.308 ballistics question

[npaull]

Hi all,

I am hunting blacktail this fall for the first time with a rifle (I've hunted with a bow for over 20 years, drew a rut tag, bought a Henry single shot .308, intend to use it this season).

I got the rifle pretty nicely sited-in with 165 grain bullets. Recently on sale I bought a bunch of 180 gr bullets by accident (thought they were 165 and was mistaken).

Am I correct that for hunting purposes, taking shots of 100 yards or less (maybe 150, I very much doubt farther given blacktail country) that this won't affect my site-in too much to worry about?

I welcome any opinions. I am going to take some shots before Nov 1 and I'll tinker, but thought I'd ask anyway.

[Hilltop123]

Take 5 rounds and find out, you have time.

[npaull]

I will. But I would still like opinions.

[bobcat]

I would either shoot it with the 180 grain bullet, and adjust as necessary, or go back to the store and get a box of cartridges that's exactly the same as what you're sighted in with. I wouldn't feel confident hunting with it otherwise. But chances are your point of impact will only be two or three inches different at 100 yards. It could be more, and there's just no way of knowing without shooting it with that load.

[Dan-o]

I would either shoot it with the 180 grain bullet, and adjust as necessary, or go back to the store and get a box of cartridges that's exactly the same as what you're sighted in with. I wouldn't feel confident hunting with it otherwise. But chances are your point of impact will only be two or three inches different at 100 yards. It could be more, and there's just no way of knowing without shooting it with that load.

 

[Yondering]

Am I correct that for hunting purposes, taking shots of 100 yards or less (maybe 150, I very much doubt farther given blacktail country) that this won't affect my site-in too much to worry about?

No, you should absolutely expect it to change your zero point. Any ammo change, but especially bullet weight, can change point of impact and more in some rifles than others. Any guesses as to which direction it'll change at 100 yards are just guesses, you need to shoot it to find out.

[PlateauNDN]

I like the 180 great match points for my .308. Shot really good groups with them.

[jrebel]

From a bullet weight perspective....no the 15 grains difference won't make a difference out to 100 yards.  Now....... different bullet, different powder, rifle like or dislike......those favtors make all the difference in the world.  Same holds true with same weight bullet with different box ammo manufacturers.......gun may like one and not the other.  Go shoot them and make sure it shoots well.  Easy....fun.....and most importantly most ethical for the deer you want to hunt. 

[WapitiTalk1]

What JR said 

[wadu1]

From a bullet weight perspective....no the 15 grains difference won't make a difference out to 100 yards.  Now....... different bullet, different powder, rifle like or dislike......those favtors make all the difference in the world.  Same holds true with same weight bullet with different box ammo manufacturers.......gun may like one and not the other.  Go shoot them and make sure it shoots well.  Easy....fun.....and most importantly most ethical for the deer you want to hunt.

No  about it

[Bob33]

At 100 yards or less it will more than likely not make enough difference to worry about on a deer. If you can shoot the different load you will know for sure.

[npaull]

10-4 on the need to shoot the new bullets, and I most certainly will (as intended). Thanks all.

[SteelheadTed]

I'd go back and get the same ammo you've already been shooting.  It works, why mess around?

What happens when you run out of the sale ammo?  Are you going to go back to the 165? 

[yakimanoob]

From a bullet weight perspective....no the 15 grains difference won't make a difference out to 100 yards.  Now....... different bullet, different powder, rifle like or dislike......those favtors make all the difference in the world.  Same holds true with same weight bullet with different box ammo manufacturers.......gun may like one and not the other.  Go shoot them and make sure it shoots well.  Easy....fun.....and most importantly most ethical for the deer you want to hunt.

Couldn't have said it better myself. 

[Bill W]

The 15 grains difference between bullet weights isn't the main problem. It's barrel harmonics and where the end of the barrel is pointing when the bullet exits.   The new loads needs to be sighted in and scope adjusted.   Not confirming where things hit and adjusting sights is just plain wrong.

[Yondering]

From a bullet weight perspective....no the 15 grains difference won't make a difference out to 100 yards.  Now....... different bullet, different powder, rifle like or dislike......those favtors make all the difference in the world.  Same holds true with same weight bullet with different box ammo manufacturers.......gun may like one and not the other.  Go shoot them and make sure it shoots well.  Easy....fun.....and most importantly most ethical for the deer you want to hunt.

Couldn't have said it better myself.

Lots of guys congratulating this comment that got the most significant factor wrong. 15 grains of bullet weight difference absolutely can make a difference in point of impact at 100 yards, even if all else is equal. That's not because of the difference in trajectory, but the difference in barrel time when the bullet exits, as Bill W said.

[yakimanoob]

Yondering, I can't speak for the rest of the folks, but to me the difference in the barrel harmonics was covered in the "rifle like or dislike" part of jrebel's comment. 

The overall point, I think, is that it's not the single variable (weight) that's important, but rather the simple fact that it's different ammunition, and you should always verify after an ammo change. 

[Yondering]

Yondering, I can't speak for the rest of the folks, but to me the difference in the barrel harmonics was covered in the "rifle like or dislike" part of jrebel's comment. 

The overall point, I think, is that it's not the single variable (weight) that's important, but rather the simple fact that it's different ammunition, and you should always verify after an ammo change.

And yet, that difference in weight is generally the biggest factor contributing to change in point of impact. Don't marginalize the most important detail, as jrebel did.

[jrebel]

Yondering, I can't speak for the rest of the folks, but to me the difference in the barrel harmonics was covered in the "rifle like or dislike" part of jrebel's comment. 

The overall point, I think, is that it's not the single variable (weight) that's important, but rather the simple fact that it's different ammunition, and you should always verify after an ammo change.

And yet, that difference in weight is generally the biggest factor contributing to change in point of impact. Don't marginalize the most important detail, as jrebel did.

Some people just like to argue ......  LOL.

No one marginalized anything......you are over analyzing what I said.  The fact is, if you change something..... anything.....you should verify POI......PERIOD.   Any one factor can change POI.   Bullet weight (15 grains)......all else being equal.......will not be enough of a weight change to drastically effect a rifles POI at 100 yards.  I can prove it if you want but you have to buy the powder ......  LOL!!! 

Cheers

[Yondering]

Bullet weight (15 grains)......all else being equal.......will not be enough of a weight change to drastically effect a rifles POI at 100 yards.

That is absolutely wrong, and it's not overanalyzing anything to say so. Go prove it for yourself, I've already seen it plenty of times. It doesn't have the same effect in every rifle either.

[jrebel]

Bullet weight (15 grains)......all else being equal.......will not be enough of a weight change to drastically effect a rifles POI at 100 yards.

That is absolutely wrong, and it's not overanalyzing anything to say so. Go prove it for yourself, I've already seen it plenty of times. It doesn't have the same effect in every rifle either.

Like I said......some people just like to argue.  Liberal propaganda......pic a part of a quote and disagree......even though the overwhelming message is anything / any change can change POI......your killing me smalls.  Take a 22 mag and change bullet weights and tell me at a reasonable distance 50-75 yards it drastically changes poi!!  It won't.....

Note I am referencing your tactics as liberal propaganda not you......though I expect an argument on that topic too. 

[jasnt]

I have one extreme example with my old 243 barrel. I shot 2 different loads most of its life
62gr Berger column and the 95gr vld
Both had very different poi. When zeroed for 95’s I decided to go hunt coyote and went out to adjust my zero for the 62’s which I hadn’t shot for a long time.  With no adjustment the shot hit 4” high and 6” right.  I thought I had a problem with my scope so I shot a 95. Dead center. Shot another 62 and same 4” low and 6” right with shots touching.  So I loaded up my 10 round mag alternating 95’s and 62’s.  I printed 2 nice groups one being centered and the other 4” low and 6” right.

Only thing I can think of was just an extreme difference in harmonics.  This is an extreme example and the most I have seen in my rifles but was very repeatable.   

You won’t know for sure till you try.  FWIW my new barrel has zero poi shift at 100 yards between 105gr and 115 gr vlds