BP Bore Sighting Question

[RobK]

Guys,
I'm new to the modern inline BP scene and had a question or two to cut down on the initial range time with my new toy.

My wife got me a Winchester Apex 50 cal for christmas and today after putting it together I thought about how to bore sight it before I head out to dial it in. The only thing I could think of was to bench it, pull the breech plug and pick out spot approximately 25 yards away. Once I had that spot centered in the barrel I made a few adjustments to the mounts putting the crosshairs a couple inches lower than the point of reference so that I'm a bit closer to dead on when I actually put hole in the paper next weekend.

Any other suggestions?


Rob

 

[arcticap]

It sounds like a pretty good method, except that due to the fact that the scope is mounted higher than the barrel, I believe that the scope is pointing down at the 25 yard point of aim while the bullet is rising out to 50 yards. You might be shooting 4-6 inches high at 50 yards, it's hard to say depending on the weight and trajectory of the bullet, and height of the scope. But that's good that you'll be on the paper at 50 yards.
Let us know how the Apex shoots and everything works out.

 

[1911 guy]

Bullets don't rise.

I'm going to nit-pick. Bullets don't rise, they begin to succumb to gravity the instant they leave the barrel. What gives the illusion of bullet rise is the line of sight is higher then the bore and not subject to gravity. This means the point of impact will cross the line of sight at two places, giving the illusion of rise in the range between the two intersecting points.

Using your bore sighting method to get on paper, you can get really close with one shot if you have a friend or your wife help you. Fire one shot, make sure it's a good one. Bench the rifle with the crosshairs (I assume it's scoped since it's an inline) on the bull. Do not let the rifle move. Have your "assistant" turn the turrets until the crosshair is on the bullet hole. Your next shot will be pretty darn close to sighted in.

If you are sure the scope is level and you shoot with the rifle level, you can also figure the adjustment by calculating range and adjustment increments at that range. If everything isn't level, you'll just chase holes all over the paper.

 

[RobK]

1911,
thanks, I've zerod many high powered rifles through the years but have never messed with a black powder rifle with scope. the trajectories of a 270gr Powerbelt are alot different at short ranges than 165gr boattail. LOL


Rob

 

[NEW222]

Your method should get you on paper at 100. I have found that when using 100 grains of powder that this usually works. Though our differences in bullets are not much. I was using XTP's 44/240 and 45/250. Also from sighting in my own and friends muzzleloaders I found that 25 and 100 are relatively close. This is only my opinion, but go ahead and you will be alright. Have a good day.

 

[RobK]

Thanks New222. I've never dealt with a scoped ml or a scoped shotgun before as they have a lobbing trajectory.

The load that I'm looking at throwing will be a 270gr Platinum Powerbelt Aerotip in front of 100grains of 777pellet.

The lands I hunt are for the most part 100yard shots or less although there are a few stand sites that could off shots of 150-200.

I'm not going to take shots beyond the 150 mark and that is the range that I will most likely concentrate on zeroing for.


Rob

 

[NEW222]

Having not yet switched to 777, but I would guestimate 80-85 grains would compare to the 100 grains of Pyrodex Select that I shoot. You will want to be around 2-3" high at 100 yards for a 150 zero, if I do remember correctly. I unfortunately haven't shot much this year due to a very dislocatable shoulder. I now have a brace and am ready, but hunting season is well over by time I got my brace. Can't wait till next year. I also had to go get a crossbow cause holding a bow with the shoulder was also risky. Damn, a new toy! Anyways hope this helps and good luck making smoke. Have a good day.

 

[arcticap]

I'm going to nit-pick. Bullets don't rise, they begin to succumb to gravity the instant they leave the barrel. What gives the illusion of bullet rise is the line of sight is higher then the bore and not subject to gravity. This means the point of impact will cross the line of sight at two places, giving the illusion of rise in the range between the two intersecting points.

1911 guy, I think that you're 99.99% right about the perceived bullet rise having to do with the line of sight illusion. However, I recall that there is an exception to the rule when something is fired downward or upward at a 45 degree angle, the projectile does impact above the sight of aim by several inches due to actual rise, and it may be attibuted to physics and gravity. It's even happens to arrows when they're shot downward from tree stands. Have you ever heard of this?

 

[1911 guy]

Pythagorus and shooting.

The pythagorian theorum (high school geometry) states that the two adjacent sides of a right triangle, when squared, will tell you the lenght of the hypotenuse (line connecting you up in a tree to the deer on the ground).

What this actually means is that your eyes tell you it's farther to the deer than it actually is. If you are 15 feet up and the deer is thirty yards away, your eyes see 33.5 yards. The bullet is affected by gravity for 30 yards. This difference gets bigger the higher you are up and the farther the deer is away. A (15 feet up) squared + B (deer at 30 yards) squared = C (what your eyes see) squared.

Adding some more height and range changes things more. If you are twenty five feet up and the deer is fifty yards away the distance your eyes see is now 55.9 yards.

If you set range markers when you hunt from a tree stand, check ranges from ground level and trust your markers.

 

[Froggy]

Picking nits revisited.

The only thing I could think of was to bench it, pull the breech plug and pick out spot approximately 25 yards away. ... Any other suggestions?

With the loads I use in my muzzleloaders (not in-lines), i've found that I can zero at 13 yards and have them right on at 100 yards. You'll still want to confirm with a few shots at 100 yards, but getting it sighted in at 13 yards first should save you some walking back and forth at the range. Check out what Bob Spencer has to say on the topic here:

http://home.insightbb.com/~bspen/sighting.html

I'm going to nit-pick. Bullets don't rise...

Sure they do. Everytime I shoot up at a squirrel, they rise up into that tree. Perhaps what you meant to say is that a bullet does not rise above the axis of the bore, or that one fired from a perfectly horizontal (or declined) bore does not rise above the horizontal plane... and both statements would be true. But any bullet fired from an inclined bore will indeed rise above the horizontal plane. And, because of the trajectories involved, the barrel is usually inclined however slightly upward to get the bullet on target.... and in the process bringing it up to and (usually across) the line of sight. For practical purposes, the bullet rises above the horizontal plane and then crosses it again on the way back down in a predictable trajectory.

True, the bullet is affected by gravity immediately after leaving the bore, but that doesn't mean it is going downward as soon as it leaves the bore. Gravity has to overcome the "up" vector first. It is easier to visualize if you have access to a graphics-based ballistics program. Check out this one:

http://www.norma.cc/htm_files/javapagee.htm

For some reading on practical trajectories, check out these pages:

http://home.insightbb.com/~bspen/ballistics.html

http://www.chuckhawks.com/bullet_trajectory.htm

http://home.insightbb.com/~bspen/trajectories.html

1911 Guy nailed the Pythagorian connection. For more discussion of trajectories when firing up or down hill, check out this page:

http://www.chuckhawks.com/shooting_uphill.htm

 

[1911 guy]

Correct.

That's right, the bullet does not rise relative to the angle it left the bore. If fired from 30 degrees, it will not take a hike toward 40 degrees.

Also, my thought is correct but my math wrong on my last post. I was tired yesterday and didn't convert yards range to feet (up the tree). I was using two different units of measure in one equation. But, the principle is correct.

 

[RobK]

well, got the smoke pole out to an improvised range this past saturday and after pacing off about 50 meters I benched the rifle and decided to see how close the old mk1 eyeball boresighting system worked. first round was 6 inches low and 2 inches right. Not too bad considering the scope was layed by pulling the breech plug and I just looked down the barrel and did my best to line the scope up based on that.

5 rounds fired, scope is now layed for 2.75 inches high at 50m firing 100grains 777pellet behind a platinum 270gr powerbelt aerotip.

GAME ON!!

r