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

[Annapolis]

Hi all,

I'm in a straight-wall state (MD), so am using 350 Legend, which I like a lot for what it does. I'm a factory ammo guy, not a re-loader, so both of the examples I'm about to point to are off-the-rack cartridges.

My go-to has been the Winchester "Deer Season XP" 150gr. That's what I'm zeroed for right now. It's a lead-core bullet design.

In a few weeks I'll be participating in a mentored hunt that requires the use of all-copper bullets. It's probably the incentive I need just to make this switch anyway.

I went ahead and bought a box of Winchester "Copper Impact"---they're also 150gr, but are monometal copper with a polymer tip.

Ballistically, I think they're really similar, but I'm a little confused by the charts Winchester has on their site (attached): if I'm following (and I'm relatively new to ballistics and not great at math-ing, so bear with me), it looks like they've calculated the "Deer Season" load using a 150yd zero, and the "Copper Impact" load using a (I think more typical?) 100yd zero. I don't get why they would do this for two same-caliber, equal-weight bullets, as it makes it kinda hard to compare them apples-to-apples. I'm guessing my zero will be just fine, but am wondering what others think. To explain, for me to dial in my rifle (again) requires 3 hours of roundtrip driving, as there's no public outdoor range near me, so it's not a casual thing i just do for no good reason. But, of course, if there's a real chance my zero will be significantly off with this change, that is a good reason.

TIA

 

[Annapolis]

I should add: would not be shooting past 150yds with a 350 Legend. The areas I hunt---that wouldn't really happen anyway, as it's all forested.

 

[Annapolis]

And now I just discovered the Ballistics Calculator/comparison tool on Winchester's site---that's immensely helpful.

Using that, here's what I see: with a 100yd zero, the "Deer Season" drops 7.5" at 200yds; the "Copper Impact" drops 8.1" at the same distance.

So... a 0.6" difference at 200yds. At 150yds, the difference is between 2.4" and 2.6".

That doesn't seem worth re-zeroing to me, but now that I've responded to my own thread twice, I'm open to other ideas if anyone wants to share. (Maybe I've answered my own question.)

 

[Nickziegler]

Re check your zero. I shoot factory and will re check zero on the same ammo from different lot # just to make 100% sure

Sent from my SM-S918U using Tapatalk

 

[ckleeves]

Check your zero. You can have two different bullets started at the same velocity with the same weight and BC but that doesn’t mean that they share a zero.

 

[Annapolis]

This is good for me to hear.

 

[Colorado Cowboy]

If you can get the BC of both bullets, compare them. The closer they are to each other , the better.

My belief is that every rifle is different because of manufacturing tolerances...ammo is the same situation. I would reshoot with the new ammunition.

 

[The Harbor Master]

I would check it... It depends on your definition of "significantly," but the same bullet weight with different bullet shape/density/BC = different POI. It may not be *much* different, but I'm way too obsessive and particular to just hunt with it hoping it's close. If it were me, I'd make the trip to test.

That said, wouldn't be surprised if your impacts shift less than 1" at 100yds, which may not mean much in your <150yd scenario. But you never know until you know...

 

[SDHNTR]

Nothing on paper is going to tell you what might happen with changes in ammo. Bottom line is, you need to re zero.

 

[Annapolis]

Sounds like a trip to the range is in order. If I’m going, I’m taking some other toys to make it worthwhile.

Appreciate the swift and convincing feedback.

 

[Q_Sertorius]

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.

 

[Kyguy]

Change ammo, check zero. One goes with the other. Here's a perfect example of why.... friend of a friend had a Rem 700 Tactical 6.5 Creedmoor. Initial 100yd zero was Hornaday 140gr Match. Couldn't find any locally when he wanted to shoot it again, so he bought some flavor of 130 grain (I don't remember what it was). He went straight to the 200yd 8" gong and couldn't hit it. Back to paper at 100, 3/4" 5 shot group, but it was 12" high and right. It is an extreme example but that's why you check.

 

[Castle Rock]

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.

Total waste of ammo, if 2 or 3 shots are on the money that is plenty good enough for a short range hunting gun

 

[BigNate]

The Deer season xp looks to shoot a bit flatter if I'm reading the chart right. I'd clean the barrel well, and shoot the new ammo. In cartridges like this and short range I don't bother with ten shot groups. Adjust for a zero that makes good sense, save the rest to hunt with.

 

[Q_Sertorius]

Total waste of ammo, if 2 or 3 shots are on the money that is plenty good enough for a short range hunting gun

Do it right, once, rather than farting around with it many times. What you have described is the essence of “penny wise and pound foolish.” The only way to “waste ammo” is to not take well-aimed shots or to take shots from which you learn nothing. That includes making adjustments off of insufficient data. Shooting your rifle carefully and deliberately is never a waste if you learn something from the shot. As long as the shots are on paper (or otherwise spotted), you can learn something from them. For a low-volume rifle, I usually buy 200 of the same lot, devote 20 to sighting in and confirming a good zero, then have the rest to hunt with for the rest of my life.

I’ve watched too many hunters show up at the range before rifle season with one or two boxes of ammo, thinking they will get it sighted in and hunt with it for the entire season. And then they make repeated adjustments off one or two shots chasing the bullseye until they run out of ammo or just stop because they only have a few left. And then they come back with different ammo the next week… and etc. or they just go hunting with a rifle that isn’t really properly zeroed. And that translates directly into missed or wounded animals when combined with field shooting difficulties and nerves.