accuracy with different loads

[cbanman]

I worked up some reloads for my new savage 7mm-08 last night. My goal was to produce a coyote round and a whitetail round. I'm a little new to reloading so I lack some of the tricks and techniques that experience brings. Anyhow, I prepared all my cases identically, cleaned, resized, trimmed etc.. The coyote rounds consisted of 100 gr Sierra hollow points using varget powder. I sighted these in at 75 yards. Groups were around 1". To get the point of impact centered on the target, I had to max out my left right adjustment on the scope as far right as possible.

The whitetail rounds were 140 gr sierra boat tail soft points. Again I used identical cases. The powder used on these rounds was varget also. At 75 yards, these bullets grouped relatively well also at about 1". The problem was that the whitetail rounds point of impact was about 5 inches right and 4 inches lower than the coyote rounds. One other big difference besides the bullet used was the overall cartridge length. Due to the small size of the 100 grain bullets these cartrideges were signifcantly shorter than the 140 gr rounds. I made sure to seat these bullets at least as deep as they were wide. The seating depth was about 0.290". I kept the whitetail rounds at just a little under the 2.800" max length for the 7mm-08.

I guess my question is, should the POI be that much different in the two rounds? Is there anyway I can bring these groupings in close together so that I don't have to adjust the scope to hit where I am aiming when switching loads?

I also read about the importance of the lands to bullet distance. How can I determine this and how important/significant is it?

[Slamfire]

Take a fired case, with the neck partially resized. Put a long flat based bulllet in nose first, and chamber the round. When you extract it, it ought to reflect the distance from the bolt face to place where the rifling begins (the leade). Put that bullet where it won't get lost of banged around. Take another bullet from the same box and insert it as square as you can into the muzzle until it contacts the rifling, push on it a bit and twirl it around so the rifling engraves a mark on the ogive of the bullet. Now seat this bullet so that the distance between the base of the case and the ring around the bullet are the same length as the first dummy round you made. Set up your seating die using this second round. Now any bullet seated by the die will touch the rifling in the rifle. Turn down the seating stem until it will seat the bullet of the second dummy a bit further into the case. Measure the base to line distance. However much shorter it is will be the difference between the bullet and the rifling. I generally start a 0.20" bullet to land distance and shoot a bunch of these loads. If I'm not satisfied, I seat the next batch of bullets a bit deeper, and so on, and so on, until I'm happy. Then I save the second dummy round with the bullet info scratched on the case. I repeat the process for every bullet I load for, keeping the dummy rounds to simplify setting up the seating die when I want to load some more rounds with that bullet.
Or you can by the Sinclair oal tool and follow the directions.
As for the divergence in the bullet strikes on the target I can't help you each rifle barrel vibrates differently with different bullets. Perhaps you can find a way to dampen the barrel vibrations, like the BOSS system. If you don't sell these dampeners to your friends and neighbor's you won't be violating the patent.
Lastly, good luck.

[HighDesertWolf]

if it were me , id just stick with the 140's and forget about the 100 grainers. the 140 grain sierra's will kill coyote's just aswell as it will kill deer. I want to ask why you decided on the 100 grain bullets for coyotes? I mean if you were soley gonna be hunting yotes then the 100 grain bullets would be fine.

[vangunsmith]

Your never going to get them to shoot the way you want.Its like the difference between apple and oranges. No matter what you do. Have you tried 120 gr bullets? You should have enought adjustmen in your scope,rather than what you have. Are your bases non-adjustable? What kind of scope? All barrels are different when it comes to different bullet weights,no matter what some people think IMHO. Vangunsmith

[cbanman]

I have a Simmons Whitetail Expedition (4-12X42) scope mounted on the Weaver style bases. The bases are not adjustable. Thus far I've only tried the 100 gr and 140 gr. I may look into some 120's and see how they fly.

[Slamfire]

Why not compromise and shoot the 130s they are designed for medium game which includes both coyotes and deer.