Let's say you zero your .308 at 100 yards with 150 grain ammo. Then you switch to a 165 or even a 180 grain cartridge. How much difference are we talking in 100 - 200 yards?

How about a .223 in 55 grain vs say 75?

Way to many variables, different guns shoot different loads in different spots. You could get lucky and have them all shoot in the same group, but that is extremely unlikely,.

Pretty much agree with the above. I went from 62 to 75 grain in a long barrel AR I have and didn't have to change my scope zero very much at 100 yards. I also went from 150 to 165 grain 30-06 in my Remington 700 and the point of impact was way different and I had to readjust quite a bit.

Just have to find out for yourself with the specific rifle/ammo combination.

Stay consistent. Eot

Yep. Just find out what works and be consistent. Keep in mind that different bullets may shoot differently left to right. So you can't just assume the heavier grain will keep the same line but drop a little more. If they're vertically on the same line, then 100-200 yards won't be much different in a hunting situation. Could be a very big deal much beyond that.

Powder type and charge weight are just important as bullet weight (if not more so) in determining POI. Seating depth (the resulting "jump" actually) and primer type also make a difference, not to mention your rifle's own barrel harmonics. As stated above, way too many variables to predict that outcome with any certainty at all.

You can try a calculator to get in the ballpark. Calculate your current load, then the proposed load to see the difference. You'll also need to determine the ballistic coefficient, but there's a calculator for that on this page too: http://gundata.org/ballistic-calculator/

Edit: here's an example of the differences in a couple of random 308 bullets - one 150 grain and one 180 grain. Note they are different bullets with different ballistics, so results will vary.

Everybody pretty much nailed it. Zero with what ya wanna hunt with. If something super common that ya can find at walmart works, then that's great. Either way buy multiple boxes at once.

Latest personal experience:

Zero'd my 7mm-08 with some 140 gr Federals.
Then tried 139 gr Hornady SST's. They were about 3-4" high and to the left, and the grouping was way to large for my liking.
Then tried 150 gr Hornady ELD-X, They were 1" higher but directly inline with the 140 gr Federals.
Finished off the Hornday at different ranges to calculate some drops.

I bought 3 more boxes of the ELD-X, and I'm halfway through the first box after 2 years.

Agreed. Of all of my deer rifles my favorite killer is my 1968nRemington 760 in 30-06. It is probably my cheapest too. But it is a point and shoot killer and I really like the pump action(im left handed).

Anyway I figured out after trial and error that it shoots 150grain Federal Sierra Gamekings and Remington Core Lokts thru the same hole. The only real difference is the GameKings may keep a tighter pattern. So I buy a lot of both.

Also, it shoots 180gr CoreLokts 2-3 inches lower than the 150. I remember trying out another box of 150, may have been Hornady, and it was like 4 inches left.

I used to do a lot of reloading in years past. I have a buddy that I loaded ammo for his .270, but he wanted two different grain bullets loaded- one for whitetail and one for mule deer. I did some research with my RCBS manual and was able to do this with him not having to re-zero his scope when changing. It can be done when you use one distance for your point of reference. Any distance other than that could probably have a different POI.

OP, to actually answer your question...the bullet weights you describe in your post will only vary at 100 yards by an inch or so.

There may be windage (left, right) variance as well. But it's likeky in that same inch or two range unless it's a load your riflecreally doesn't like.

If you zero with the light weight bullet you will find the heavier billet will print higher on target. The lighter bullet being faster has a more flat trajectory.

It's good to know what other ammo does in your rifle with your zero. You never know when you may find yourself with the wrong ammo. Some experimental shooting now can save the day later.

The better ballistic apps also allow you to input data with alternate zero offsets. That way you can zero with one ammo, fire a second type, note the offset in the app and it will correct your holds all the way down range. Comes in handy when you may be shooting several different types of ammo (AP, barrier, OTM, or limited penetration) depending on the circumstances.

In 3Gun, we zero with 75/77 for use at distance. But for shooting under 200 yards we run 55 grain ball. It's cheaper, and the targets don't seem to care.

As always YMMV.

Puryear Playboy said:

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OP, to actually answer your question...the bullet weights you describe in your post will only vary at 100 yards by an inch or so.

There may be windage (left, right) variance as well. But it's likeky in that same inch or two range unless it's a load your riflecreally doesn't like.

If you zero with the light weight bullet you will find the heavier billet will print higher on target. The lighter bullet being faster has a more flat trajectory.

It's good to know what other ammo does in your rifle with your zero. You never know when you may find yourself with the wrong ammo. Some experimental shooting now can save the day later.

The better ballistic apps also allow you to input data with alternate zero offsets. That way you can zero with one ammo, fire a second type, note the offset in the app and it will correct your holds all the way down range. Comes in handy when you may be shooting several different types of ammo (AP, barrier, OTM, or limited penetration) depending on the circumstances.

In 3Gun, we zero with 75/77 for use at distance. But for shooting under 200 yards we run 55 grain ball. It's cheaper, and the targets don't seem to care.

As always YMMV.

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I'll have to disagree, based on empirical data observed. Firearms (rifles) have an uncanny way of providing results you "have to see to believe". Simply switching brands of an equal weight has resulted in 3-4" shifts in POI (though groups size may be comparable). One of my reloads in a 22K Hornet would shift POI left by 2"...by changing powders!

Regarding light bullets (zeroed) versus then using a heavier bullet; for a given distance, the heavier bullet will (generally) hit lower, due to its poorer trajectory...or did I miss something (no pun intended)?

The lighter bullet having usually higher muzzle velocity will have a flatter trajectory initially.

But, what do I know. Go shoot and see.

GSS said:

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Puryear Playboy said:

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OP, to actually answer your question...the bullet weights you describe in your post will only vary at 100 yards by an inch or so.

There may be windage (left, right) variance as well. But it's likeky in that same inch or two range unless it's a load your riflecreally doesn't like.

If you zero with the light weight bullet you will find the heavier billet will print higher on target. The lighter bullet being faster has a more flat trajectory.

It's good to know what other ammo does in your rifle with your zero. You never know when you may find yourself with the wrong ammo. Some experimental shooting now can save the day later.

The better ballistic apps also allow you to input data with alternate zero offsets. That way you can zero with one ammo, fire a second type, note the offset in the app and it will correct your holds all the way down range. Comes in handy when you may be shooting several different types of ammo (AP, barrier, OTM, or limited penetration) depending on the circumstances.

In 3Gun, we zero with 75/77 for use at distance. But for shooting under 200 yards we run 55 grain ball. It's cheaper, and the targets don't seem to care.

As always YMMV.

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I'll have to disagree, based on empirical data observed. Firearms (rifles) have an uncanny way of providing results you "have to see to believe". Simply switching brands of an equal weight has resulted in 3-4" shifts in POI (though groups size may be comparable). One of my reloads in a 22K Hornet would shift POI left by 2"...by changing powders!

Regarding light bullets (zeroed) versus then using a heavier bullet; for a given distance, the heavier bullet will (generally) hit lower, due to its poorer trajectory...or did I miss something (no pun intended)?

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I put this theory to the test today, and he is right on. I shot five groups of 3 with my 308 with 150 grain Winchester XP and did the same with 150 grain Remington Core Lokt. Both had pretty consistent groups at 100 yards but the Core Lokt group was about an inch higher.....every time.