Odd ballistic data M80

[PBWalsh]

Hi,

So I doped my 16” large frame 308 gasser today at 310, 390, 436, and 517 yards. Lets call it 300, 400, 430, and 520. All data in mils and suppressed.

Data for IMI 175 OTM:
300 - 1.3
400 - 2.0
430 - 2.3
520 - 3.3

These figures seem to line up very well at 2600fps on JBM. However, the next batch is whats weird.

Data for S&B/ZSR M80 ball:
300 - 1.4
400 - 1.9
430 - 2.2
520 - 2.7

I tried truing this in Ballistics AE at 517 yards. If I use that velocity given, nothing else lines up, and vice versa.

As a note, my 20” bolt rifle velocity with a 175 (2504fps) matches its data well +/-.1-.2 mil. I am only having an issue with my M80 data set. Another note, when my 16” barrel heated up a bit, I noticed the data change to:

300 - 1.0
400 - 1.7
430 - 2.0
520 - 2.5

This data held a bit more consistent over the remaining rounds I fired for the day of M80 loads. I did not test the IMI 175 under heat.

Does anyone have a guess as to whats going on? Could it be an SD error in bulk M80 loadings? I did notice some random flyers with the ZSR load splashing 1-2 mils off target.

Thanks in advance,
PBWalsh

 

[BCP]

What are the velocities from your 16.

 

[PBWalsh]

What are the velocities from your 16.

Unknown. I only have hard DOPE to guess velocities as I do not have a chronograph.

 

[hlee]

Have you done a tall target test on the scope?

Maybe the bc in your calculation is wrong.

What was the wind doing? That can have an effect on your vertical.

Did your targets have a ‘water line?’ The ‘Any hit is a good hit’ mentality doesn’t apply when doping a rifle.

With no velocity info, you have a lot of variables to play with…

 

[PBWalsh]

Have you done a tall target test on the scope?

Maybe the bc in your calculation is wrong.

What was the wind doing? That can have an effect on your vertical.

Did your targets have a ‘water line?’ The ‘Any hit is a good hit’ mentality doesn’t apply when doping a rifle.

With no velocity info, you have a lot of variables to play with…

Have not done a tall target. However, my IMI M118LR data lines up +/-.1 mil. And I went up and down the turret, used holds, etc. to confirm dialed DOPE. If I did miss and see splash, I dialed what I saw and earned a hit. I’d wager any non-center hit was due to my fundamentals not being 100% behind a large gasser.

0-3 mph wind, mostly 0 as it was a dead day.

Did not do a water line as the steel was fresh and I could see where my impacts landed.

I’ve got a DMR competition on the 26th at that range, so we’ll see.

 

[GreenGO Juan]

Did you rezero the rifle when changing ammo?

 

[PBWalsh]

Did you rezero the rifle when changing ammo?

My M80 zero is .5 mil right 0 mil up/down. compared to M118LR. I adjusted windage and went from there.

 

[RegionRat]

If you have this ZSR ammo, I would use caution and put it aside till they get to the bottom of their investigations. YMMV

 

[PBWalsh]

Well, thats my lot as well.