Help understanding ballistics

[Dutchy Rodell]

Assumptions:    '1858 Remmie Cap and Ball firing a 454 round ball - 20 grains of 777
                      Gun is mounted on a bench rest and aimed at center of bull's eye
                      No wind
                      Target distance is 7 yards
                      Ball hits 6" below center of target
                   

Question:         If for the second shot, the load is increased to 25 grains, all other thing remaining the same - will the ball impact   
                      above or below the previous point of impact?

[w44wcf]

Chances are that it will impact either at the same place or slightly lower since the ball, at a higher velocity, will exit the barrel sooner .......when the barrel is lower in recoil.

w44wcf

[Dick Dastardly]

Yup, that's the same reason a heavier bullet with the same conditions will likely high higher.  It'll be slower, so the gun barrel will be rising more when the bullet exits.

Seems backwards.

DD-DLoS

[Adirondack Jack]

The rhyme to remember is "lighter prints lower, slower prints higher."

at 15 yards, my .45 vaqs.  print to POA with 200s at 650, 250s at 750, and 310s at 1275.

Note how much faster ya gotta shoot the heavier stuff to get em to exit the muzzle at the same point in the recoil arc.  Now the 200 is a puffball, the 250 is modest, and the 310 a monster.  if I slow any of em down, they will shoot high, and the heavier ones will shoot REAAALLLLLLY high.

Speed em up and they shoot really low, especially the lightest ones.  (a 150 at 1200 shoots real low   )

[hellgate]

My experience has been light bullets shoot lower than heavier bullets regardless of the powder (smokeless) charge. I was trying to get both a light bullet (113 & 115gr) load that shot to the same POI as my 158gr bullets. No matter what charges I used the heavier bullet always printed higher than the lighter bullet. If memory serves, whether the light & heavy bullets were going fast or slow they still printed heavy high and light low. These were cast lead bullets in the .357 mag.

Using bulky BP or BP subs, there is the weight of the powder to be expelled that can add some weight to the "projectile" (powder and bullet). You can put more powder under a lighter bullet but it wont likely change things a whole lot.

[Dutchy Rodell]

Thanks for your comments.  If I understand you correctly changing from 20 grains to 15 grains will cause my round ball to hit higher because it is going slower.       Dutchy

[hellgate]

Dutchy,
Shoot that gun with the load you want to use and then file the front sight down to where you are hitting where you are aiming. Also you will want to shoot the gun freehand either duelist style or with two hands before messing with the sight. You might be surprised as to where it hits when not using a rest. If it is a Pietta there is a lot of front sight to file. I have had to do it with all my Ubertis and formerly owned Pietta Remingtons except the Euroarms guns (3). They all shoot high.

If you shoot a 200gr conical it will shoot higher. That was the case with all my Remingtons.

[Griff]

What hellgate said.  Sandbags can differ greatly from off-hand.

[Dutchy Rodell]

Actually I have been shooting off hand.  I just used the example of a bench rest so that it would be perfectly clear that the only thing that changes in the number of grains of powder.  Off hand I shoot low with 20 grains.  If I can I would prefer to find a load the will allow me to hit point of aim rather than filing my sights.   Dutchy

[Griff]

If you were shooting real BP, I'd suggest a significant increase in charge.  According to the Hodgdon's website, 20 grains represents 536fps.  25grs represents 763fps, that's might be significant enough to raise the point of aim.  Sometimes, if you're shooting a very light load, recoil is so slight that you're shooting abnormally low.  If you then bump up the charge into the full charge area, your recoil increases raising the point of aim.

Certainly worth a try.  It's not like it's overly robust for a 1858 Remmie.

[Silver Creek Slim]

I don't know much about 777, but using 30grs of FFFg Goex under a ball in my Piettas gets me as close to POA as I will ever get.

Slim

[Sir Charles deMouton-Black]

Hellgate has it right;

1.  Don't alter fixed sights until after you have determined, and tested with a field position, your service load.

2.  Move backsight in the direction you want the group to move.

3.  Move frontsight TOWARDS the error.

4.  For pistols, generally (*Always?), the heavier the projectile the higher the rounds will strike. It is a matter of changes in jump from recoil and "barrel time" cancelling each other out.  Velocity changes do not affect the placement of the group, weight does.

PS;  *In my experience it is "Always".  I f you can document anything different I would be delighted to hear about it.

[Delmonico]

I'll add this also since many don't think about it either, a different shooter with a different hold and even different eyes will also often change point of impact.  YThis is true with both rifles and handguns and can really show up on a scoped rifle. 

[Driftwood Johnson]

Howdy

We've been around and around the block on this one. Does a faster bullet get out of the barrel before the muzzle lifts as high? Does the heavier recoil from the higher powder charge lift the muzzle high enough to raise the point of impact before the bullet escapes?

My own personal experience is that with identical bullets, in the same gun, heavier powder charges raise the point of impact every time. Regardless of how fast the bullet is getting out of the barrel, when I increase the powder charge, recoil has been increased enough to raise the point of impact.  That has been my experience.

[john boy]

Gun is mounted on a bench rest and aimed at center of bull's eye

Dutchy, to simulate shooting offhand using a rest (sand bags) ... hold the revolver Traditional 2 handed style and place the back of one hand on top of the sandbag.  This will allow the muzzle to rise

[Adirondack Jack]

Howdy

We've been around and around the block on this one. Does a faster bullet get out of the barrel before the muzzle lifts as high? Does the heavier recoil from the higher powder charge lift the muzzle high enough to raise the point of impact before the bullet escapes?

My own personal experience is that with identical bullets, in the same gun, heavier powder charges raise the point of impact every time. Regardless of how fast the bullet is getting out of the barrel, when I increase the powder charge, recoil has been increased enough to raise the point of impact.  That has been my experience.

You might see some of that with mellow BP loadings, where you are actually resisting recoil effectively with the softest loads.

Step it on up and it ain't so, at least in my experience.

My 5.5 inch vaqueros have not had  the sights cut, and from the box will shoot to POA with 250s at 750.

I've shot 310 (nominal, might be a hair more) LEE GC bullets at 1250 or so and guess where they print?  same as the 250s at 750.

I also shoot a 200 at 650, and yep, same POI/POA alignment.  Speed that 200 up to 1000 fps, its waaaay low.

Slow the 200 to 580, it shoots high.  Slow a 310 down to 700 FPS it shoots high.