Confusing bullet drop at 100 yds

[Roger B]

I have a Rice match grade 1" .54 (1/66") that I've been working with lately which has been driving me crazier than usual. I've been shooting a .535 ball with Belgian linen patching & Hoppes for lube. With 65-75 grs of Goex FFg
I have it in the X ring at 25 & 50yds, but everything goes wrong at 100yds. With up to 90grs its shooting 6" low at 100yds with very satisfactory groups. When I get it in at 100yds, I'm 6" high at 25. The only thing I can think of is that my vision/sight picture is faulty. The groups are way too good for flinching & I can't imagine that the barrel is faulty. Other ideas? I have to admit that I have to use a 200yd target in order to get sight definition that far.
Roger B.

[smallpatch]

Roger, sounds like its doing what it should.
How far high is your 50 yard?

[Flint62Smoothie]

Sounds right to me, i.e., whether 6" low @ 100Y or high @ 25Y, you have a perfect match for your trajectory!

If keeping 'as is', simplest ... , sight for the 6" low @ 100Y and aim at the the top of the back of the deer at that distance.

Or this is what I do and could possibly help, do load development for tightest group from 75 - X grains, then sight in at 75Y and determine the holds for the other distances.

[Roger B]

Dane;
I haven't had time to get it back to 50 yds, but I've never had this problem before. I can usually get a gun to shoot at 25 & 50yds, & then add about 10-15grs to get in the 10 ring at 100yds. Just confusing to me.
Roger

[Molly]

http://www.ctmuzzleloaders.com/ctml_experiments/rbballistics/web_apps/rb_ballistics.html

[Eric Krewson]

I have about the same barrel, on at 50 puts me 8" low at 100 with 80gr of 2F.

[WadePatton]

Actual drop is a function of velocity, no matter how it's sited. 

Is that 50 ball running approximately the same speed as the other loads to which you make comparison?

[D. Taylor Sapergia]

Roger, I have a solution for sighting your rifle that works well for me at least.
On the blade of my front sight, I file a 45 degree slope on the back top corner and polish it.  It is only as long as it is high, so is a square of polished silver, that when sighting appears to be round.  I sight my rifles to strike point of aim at 25 and 50 yards, then for 100 I hold the illuminated ball of light its diameter above the notch and the top of the rear sight to give me a 100 yard picture and centre strike.  Try it (and report back your findings, please).

[Daryl]

I have a Rice match grade 1" .54 (1/66") that I've been working with lately which has been driving me crazier than usual. I've been shooting a .535 ball with Belgian linen patching & Hoppes for lube. With 65-75 grs of Goex FFg
I have it in the X ring at 25 & 50yds, but everything goes wrong at 100yds. With up to 90grs its shooting 6" low at 100yds with very satisfactory groups. When I get it in at 100yds, I'm 6" high at 25. The only thing I can think of is that my vision/sight picture is faulty. The groups are way too good for flinching & I can't imagine that the barrel is faulty. Other ideas? I have to admit that I have to use a 200yd target in order to get sight definition that far.
Roger B.

Roger, have you chronographed that 90gr. 2F load? I'm thinking it is only making perhaps, 1,450fps. At that, with a zero at 100yds. it should only be about 2 1/2" high at 25.  Unless the
vel. is very much lower, your trajectory doesn't quite add up. With this load, a zero at 50yards would be almost 8" low at 100.
I would suggest some more range time with your rifle/sight combination.

[Roger B]

I appreciate  all the information & ideas, guys. Im going to make a front sight like Taylor uses & head back to the bench.
Roger

[D. Taylor Sapergia]

Roger, no matter what the range is, I always place the tip of the front sight in the centre of the bull/target.  To get centre impact at longer ranges, I simply lower the rear sight in relation to the front, ie:  hold front sight above the level rear sight.  With my old Jaeger .60 cal., I had to use the entire front sight down to the barrel above the rear sight notch for a hundred yard strike.  But it worked fantastically, and I was deadly with that rifle out to 200 yards.

[alacran]

What I have found if I sight in a rifle to shoot center at 100 yards, it will shoot center or close to center at 25 yards. It will shoot high at 50.
My GRRF works barreled Hawken wass sighted in at 100 yards of crossticks with 100 grains of Goex 2f. It shoots respectable groups with that load. It shoots about 5 inches high at 50 yards, and about dead on at 25 yards with a center of mass hold.

[Not English]

Roger, I shoot my 54 with 80gr of FFFg. It has a folding leaf rear sight. With the sight folded down and using and using the base sight, it is dead  on at 35Yds. With the small leaf folded up, it is dead on at 100yds. I don't subscribe to the changing your load for distance practice. It is a hunting gun and as such, there is no time to load according to distance when hunting. Just a bit of odd info. I have never worked up a load for this rifle. The first time out it shot tight groups at 35 yds. offhand by several different people and no one thought it was worth working up a load. It may well shoot better with a different load, but I'm happy with it's performance.

[Daryl]

Roger, I shoot my 54 with 80gr of FFFg. It has a folding leaf rear sight. With the sight folded down and using and using the base sight, it is dead  on at 35Yds. With the small leaf folded up, it is dead on at 100yds. I don't subscribe to the changing your load for distance practice. It is a hunting gun and as such, there is no time to load according to distance when hunting. Just a bit of odd info. I have never worked up a load for this rifle. The first time out it shot tight groups at 35 yds. offhand by several different people and no one thought it was worth working up a load. It may well shoot better with a different load, but I'm happy with it's performance.

That is the way my 100yard (folding sight) works as well.  I also have 2 others, for 150 and 200yards when using my hunting load.
With the light plinking load of 3drams to 85gr, that I use on trails, the sights zero at 50, 100 and 150.

[Jeff Murray]

Daryl's estimate of muzzle velocity for that load and ball is likely pretty close.  It may be a little slower depending on barrel length.  Using 1400 fps for muzzle velocity, you will get around 2-3 inches of drop at 50 yards and 12-13 inches of drop at 100 yards.   Your ball is probably cruising along at less that 1000 fps at 100 yards.  It drops pretty fast at that speed and is also more subject to wind drift.  A lot of options have been suggested.  The best one might depend on whether you use your rifle primarily for hunting or target/novelty shooting.  Higher velocities reduce both drop and drift at range.  I find it easier (better sight picture) to hold low for closer shots  than trying to hold high for longer shots at uncertain ranges.  At 1400 fps muzzle velocity, the difference in bullet drop between a 75 yard shot and a 100 yard shot is around 6 inches, and between 100 and  a 125 yard shot is around 8 inches.  That is a lot of SWAG when hunting.   

[Daryl]

Forsyth wrote about a 13 bore rifle he once had, that with a load that would not strip in it's very fast twist, the rifle was next to useless for hunting as it had a 13" of trajectory over a distance 100yards.
As he noted, how do you hold a fine sighting, when having that much elevation - the gun has no point blank range at all. Where do you hold on a charging bear, hog or deer? deer?
I prefer to have a long point blank range, wherein I do not have to think about holding high or low, over a normal hunting distance, which around here would run from 50 to 125yards or so.
Thus, if the ball is no more than 3" above, nor below the line of sight, the ball will always hit inside that 6" killing zone and no allowance for trajectory needs be taken.
With the hunting load in my rifle giving 1,550fps, this is the trajectory and why I load it as I do, for hunting.

[alacran]

Forsyth wrote about a 13 bore rifle he once had, that with a load that would not strip in it's very fast twist, the rifle was next to useless for hunting as it had a 13" of trajectory over a distance 100yards.
As he noted, how do you hold a fine sighting, when having that much elevation - the gun has no point blank range at all. Where do you hold on a charging bear, hog or deer? deer?
I prefer to have a long point blank range, wherein I do not have to think about holding high or low, over a normal hunting distance, which around here would run from 50 to 125yards or so.
Thus, if the ball is no more than 3" above, nor below the line of sight, the ball will always hit inside that 6" killing zone and no allowance for trajectory needs be taken.
With the hunting load in my rifle giving 1,550fps, this is the trajectory and why I load it as I do, for hunting.

That is why I sight in my hunting loads to shoot center  at 100 yards.