Maximum Point Blank Range (MPBR) -- Help zeroing my rifle

[Godspanther]

TL;DR Summary

Using math to determine optimal distance at which to zero my rifle

I have been attempting to calculate optimal zero for my H&R 30-30.
190g
170g
160g
150g
These links are the optimal zeros for my rifle based on each of the four grain weights available to fire thru the rifle. I don't want to have to re-zero my rifle every time I switch between ammo types so I need to figure out the optimal distance at which to zero the rifle to get maximum performance from one zero setting for all ammo types. Not sure of the best way to figure that.

 

[Baluncore]

You will need to tabulate the elevation of each projectile as it travels away from the horizontal muzzle.

The sights can then be set, looking down at an angle from above the horizontal bore line. For each different load type, there will be two ranges where the projectile passes through the crosshairs of the sight. At the first it will be rising, close to the muzzle, at the second it will be falling. There will also be one highest point in each trajectory. You will need to Chebychev optimise the zero of the sights for the different trajectories.

Computationally, the drag coefficient of the projectile will vary with air speed. Initially, the horizontal deceleration due to drag will be maybe between 50 and 100 times the acceleration downwards due to gravity. That velocity will fall, and the drag will change, until at the end of the trajectory, gravity will dominate.

Just how you zero the sights will depend on the size of the target and the typical ranges for that target.

 

[Godspanther]

How I zero the sights is based upon a theory of no more than 6 inches above bullseye at the height of the bullets arc. I have posted this question on other forums and since first posting it was pointed out to me that barrel twist plays into the equation. Mine is a 1 in 10 twist and while that can potentially stabilize bullets above 168g it is optimal for 150 & 160g. While the issue has not been totally settled yet and I am waiting to see if other pertinent factors come to light it is beginning to appear as though zeroing based on lowest common denominator may be my best choice. And so far that translates to an 18 yd zero.

 

[Baluncore]

And so far that translates to an 18 yd zero.

That is the first rising zero of the two crossings.
Design using your 6 inch rule, for the load that flies highest.
Draw a line from the sight, that passes 6 inches below the tangent to the top of the trajectory. Read off the range for the first line crossing, then use that range for setting the sights to zero.

 

[berkeman]

I don't want to have to re-zero my rifle every time I switch between ammo types

Why do you want to be able to switch bullet weights?

 

[Godspanther]

Why do you want to be able to switch bullet weights?

Because I want to be able to shoot various types of ammo and still be reasonably sure of hitting my target. For example if I am just shooting for fun at paper targets I'd want to use cheaper 150g or 160g bullets. If I am out hunting I'd want the heavier 170g or 190g bullets for their shear stopping power. I'm not sure what you know about shooting but forget the media hype. How effect or dangerous a weapon is, is not determined by the gun so much as the bullet.

 

[berkeman]

I'm not sure what you know about shooting but forget the media hype. How effect or dangerous a weapon is, is not determined by the gun so much as the bullet.

LOL. I've been hunting for decades, and accuracy is the most important thing in my experience. A few extra grains of bullet weight means little if you gut-shot your target instead of a clean shot. My advice is to ditch your current thinking and instead use the lightest bullet in that range to get the highest velocity and corresponding least drop over your effective range. I shoot .270 130 grain for that reason. +/- an inch out to 200 yards.

 

[Godspanther]

If you note the links in my original post I may use the lightest bullet measurement when zeroing the rifle [lowest common denominator] but since I have multiple weights in my inventory I will stick with the heavier 190g for when I mean business. Buffalo Bore Heavy 30-30 That would still reliably put me withing 6" of dead center clear out to around 255yds with an 18yd zero.

 

[berkeman]

If you note the links in my original post I may use the lightest bullet measurement when zeroing the rifle [lowest common denominator] but since I have multiple weights in my inventory I will stick with the heavier 190g for when I mean business. Buffalo Bore Heavy 30-30 That would still reliably put me withing 6" of dead center clear out to around 255yds.

Whenever I shoot an animal to put it on my dinner table, I always mean business, and strive to minimize any suffering by my prey. That's why I shoot the lightest bullet and put it where I intend to (plus or minus an inch). I'm starting to get a pretty weird vibe from your newbie posts here.

What game do you hunt with your 30-30? Are you hunting with open sights or a scope? If a scope, what power(s)?

 

[Godspanther]

It has a cheap 14x Burris scope. I originally intended it merely as a deer rifle but since discovering the existence of the heavier ammo have been considering branching out. However I am a bit hesitant about that since my 30-30 is only a single shot H&R Handi-Rifle. I'm a decent shot but with a bear or moose you kind of want backup just in case of s***.

 

[berkeman]

However I am a bit hesitant about that since my 30-30 is only a single shot H&R Handi-Rifle. I'm a decent shot but with a bear or moose you kind of want backup just in case

I don't think that a 30-30 is appropriate for hunting bear or moose. I don't think I would hunt those even with my .270, and I would not bother upgrading to 150 grain in an attempt to make my wound channel a little bit larger. I do have a 30-30 that I use for very close quarters brush bucking for deer.

I would probably invest in a .300 Win Magnum rifle to go after larger game like that. Plus, I haven't ever tasted bear, but it's hard to believe they taste better than deer (backstraps and jerky).

 

[Godspanther]

Perhaps you did not see the link I posted to Buffalo Bore Heavy 30-30? Supposedly that load is capable of the task. In any case I have had bear and it is quite tasty. How do you like to do your venison? I have 2 favorite ways. For the more tender cuts I like to salt them the night before then pepper & smoke them, low and slow. For tougher cuts I like to chop them into small pieces & braise them before turning the braise liquid into a rich creamy gravy filled with venison chunk to serve with potatoes.

 

[Vanadium 50]

The trick to moose is not shooting them. Its convincing them to get on the flatbed of your truck first.

 

[Godspanther]

That would be an impressive trick.

 

[berkeman]

Perhaps you did not see the link I posted to Buffalo Bore Heavy 30-30? Supposedly that load is capable of the task.

Correct, I missed that:

Buffalo Bore Heavy 30-30

From that link:

Buffalo Bore is introducing a truly Heavy 30-30 Winchester loading. This new load utilizes a 190gr. custom Hawk Bullet and gives the venerable 30-30 here-to-for unrealized power and is designed so that the person who owns a 30-30 can now reliably kill elk or moose sized game. The 30-30 can now be carried as a defensive tool in grizzly country and will be much more effective in stopping a grizzly attack than any other 30-30 ammunition in the world. This heavy 30-30 load is not designed for deer, although it will kill deer and if you line them up right, it will kill three or four deer with one shot……….

So it is just the heavier bullet that is different, or are the loading it as some kind of a magnum round? They seem to imply you can still shoot it out of a standard 30-30 rifle (like I have in addition to my .270), so it must not be too much of a magnum load.

How do you like to do your venison?

After experimenting over the years, I settled on keeping the backstraps and making venison jerky out of the rest of the meat in my smoker. My friends and I love venison jerky, so it's great to be able to enjoy the result of the hunt with them for several months. For the backstraps, I've learned how to butterfly them and cook them in a light lemon sauce. Yummy!