Would you bother to re-zero? (ammo change)

[Annapolis]

Also there's alot of anecdotal data(and possibly some empirical data) that says you need to clean the barrel to steel to get good groups when switching from lead core to monolithic copper.

That’s interesting. I think I’ll see how it does first…

 

[Castle Rock]

There is a lot of info here that is true but not really important here, the 350 is a 150 yard gun and if zero is off by two inches or it groups 3 inches that won’t make any real difference

 

[Annapolis]

I did wonder about that key detail. My takeaway from all this, though, is that I should re-zero---with the logic of I can't possibly regret doing so, but could definitely regret not.

A couple gallons of gas is a small price to pay, and it's always fun to get to the range.

At the moment, I have only one box of the monometal ammo; I'm hoping that's more than enough for both the sighting and the (one tag) hunt.

Really wish there were a closer place to sight in, but all the nearer ones are membership-based clubs with elaborate joining procedures that require you to know someone (I don't) or attend events to make contacts, but those are always at times that'll never mesh with my work schedule. They're clearly not looking for casual folks like me who'd just come four or five times a year--though I'd gladly pay the full dues to save the pain of driving out the eastern shore. Ah well. Worse problems one could have.

 

[bnewt3]

There is a lot of info here that is true but not really important here, the 350 is a 150 yard gun and if zero is off by two inches or it groups 3 inches that won’t make any real difference

There's a philosophical point in there though. And that is that we are responsible for knowing exactly where every bullet we shoot is going to go.

 

[Macintosh]

There is a lot of info here that is true but not really important here, the 350 is a 150 yard gun and if zero is off by two inches or it groups 3 inches that won’t make any real difference

I don’t think I agree with this. I understand where you’re coming from and in most cases it’s certainly true. But, if you’ve got a gun that shoots 3 inch groups—tons of guns for straightwall cartridges do—and you change ammunition and the point of impact changes by 3 inches, you’re going to have some percentage of those shots that are 4 1/2 inches away from your point of aim. That’s barely on a 9” plate by the skin of your teeth, before you even add in ANY shooter error. When you stack that on top of an insecure shooting position, that easily puts some of your shots off a vital size target even at 100 yards. Even with the example given (2” poi shift with 3” groups), it only takes a small amount of wobble to put some shots off a 10” target. Because of this I just don’t think it’s anything but a mistake to not re-zero when you change ammo. The zero is by far the easiest to control part of making a good hit, so we ought to make it a priority.

 

[EdP]

I'm hoping the OP lets us know what happens after he gets to the range.

 

[tntrker]

Why would you not? I mean any change can affect your shooting. Besides, go shoot anyhow...You should be shooting anyhow even when nothing changes..

 

[Hnthrdr]

At first I was like, absolutely check zero… but after reading the rest of your situation, you could get away with not doing it… but best to check zero if possible, 150 yard shot you will likely be minute of deer but it’s always best to know

 

[hibernation]

Get three boxes of the new ammo and check your zero with a good sized group (10 shots). Make the required adjustments off that group. Then confirm it with another 10-shot group.

Is that really necessary for 150 yards though? I've kept casual track of my own zeroing process, how close I would be to my final adjustment at each shot. 3 rounds could be a few clicks off pretty easily, but once I hit 5 I'm usually within 1 or 2 clicks of the 10-round zero.

Put another way: if he ends up with a 2" group for 10+ rounds, the worst possible zero he could get by stopping early is 1" away from center. For 100yd woods shooting, a 5 round zero seems pretty reasonable. Diminishing returns after that point IMO. The extra rounds might be better spent shooting positionally, see if he can keep it on target how he actually hunts.

 

[Weldor]

Let us know how it goes. I'd be curious to see without cleaning a group of Winchester xp against the mono's.

 

[TheGDog]

Just go find a ballistics calculator program you like, for this purpose you could just try like Nikon's Spot-on online app. Plug in the ballistic coeffecient and muzzle velocity, and it can help you make field charts, tell you where the impact point needs to be on the Target if it's less than your target distance that you're zero-ing for, etc.

With this tool, you should be able to figure out if your current zero is reasonably close to what you've already got it set as.

Like if the Muzzle velocity is similar and the Ballistics Coefficient number is very close, probably wouldn't much matter.

I'd run thru this tool for your current load, observe where the point of impact is supposed to be on a 25yd target for an XXX yard zero.

Then run it for the new ammo, and check where THAT 25yd point of impact is when set to same Target zero distance.

But it IS BEST... to re-sight-in with the new ammo.

 

[Q_Sertorius]

Is that really necessary for 150 yards though? I've kept casual track of my own zeroing process, how close I would be to my final adjustment at each shot. 3 rounds could be a few clicks off pretty easily, but once I hit 5 I'm usually within 1 or 2 clicks of the 10-round zero.

Put another way: if he ends up with a 2" group for 10+ rounds, the worst possible zero he could get by stopping early is 1" away from center. For 100yd woods shooting, a 5 round zero seems pretty reasonable. Diminishing returns after that point IMO. The extra rounds might be better spent shooting positionally, see if he can keep it on target how he actually hunts.

So, if his rifle is shooting 2 MOA groups, then the best he can expect is to put all his rounds into a 3” circle at 150 yards. But if his zero is off by an inch, that adds to his potential error (i.e., even with a perfect shot, he could be off by another 1.5” at 150 yards). Which, on a stereotypical whitetail vital zone of an 8” circle, gives him a 3.5” margin of error for hitting in the vitals at 150 yards. That’s a pretty thin margin as far as I am concerned - especially under field conditions. No way I would want that added - easily avoidable - error for an offhand or even sitting-unsupported shot at 150 yards on a live animal. An offhand shot is usually regarded as a 6-8 MOA shot. A sitting-unsupported shot is usually a 4 MOA shot. So, getting the avoidable error down to a reasonable level makes a big difference.

Take the time to get a good zero the first time, eliminate the built in error to the largest extent practicable, and then practice shooting from field positions. Whatever range you can hit 10/10 in the vitals is your maximum range from that position.

 

[Annapolis]

I'm hoping the OP lets us know what happens after he gets to the range.

Will do!

 

[TheGDog]

Big thing I'd say to yourself? How pissed would you be if you ended up loosing an opportunity, all because you didn't re-sight-in to doubly-confirm you're GTG.

If you miss an opportunity because you aren't totally GTG with the things that ARE under YOUR control... think about how damn pissed you'd be at yourself.

 

[Annapolis]

That is where I landed after about the third reply. But I appreciate all of them!

 

[hibernation]

So, if his rifle is shooting 2 MOA groups, then the best he can expect is to put all his rounds into a 3” circle at 150 yards. But if his zero is off by an inch, that adds to his potential error (i.e., even with a perfect shot, he could be off by another 1.5” at 150 yards). Which, on a stereotypical whitetail vital zone of an 8” circle, gives him a 3.5” margin of error for hitting in the vitals at 150 yards. That’s a pretty thin margin as far as I am concerned - especially under field conditions. No way I would want that added - easily avoidable - error for an offhand or even sitting-unsupported shot at 150 yards on a live animal. An offhand shot is usually regarded as a 6-8 MOA shot. A sitting-unsupported shot is usually a 4 MOA shot. So, getting the avoidable error down to a reasonable level makes a big difference.

Take the time to get a good zero the first time, eliminate the built in error to the largest extent practicable, and then practice shooting from field positions. Whatever range you can hit 10/10 in the vitals is your maximum range from that position.

Totally fair answer, and it's never a bad idea to shoot more and be confident in your setup.

 

[Macintosh]

Sounds like op is set. Just because I think theres some misinformation here for posterity:

The ballistics you get from an app have functionally NOTHING to do with your zero—the app always assumes your poi is exactly on top of your poa unless you give it an offset measurement—but the app does not predict zeros, it just doesnt work that way. All of your known variables can be the same, and the different burn between even production-lots of the SAME ammo (remember we cant check that in this case) can make a couple-moa difference in zero. BC and box velocity is meaningless in this situation. Some “similar” ammo or even different lots of the “same” ammo will be very close at 100 yards—but lots wont. The only way to predict it is to test it.

 

[flyfisher117]

There is not a good reason not to go check zero. All copper projectiles can fly different. My .30-06 saw a 6-7” POI shift shooting TTSX compared to my old Partitions, at 100 yards. Even if that’s still in the vitals it’s not OK and should not be accepted as close enough.