same weight/ same POI ?

[Bart B]

Another qualifier to the question is changes to seated ogive distance to lands -w/resp to a gun's personality. This, because tune greatly affects POI.
And going from a tangent ogive to secant for example, all else equal, can have a big affect on POI and performance in general until optimum seating is again determined.

I can't imagine changing bullets, even lot to lot of the same, without seeing some difference.

In two different 30 caliber rifles shooting both 150 and 172 grain bullets, each with different ogive and jump to lands distances varying about .040", the difference in point of impact at 200 to 300 yards was less than 1/2 MOA.

And across several .308 Win. barrels shooting different lots of 168 and 190 grain bullets in each one, I never saw more than 1/4 MOA change in each ones point of impact from 200 through 600 yards.

I can imagine changing bullets, even lot to lot of the same, without seeing any significant difference. Especially at the shorter ranges.

 

[ken snyder]

Mada I generally have more than 1 bullet with me. a tough heavily constructed hunting bullet and a long range Target type bullet. The my rifles are set up for maximum expected yardages with the long range bullets and generally carried with hunting bullets. An Example: if a 10 inch group is acceptable at 1000 yds. ( vitals zone) then it is also acceptable at 100 yds. the differences are not that dramatic for the hand loader but that is the idea. If the same 100 yard zero is actually the goal the answer is definitely yes but both loads would probably need tayloring'. but at short ranges for hunting no practical difference and easy to do if that is your goal.

 

[Bart B]

An Example: if a 10 inch group is acceptable at 1000 yds. ( vitals zone) then it is also acceptable at 100 yds. the differences are not that dramatic for the hand loader but that is the idea.

I doubt anyone on these forums will put their first shot inside that 10 inch vital area at 1000 yards more than 10% of the time in hunting conditions afield.

I know I can't even do that on a thousand yard rifle range with known zeros and a .6 MOA rifle and ammo.

 

[ken snyder]

Mada I generally have more than 1 bullet with me. a tough heavily constructed hunting bullet and a long range Target type bullet. The my rifles are set up for maximum expected yardages with the long range bullets and generally carried with hunting bullets. An Example: if a 10 inch group is acceptable at 1000 yds. ( vitals zone) then it is also acceptable at 100 yds. the differences are not that dramatic for the hand loader but that is the idea. If the same 100 yard zero is actually the goal the answer is definitely yes but both loads would probably need tayloring'. but at short ranges for hunting no practical difference and easy to do if that is your goal.

 

[rscott5028]

The answer is that the trajectories are different.

The question is whether or not it's significant for your situation.

Here's an example based on 2 factory loads...

Federal Gold Medal: 308 Win 168g Sierra MatchKing BTHP
BC=.463
2650fps, 10mph wind from 3 o'clock
100yds, elev=0, windage=.75
300yds, elev=4.75, windage=2.25
500yds, elev=11.75, windage=4.25
700yds, elev=21, windage=6.50

Federal Gold Medal: 308 Win 175g Sierra MatchKing BTHP
BC=.513
2600fps, 10mph wind from 3 o'clock
100yds, elev=0, windage=.75
300yds, elev=5, windage=2.25
500yds, elev=12, windage=3.75
700yds, elev=20.75, windage=5.75

 

[Bart B]

The answer is that the trajectories are different.

Federal Gold Medal: 308 Win 168g Sierra MatchKing BTHP
BC=.463

Federal Gold Medal: 308 Win 175g Sierra MatchKing BTHP
BC=.513

That's the difference between the short boattail on the 168 and the long one on the 175.

Sierra changed their original 30 caliber 180-gr. HPMK's boattail from the long one to a short one made to the same specs as their 168. It never shot as accurate as their old ones. The US Army team contracted Sierra to make their 180's with the longer boattail under special order; they knew they were more accurate at the longer ranges.

 

[Mada]

I shoot a Hornady 150gr FMJ and a Hornady 150gr SST in the same rifle. The charge weight is .5grains different, the BC is .017 different; the POI difference is less than moa at 400 yards.

So I practice with the FMJs that are 2/3s the price of the SSTs.

This is exactly the answer I was hoping for.. See, what I want to do is use Hornady 162gr SST and 162gr A-Max. So I can switch between the two bullets depending on my target. THANK YOU !!

May I ask why the your charge weight is different? Is it just because. Or velocity issues. Or whatever the case may be..

 

[justgoto]

May I ask why the your charge weight is different? Is it just because. Or velocity issues. Or whatever the case may be..

Whenever I change a component to a load, I'll preform another ladder test. In that instance, I found the FMJ load to be most accurate with an increase in charge weight.

 

[Mikecr]

Whenever I change a component to a load, I'll preform another ladder test. In that instance, I found the FMJ load to be most accurate with an increase in charge weight.

This is the type of qualifier I was talking about. In my experience changing bullets changes tune, and justgoto is taking the right action here. Without this, POI would change in my guns if I picked from multi-bullet selections in the field.
Maybe I'm missing the context of this question though.

 

[Trickymissfit]

I shoot a Hornady 150gr FMJ and a Hornady 150gr SST in the same rifle. The charge weight is .5grains different, the BC is .017 different; the POI difference is less than moa at 400 yards.

So I practice with the FMJs that are 2/3s the price of the SSTs.

That's not much of a difference to ever worry about, but when you start to look at a .1 or larger difference it starts to show up fast. I personally would not worry about .05 or even .075 in the B/C, but I try to keep my shots under 600 yards.
gary

 

[Trickymissfit]

This is the type of qualifier I was talking about. In my experience changing bullets changes tune, and justgoto is taking the right action here. Without this, POI would change in my guns if I picked from multi-bullet selections in the field.
Maybe I'm missing the context of this question though.

exactly! Compair a 200 grain flat based bullet to a 200 grain boat tail at 350 yards in a 30 caliber like a .300 mag.
gary