I have a 300 yard lane at my gun club. This is the longest lane we have. With my .308 and my 6.5 Grendel, I attempt to group shots inside of a 3 inch circle. If I do my part, I can often achieve sub-moa results. This more so with the bolt-action .308 Savage Model 10.
I have zeroed the rifles with my favorite hunting rounds. I have tried to strike a good balance between terminal effects and high ballistic coefficient rounds. The results are usually predictable and consistent.
The problem came when I would switch to other rounds. I use the Hornady 4 DOF ballistic program. I used to think that if I gave it good data I would be able to hit the circle by dialing the correction into my scope. Very often, it did not work out that way. I might get close, but not what I expected.
It occurred to me that my rifles were zeroed to those specific hunting rounds. The ballistic solver assumes zero as it’s starting point I suppose. It builds an error into the numbers from the start.
My question for the group: Is there a workaround or shortcut to get around this issue? Or would I need to re-zero the scope for the new round I want to use? This is not the end of the world of course, but if there is a way to avoid re-zeroing for each round change, I would like to learn how.
It is the round that makes the shot or not. You ever heard of the definition of insanity? Doing the same thing over and over again expecting a different outcome.
Ballistics are just like that, if you use the same round and expect it to do something else you will be disappointed by the results. Changing the round changes everything. I reload my rounds for precision shooting. The brass weighs the same with the same length, same grain of bullet, (I check that) same grain of powder. If I change the bullet manufacturer I would have to go through and check the measurements and its weight because each and every adjustment means it adjusts the ballistics. Accuracy come by consistency of each round being identical.
So simply said yes, new ammo check and adjust your zero.
Every round will perform differently, unless loaded to be the exact same every round. If you change brand, or any part of the round, your impacts using the same calculations will be changed. If you are shooting for precision, you’ll have to re-zero every time you change anything.
I am probably not explaining this real well. I will preface this by letting you know that I am not handloading yet. Back to the subject.
As an example, my zero round is a 150 grain Hornaday SST. Everything is great with the numbers my ballistic calculator gives me, not counting a bit of adjustments for real velocity versus actual velocity.
When I get a new round, I will plug the performance numbers into the ballistic solver. One of them is a 168 grain SST. The solver gives me an elevation correction. I plug that into the scope and shoot. Simply put, the results were somewhat close, but not as good as expected.
I was initially puzzled as to why. Then it occurred to me that the rifle was zeroed for the 150 grain SST. Of couse the ballistic solver would assume the gun was zeroed for the 168 grain. Then the errors made sense.
My question involved any shortcuts one could use to avoid re-zeroing the rifle for the new round. I could not think of anyway to avoid re-zeroing but thought I would ask you guys. That’s it. I probably did a poor job with my description of the issue.
It makes me wonder about a sniper, as an example. If they are laying in their hide and wished, for some reason, to select a different round to shoot, would they be able to do that? Would they have the same problem or do they just dope it with firing data?
For my purposes, I now know that if I wish to change rounds, I need to re-zero. I figured as much, but wanted to ask.
You can use your 150 gr zero and the app. You’ll have to add the extra step of making the corrections to your desired outcome from the info the app gives you, then record that data and apply it to future shots. Basically you make a dope book off what the app gives you plus your corrections.
I set the zero on both at 300 yards but if you look at the both of them the arch is10 inches high on 150 and 6 niches on the 168 grain, So, the difference is four inches. if the difference is four inches then if you adjusted from that info, it would be the difference.
So, I have to ask if the difference that your calculator gives is anywhere close to that?
Ballistics calculators do not take into consideration barrel harmonics. For that you actually have to shoot the gun with the new ammo. Heavy target barrels tend to deviate less because they flex less so my precision .308 puts just about all HP 168gr match ammo close enough that for “practical” applications I can dial a few clicks when I switch from one to another and be Ok.
My light 7mm-08 sent shots 8”low and 4” left at 200 yards just from switching from a hot core 139gr SP to a ballistic tip 140gr premium ammo. But re-zeroing the gun only took 4 shots today.
The last two shots are cold bore shots. All 4 were taken using my bag as a rest at 200 yards.
This is to 2nd the idea that if you change any part of your ammo, bullet, case, primer, powder charge, the seat depth of the bullet, etc, etc. the performance of the round will be different. so if you change one factory round for another and try to simply use a calculator to figure out where the round will go, it won’t work, It might be somewhere in the ball park, but at 300 yards, your far enough out that you will see all those differences in cartridge performance start to show.
Hornady has a series of ballistics podcasts that will do much to inform you of just how much a single change of component can change things, much less switching bullets, weights, and or, ammo manufacturer.
As an example of this fact, Hornady’s 4dof calculator requires knowing a detailed, “in flight performance profile” for any bullet the program can use, this because of all those minute differences that begin to show up at range.
Beyond a certain point, either of range, or desired performance level, precision shooting rapidly becomes very complicated. When you change bullet weight you necessarily change multiple things simultaneously. A re-zero will always be required if you change from any round to any other round that is not exactly the same. Even different lots of exactly the same factory ammo can require a new zero.
Even with a ballistics calculator consistency is king. change your ammo in any way, a new zero will be required at a minimum, and likely more in most cases.
If you have the interest, go to the Hornady web site and check out their podcasts, within them is a series on ballistics from the very beginnings, all the way through the science they used to come up with their new lines of premium long range cartridges and how they did it, it’s very informative and to me, fascinating. They did a great job and it seems a lot of people really liked the series.
A friend got me into long range, its been a lot of fun to lean it. fortunately I was following a guy who had the money to try everything, and I could spend a minimum after he figured out what worked best for the money! Without that I never could have done it.