that, it was a new box of FM so maybe the box I tried to confirm zero at 100 was bad. This very well could be a part of it.

I doubt FM uses SMK bullets, but they are BTHP and are claimed to have the same BC.

Also, I forgot to mention, last year at the same range, [8/26/17] the drop predicted by Ballistic AE was right on the money or pretty damn close. I used the in app feature to download local weather and wrote down all the data from that day as well. I wrote down the predicted drop, and what the bullet actually did, the only deviation was at 600 yards when the app says 4.7mil and I needed 4.5. All others were correct.

 

[Olen_4504]

probably that then. new box of ammo/not for certain if your 100-yd zero was spot on.

i did the same thing the other week. i was shooting my factory hornady stuff all day. then tried a few rounds of some handloads my buddy gave me he loaded up for that barrel. I took MVs and re-did my dope chart. wasn't on. but because I didn't re-zero the rifle for the handloads.

 

[Alex V]

2.6 @ 500 with a 175 you'd need near 2840fps.. so, MV is not the issue. Zero chance of that or having a greater than 1 G1 LOL -

Of course, all is assuming your getting good groups and not random impacts and your bases and scope is not otherwise moving.

I've seen slightly overtightened rings to similarly weird stuff to the erector as well as by erector springs damaged by bottoming out for long periods. Next time that happens, dial back to zero shoot a field zero.. or go to the zero range. Do not dial and use the reticle only. Box test your scope.

Hm.. The erector is possibly close to the bottom, the scope is in a 20moa mount and the OBR has a 20moa rail. Out of a possible 26mils I get 23 or so Mils of elevation travel.

I could understand random hits since I am a novice, but 5 for 5 at 500/600 and 700? Maybe. I went 5 for 10 at 1000. Also, I would dial to zero, then back up between every change in distance. The scope seems to track.

I doubt I would get 2840fps out of an 18" 308 gas gun, plus, I checked MV with MegnetoSpeed.

Okay, here is another curve ball, the range is uphill. How much of an affect would this have on bullet drop calculations and why would Ballistic AE be right for the Tikka and not for the OBR? I am totally lost.

 

[Alex V]

probably that then. new box of ammo/not for certain if your 100-yd zero was spot on.

i did the same thing the other week. i was shooting my factory hornady stuff all day. then tried a few rounds of some handloads my buddy gave me he loaded up for that barrel. I took MVs and re-did my dope chart. wasn't on. but because I didn't re-zero the rifle for the handloads.

Makes sense. Live and learn... and re-zero. The range has targets at 25, 50, 100, 200, 300, up to 1K. I could have easily re-zeroed the rifle without moving. Shame on me.

 

[Lowlight]

ammo is different you cannot use the same load data / ballistic solution even though they are the same weight and close in MV.

You'll be close but you'll also be off, mixing manufacturers is not recommended

 

[Alex V]

ammo is different you cannot use the same load data / ballistic solution even though they are the same weight and close in MV.

You'll be close but you'll also be off, mixing manufacturers is not recommended

Frank, what confused me is that last time, at the same range, the solver had the right answer. The bullet selected in the app was a 175gr SMK because it is the closest I could find in the drop down.

By mixing manufacturers, do you mean it will cause inconsistency or a dangerous condition for the rifle?

 

[Diver160651]

Hm.. The erector is possibly close to the bottom, the scope is in a 20moa mount and the OBR has a 20moa rail. Out of a possible 26mils I get 23 or so Mils of elevation travel.

I could understand random hits since I am a novice, but 5 for 5 at 500/600 and 700? Maybe. I went 5 for 10 at 1000. Also, I would dial to zero, then back up between every change in distance. The scope seems to track.

I doubt I would get 2840fps out of an 18" 308 gas gun, plus, I checked MV with MegnetoSpeed.

Okay, here is another curve ball, the range is uphill. How much of an affect would this have on bullet drop calculations and why would Ballistic AE be right for the Tikka and not for the OBR? I am totally lost.

I think you misunderstood my post. I was saying it was a 2.5" offset (bad zero) less than 1 mil at 100

What I was pointing out is that BC and MV are off the table, even between rounds as the cause of the 2.6 mil 500yard result if the zero was good.. NEVER look at something that can't possibly be reproduced.

BTW
I was NOT suggesting the scope but rather how to look for it in the future "if" your zero is good and you have an intermittent issue.. Such as holds a zero, dials up ok once, but doesn't return to zero, or seems to jump settings.. even when all is tight

 

[Lowlight]

it creates inconsistencies is your numbers

It's not dangerous, you cannot use 1 solution for two different loads from two different manufacturers even if they use the same bullet, doesn't really work that way. The rifle will know the difference, make two tracks in your software, one for one bullet and one for the other

 

[Alex V]

I think you misunderstood my post. I was saying it was a 2.5" offset (bad zero) less than 1 mil at 100

What I was pointing out is that BC and MV are off the table, even between rounds as the cause of the 2.6 mil 500yard result if the zero was good.. NEVER look at something that can't possibly be reproduced.

BTW
I was NOT suggesting the scope but rather how to look for it in the future "if" your zero is good and you have an intermittent issue.. Such as holds a zero, dials up ok once, but doesn't return to zero, or seems to jump settings.. even when all is tight

Gotcha! Yes, I misunderstood. Thank you!

it creates inconsistencies is your numbers

It's not dangerous, you cannot use 1 solution for two different loads from two different manufacturers even if they use the same bullet, doesn't really work that way. The rifle will know the difference, make two tracks in your software, one for one bullet and one for the other

Understood! Thank you sir. Again, still learning and appreciate all the help.

 

[Diver160651]

make two tracks in your software, one for one bullet and one for the other

^I am sure this made sense, but just incase:

Specifically for this example, you'd enter that 2.5" offset or whatever it is, into your "Zero Height" in AE for the Freedom and NOT slip your turrets, if the primary ammo was the FGMM and actually zero'd for it with the 0-0 turret setting. Then change MV and BC if it really is different.

AE and AB calls the POI, left to or right at your zero, "Zero Offset". You'd want to enter that number as well. Some programs ask for a "vertical offset" number as well as a "windage offset" number. Other programs ask for "zero height" and zero windage" It is kinda weird, you'd think it would be consistent.

For clarity, I however, also refer to any POI that is a shift from your expected POI caused by positions or shooters as an offset.

 

[Alex V]

^I am sure this made sense, but just incase:

Specifically for this example, you'd enter that 2.5" offset or whatever it is, into your "Zero Height" in AE for the Freedom and NOT slip your turrets, if the primary ammo was the FGMM and actually zero'd for it with the 0-0 turret setting. Then change MV and BC if it really is different.

AE and AB calls the POI, left to or right at your zero, "Zero Offset". You'd want to enter that number as well. Some programs ask for a "vertical offset" number as well as a "windage offset" number. Other programs ask for "zero height" and zero windage" It is kinda weird, you'd think it would be consistent.

For clarity, I however, also refer to any POI that is a shift from your expected POI caused by positions or shooters as an offset.

Makes sense. The rifle was zero's for Freedom Munitions 175gr, not the FFPGMM.

The moral of the story is I need more trigger time and more time with the Ballistic AE.

 

[Olen_4504]

Makes sense. The rifle was zero's for Freedom Munitions 175gr, not the FFPGMM.

The moral of the story is I need more trigger time and more time with the Ballistic AE.

wait what?

my theory was you shot with the FPGMM and said it was 'right on target' i thought you meant dead zero and then you shot to distance and nailed it every time. then you went back to the FM and were shooting high every time.

my theory was your rifle was zero'd for the FPGMM and not the FM which is why your dope wasn't working out for the FM.

 

[Olen_4504]

honestly, it doesn't really matter. no need to confuse you or me further lol.

fact is what Frank said - you just can't mix and match brands and expect same results. have treat each one individually. meaning zero, and separate data and drop charts.

 

[Alex V]

wait what?

my theory was you shot with the FPGMM and said it was 'right on target' i thought you meant dead zero and then you shot to distance and nailed it every time. then you went back to the FM and were shooting high every time.

my theory was your rifle was zero'd for the FPGMM and not the FM which is why your dope wasn't working out for the FM.

LOL Yes it is all getting confusing. The first half of your theory is correct.

OBR was zeroed with FM in NJ at slightly above sea level. This range is in PA at roughly 1000' so I wanted to check/confirm zero. Group was all over the place. Tried FGMM and the group was .5" with POA = POI. When shooting at distance FGMM agreed with Ballistic AE, Freedom Munitions was high despite having very similar MV and bullet weight was 175gr for both. I never rechecked zero with FM and used a different box when shooting at distance than when I first tried to check zero, so it could have been a bad box.

At my local range my 100y groups are nearly identical with FM and FGMM with very little POI shift. When the ammo was purchase, FM was much cheaper than FGMM so I decided to use it, seeing the results were not too dissimilar. My local range, however, is only 200y so it wasn't a comprehensive test by any means. This is also why I ASSumed I can use the same solution from Ballistic AE for both.

The one thing I learned is to write it all down, which I am doing.

 

[Squat]

Did you overheat your barrel? That will cause what you are talking about.

 

[Alex V]

Did you overheat your barrel? That will cause what you are talking about.

Cadence of fire was fairly slow. Maybe 1 round every 10 to 15 seconds for about 5 rounds. Then reference the app, dial, repeat. I don't think that would overheat the barrel. Would it? Total of maybe 30 rounds tops by the time I got out to 1K

 

[Squat]

depending on the rifle and barrel yeah. I have seen it on hot days it heats up fast. If you are burning your hands and running a stock barrel it coudl do that for the last 5-10 shots.