Ballisticians - What went wrong with my sight in of a .375HH?

[rookhawk]

Trying to figure out my experiences at the range yesterday.

.375 H&H
Federal 300gr Factory Loads (A-frame and woodleigh hydrostatic)
25" barrel
1.6" scope height

I reviewed the Federal website and they stated that a 100 yard zero would yield a 50 yard impact about 0.10" high. Both cartridge loadings.

I zeroed at 50 to start and had good groups. Also good groups at 100.

The confusion I need to understand in my own mind:

With a good 50 yard sight in I went to 100 yards and I was about 4" high. Why would it be so much of a deviation from published specs? I acknowledge perhaps lower velocity from a 25" barrel than whatever barrel they tested with (26-28") but it still seemed a bit less flat shooting than I anticipated.

No chrony so I don't have those key measurements to assist. I'd just like some learned speculation as to why my experiences deviated so much from published drop charts.

The good news is that the rifle was plenty accurate and really mild recoiling. I was shocked that its recoil was so much less than my loathed 300HH. (9lb 375 vs 7lb 300...go with the 375!)

Thoughts?

 

[rookhawk]

Published drop chart: https://federalpremium.com/products/details/rifle.aspx?id=870

 

[stug]

I wouldn't worry about it being higher at 100yd. Adjust the scope for the height you want at 100yd then go back to 50yd and see where it is printing.
Then go and see where it is hitting at 200yds and you'll be good to go.

 

[sestoppelman]

The difference between outside and inside, how the rifle was held during testing, (hand held or machine, recoil rise) temperature, elevation, slight difference in barrel length changing velocity. A lot of things can influence this. I would have been a little surprised at that difference too, but I wouldn't let it concern me. As above sight it in and take notes. I use the ballistic tables in the back of loading manuals and they often don't quite jibe with my range results. For instance I like to use a 200 yd zero at least until some outfitter says no. I run into the same thing you are talking about and often end up landing higher on the target at 200 than expected using the tables for heights at 100 to start, then go back and adjust scope until on at 200, see where I am at 100 and sometimes go somewhere in between so I am close to both. For an exact science it often isn't.

 

[BRICKBURN]

Too many variables for me to guess at a reason.
I always blame the rifle. It is never true but it makes me feel better to operate in denial.

 

[rookhawk]

Thanks @BRICKBURN you always know what to say to make me feel like I'm an okay shot!

 

[DM Shooting]

Lots of good reasons above for why it happens but to me I don't care what a piece of paper or app say.

I zero at 100 normally 1-1.5" high, I'll make not of the poi at 50, 150 and 200.

That what the round does in my rifle not someone else's so it the only results in really interested in

 

[colorado]

I wouldn't worry about it being higher at 100yd. Adjust the scope for the height you want at 100yd then go back to 50yd and see where it is printing.
Then go and see where it is hitting at 200yds and you'll be good to go.

Agree. If it's a new rifle or scope, I sight in dead on a 25 yards, then adjust it so it's 2.5" high at 100 yards and shooting good (sub MOA) groups, then check where it's printing at 50 yards and 200 yards. Ballistic tables are almost always correct, math doesn't lie. I do this with our 30-30, 270s, and big bores (375, 416 and 500).

 

[sestoppelman]

Ballistic tables should be correct and yes, math doesn't lie, but they are done by computer I suspect as opposed to a shooter using a real rifle from a bench. I think this probably more accounts for the variances we find as actual shooters trying to compare to ballistic tables. With a ballistic coefficient for the bullet and a known velocity, the computer does the rest for as far as the eye can see. It doesn't take into account the human element.

 

[ChrisG]

Is it a new rifle and a new scope? When I first put mine on paper on kept having a wandering zero for the first 15 rounds. I couldn't figure it out until I relized that the scope was inching forward under recoil. I went home and tighted down the screws a bit more and never had the problem again. I would advise you to check your scope rings and make sure the scope isn't slowly shifting forward.

 

[Scott Slough]

The confusion I need to understand in my own mind:

With a good 50 yard sight in I went to 100 yards and I was about 4" high. Why would it be so much of a deviation from published specs? I acknowledge perhaps lower velocity from a 25" barrel than whatever barrel they tested with (26-28") but it still seemed a bit less flat shooting than I anticipated.

...

Thoughts?

My thought is ... Rifles can't read ballistics charts !

 

[sheephunterab]

4" rise from 50-100 yards????? Something isn't right here. Is this a consistent problem or did you just see it once? What happens if you zero at 100...where are you hitting at 50 then? This has nothing to do with ballistics me thinks...... What power scope are you using? What type of target are you using? Are you using same rest for both? I'd zero at 100 and reevaluate.

 

[PHOENIX PHIL]

Numbers don't lie, but they sometimes don't tell the full story. Ballistics are affected by more than just muzzle velocity, ballistic coefficient and the effect of gravity. There are other variables. If I were developing a ballistics table, with those variables being unknown, I would not consider them in the calculations. The tables should just be used as a reference for overall expected behavior and not necessarily what will exactly happen.

I can't help but wonder if the shooting setup is coming into play here.

For example, I took my wife to the range yesterday to start getting her shooting more and preparing for a future hunt. She never hunted previously until 2010 when I was the hunter for my first safari. She shot an impala with a .223 and was bitten hard by the bug. So off we go yesterday with the .308 Win loaded up similarly for when I took my then 15 year old to Africa. I shot first to ensure the sight in was still the same and it was, 2" high at 100 yards and right down the middle. She then took over and was 4" high and a bit right with tight groups. Later in the shoot, I shot again and was still shooting 2" lower and a touch left of her groups. So what changed?

Well obviously the shooter changed, but what really was the difference? I don't know for sure, but her physical build, how she holds the rifle, where the rifle rested on the bags for her to be comfortable and who knows what else come into play.

I would set the scope for where you want the bullet to print at 100 yards and then shoot closer/further to characterize YOUR rifle for when YOU shoot it.

 

[sheephunterab]

Sure there's room for variance in ballistics due to a number of factors but not 4" between 50 and 100 yards.....maybe between 400 and 500 yards but not 50 and 100. Rather than using published tables there are many ballistic programs that allow you to plug all the variables in for much more reliable results but they are only as accurate as the data that's input and very few shooters own even the basics like a chrony. For long range shooters they are a must but not for 50-100 yards!

 

[PHOENIX PHIL]

Sure there's room for variance in ballistics due to a number of factors but not 4" between 50 and 100 yards.....maybe between 400 and 500 yards but not 50 and 100. Rather than using published tables there are many ballistic programs that allow you to plug all the variables in for much more reliable results but they are only as accurate as the data that's input and very few shooters own even the basics like a chrony. For long range shooters they are a must but not for 50-100 yards!

Agreed that it's extreme, but I have seen some strange behavior that I can't explain either. First example that comes to mind is my .458B&M shooting 260gr CEB SOCOM's. As you can imagine in that light of a bullet for that caliber, the BC is not good at all. After hmming and hahhing over ballistics tables, I decided to sight in the scope at 2" high at 100 yards. I expected this to put the bullet right at 0" at 200 yards. When I shot that range the POI barely dropped, at 1.75" high and with a tight group. After seeing that, I rethought about the holdover at 300 yards and of course figured it would be much less to hit the target. Wrong, it was about the same to a bit more than I'd figured.

 

[sheephunterab]

The additional speed of a lighter bullet trumps BC for quite a few yards out...often well beyond practical shooting ranges.

 

[PHOENIX PHIL]

The additional speed of a lighter bullet trumps BC for quite a few yards out...often well beyond practical shooting ranges.

That may very well explain that situation. I'd still say it would be wise for rook to sight in where he wants to be at 100 yards and then characterize at 50 and 200. I wouldn't be surprised if the delta between 50/100 reduces from the 4" he's seeing now.

 

[sheephunterab]

That may very well explain that situation. I'd still say it would be wise for rook to sight in where he wants to be at 100 yards and then characterize at 50 and 200. I wouldn't be surprised if the delta between 50/100 reduces from the 4" he's seeing now.

Agree 100%. If the 4" variance doesn't change, however, I'd want to know why because it definitely isn't ballistics!