Basically I'm sighting it in for deer, it will probably get used for beavers and possibly coyotes too but that's a different discussion. I have a 3.5-10x50mm scope on it. I certainly have no need to go beyond 300 yards without compensating for bullet drop. Any comments or suggestions are appreciated.
Buckmaster is right, Zeroed @ 200 yards will put you +1.5 " or a bit better @ 100 yds and about - 6.5 or so @ 300 yards. The secret is remembering these #'s so when the time comes there is no wondering " Was it 7 inches or seventeen,maybe twenty-two, no that's the barrel length"
And ballistic charts are just a Guide, all rounds will not act the same in every firearm.
After you determine the velocity.
A trajectory chart will give you the flight at a variety of sightings.
I like to set my sights to a 7" target. Use the chart that puts the trajectory of the bullet at a maximum of 3 1/2" above the line of sight, during trajectory. At the point it is 3 1/2 low of sight is your max pbr. The height the bullet is at, at the 100yd mark. Is where you sight at.
example: If the chart says it is 2.3 inches high at 100yds.
When you physically site the rifle. Sight it so the the bullet is hitting 2.3 high of sight, at 100yds.
If you prefer an 8" target. Use the chart that puts the bullet at a max of 4" high. At 4" low is your max pbr. Site at the reading at 100yds.
Using this scenario will allow you to aim dead center of your target and get a good hit, out to your max pbr.
Don't disregard winddrift.
If, at the velocity of your bullet. With a 20 mile an hour cross wind the bullet drifts 3 1/2". Then you can still hold dead center on your 7" target and get a good hit out to your max pbr.
I would assume that either load will give you 3100 fps. That might be optimistic. Like fuzzybear, I like the max point blank range at some specific size target. That target size makes a difference. On the chest of a deer you have about a 9 or 10" kill zone, on the coyote maybe 6" and on the beaver I'm guessing 3" ?
The idea of MPBR is to keep the bullet in the kill zone as long as possible befor having to compensate for trajectory by holding either under or over the target. Many year's ago some gun writter came up with the idea that something like 3 1/2" high at 100 yds was the way to go as it maximumized the trajectory potentional of the cartridge. For big game and most high intensity cartridge's, your 270 is one, that work's very well. Just understand that the MPBR will change depending on the velocity of the bullet.
None of this give's you an answer to your question because there really isn't one given the size difference in the animals you want to use your rifle on. Perhaps if you were to split the difference between the smallest and the largest you'd be there. So the difference between 3" and 8" would make the target size 5.5". Next assuming you do get 3100 fps with the load;
MPBR 285 yds
MPB zero 247 yds
MRT about 137 yds (bullet will be at highest point +2 3/4")
zero @ 100yds +2.2"
impact @ 200 +1.8"
Drop @ 300 -3.7" (your still on the deer size target.)
Losing velocity from 3100 fps will change this some what but this would be close. You need to sight in then go shoot at paper target's to see where your really at.
Thanks for all the replies. Don, that's exactly what I was looking for, how do you come up with those numbers? computer program, lots of equations? I was trying to figure that out just by looking at ballistics charts from the manufacurers and then I could get to the nearest 50 yards.
I have a Pact Mk IV cronograph with a trajectory computer in it. I've run a lot of load's over it then sighted in with he data off it and it's very accurate. If you want remaining energy I can give you that formular, it's simple:
velocity x velocity devide the answer by 7000 (# grains in a pound) devide that answer by 64.32 (specific weight of gravity) and multiply that answer by the weight of the bullet in grain's. Example: your 130 gr 270 laod at 3100 fps has 2884.7 fps remaining velocity at 225 yds. My cronograph prints it out for me.
At 225 yds you have 2402.7 ft lbs remaining energy.
At 300 yds it's 1698.5 lbs
By the way, I know I can do to 700yds in 25 yd increments, maybe farther and closer increment's, maybe.
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