PRB ballistics puzzle

[Pymahunter1]

This is my first year hunting a flintlock, shooting a 54 cal Renegade with stock sights. Load I am using is 80 grains 2f Goex, .530 Hornady ball, TC pre-lubed pillow ticking patch (can't remember if that's .018" or .020" thickness). I tried sighting in at 50 yards and started a good 4 inches high, lowered the rear sight as far as it would go and was still ~2 inches high. I put a target at 30 yards and found that I was dead on at that range. I ran some numbers through this calculator (1500 fps MV, 1" sight height):
ctmuzzleloaders.com/ctml_experiments/rbballistics/web_apps/rb_ballistics.html

And find that the ball should dropping somewhat between 30 and 50 yards. Any ideas what is going on here?

 

[Saxtonyoung]

I'm assuming your thinking that your sighted in for 30 yards and it should drop at 50. In reality your probably sighted in closer to 100 yards. Your bullet is going to hit bullseye at 2 different distances and will be still rising or falling in between. There is no such thing as a flat shooting bullet, all bullets start dropping after leaving the barrel and most people are thinking thier barrel or I should say the bore is level but it reality your muzzle end is higher than the breech end of the bore that cuases your trajectory to looks like an arc.

 

[sdporter]

The law of gravity is just that, a law. As soon as something is released, it falls, doesn’t matter how fast or slow its forward momentum is taking it, it falls at the same rate. The faster it’s traveling, the less it falls at different distances, but it’s still headed to the ground at the same rate, as far as inches per second. I’d move out to 80-100 yards and see what’s going on. You can plot a trajectory from there. My guess is that most factory sights on a MZ are gonna be set up for around a 100 yard zero. Saxton is correct, your bullet (or ball) is going to go through two different line of sight points in its trajectory because the sights are higher than the bore center. @Idaholewis might chime in here on the range of factory sights, but I’m betting you’re not gonna hit a zero at 50 yards without a 6 o’clock hold. If you’re trying for a 50 yard zero, you’re just gonna have to learn how much lower you have to hold to get your target, or get a shorter front bead.

 

[sdporter]

With my 30.06 they claim it crosses through zero at roughly 25 and 200 yards shooting 150 grain factory Ammo traveling roughly 2800 FPS. I always sight in 2” high at 100 and this gives me a dead center hold on deer from zero to about 300.

 

[Pymahunter1]

Thank you for your replies. I plug the variables into the ballistics calculator with a 100 yd zero and it does indicate a rise in elevation of ~2 inches between 30 and 50 yards. I was hoping to be sighted in at 50 yards since I have difficulty using the iron sights any further than that. I can put this in a different thread if needed, but how does one remove the front sight on a Renegade?

 

[Saxtonyoung]

What are you hunting that your focus is on 50 yards ? If know it 2" high at 50 yards and your out of sight adjustment you can aim 2" lower than you want to hit but if your hunting deer and your looking to hit vitals you have an 8- 10" area to hit so being super precise isn't as big a deal as might think.

 

[deermanok]

If you were shooting competition, you'd probably want to be more precise but for hunting, 2 inches high at 50 yards isn't a bad thing imo. I think your front sight is in a dovetail slot. If so, putting the barrel in a vise and with a punch and hammer, you could tap the sight right out, if you really want to change it. If it was me, I wouldn't mess with it.

 

[Pymahunter1]

I only plan to hunt whitetail with this gun. I agree that this is good enough precision for hunting deer, however I really dislike the sight. I won't change it out this year, but I might in the future. I read some discussion on the forum recently about some fiber optic options appropriate for hunting in low light conditions.

One more query...if I wanted to lower the point of aim, wouldn't I want the front sight to be higher? Thanks again for your input!

 

[Saxtonyoung]

Yes you need a taller front sight.

 

[sdporter]

I mis-spoke. Yes you want a taller front sight

 

[snapbang]

If you really dont like the sights you could try cutting (filing) the v on the back sight a little deeper. Take a triangular file and give it a try. A little removal will go a long way.

 

[451whitworth]

Pymahunter1,
Did you actually chrony your load at 1500 fps or are you just going off some published data that says it should be that? The reason I'm asking is I find Goex 2Fg to be very weak velocity wise especially with the limited resistance of a PRB, and the data in the old T/C owner's manual and Lyman Black powder Handbook overly optimistic. I will share some of my data from my .54 Renegade as an example. All loads shot with .018" pillow ticking and home cast .530" round ball:
120gr Goex 2Fg = 1525 fps
120gr Goex 3Fg = 1592 fps
105gr Swiss 2Fg = 1756 fps
105gr OE 2Fg = 1729 fps

 

[snapbang]

I never chronied my .50 RB but assumed with 100 grains of powder I should be 1900fps or so. I was never that technical with my sidelock.

 

[Pymahunter1]

Pymahunter1,
Did you actually chrony your load at 1500 fps or are you just going off some published data that says it should be that? The reason I'm asking is I find Goex 2Fg to be very weak velocity wise especially with the limited resistance of a PRB, and the data in the old T/C owner's manual and Lyman Black powder Handbook overly optimistic. I will share some of my data from my .54 Renegade as an example. All loads shot with .018" pillow ticking and home cast .530" round ball:
120gr Goex 2Fg = 1525 fps
120gr Goex 3Fg = 1592 fps
105gr Swiss 2Fg = 1756 fps
105gr OE 2Fg = 1729 fps

I don’t have access to a chrono. I was using data from TC’s handbook and knocking it down a bit as I had read they are overly optimistic with their numbers. They had 1654 fps for that load (80 grains of black). I hoped to be in the ballpark, but it doesn’t seem like it! Sure wish I could find some Swiss locally!

 

[451whitworth]

I don’t have access to a chrono. I was using data from TC’s handbook and knocking it down a bit as I had read they are overly optimistic with their numbers. They had 1654 fps for that load (80 grains of black). I hoped to be in the ballpark, but it doesn’t seem like it! Sure wish I could find some Swiss locally!

I have a feeling that your speed is more in the 1300-1400 fps range. This is an interesting topic because if you think of all the Hawken/Renegades that T/C made, production figures probably approach a million units. Running out of sight adjustment with the issued sights is not something that you hear about often if at all with those rifles. Maybe I've not been paying attention. Anyone else had this happen? Flint rifles usually have lower velocity compared to cap locks because of the larger vent hole, sometimes 100 fps. I would try upping the powder charge to see what happens. Barrel time and recoil change impact points. You could see if you could bum a couple 70gr. charges of Triple 7 loose powder off some one also. Since you have black powder you could load 10gr. first then dump the 70gr. T7 on top and check your impact as an experiment. I have a Green Mnt. IBS .36 cal drop in barrel for my T/C Hawken. That rifle will hit 2000 fps and beyond with that little round ball. I had to put a .600" tall front sight on to zero it.

 

[Renegadehunter]

This is my first year hunting a flintlock, shooting a 54 cal Renegade with stock sights. Load I am using is 80 grains 2f Goex, .530 Hornady ball, TC pre-lubed pillow ticking patch (can't remember if that's .018" or .020" thickness). I tried sighting in at 50 yards and started a good 4 inches high, lowered the rear sight as far as it would go and was still ~2 inches high. I put a target at 30 yards and found that I was dead on at that range. I ran some numbers through this calculator (1500 fps MV, 1" sight height):
ctmuzzleloaders.com/ctml_experiments/rbballistics/web_apps/rb_ballistics.html

And find that the ball should dropping somewhat between 30 and 50 yards. Any ideas what is going on here?

As you have found out, what is going on is the ball is still "rising" between 30 and 50. You have more like a 75-80 yard zero right now. A bit odd that you have run out of sight adjustment. You never know what others could have done, if you bought it used you might make sure the previous owner didn't shim under the rear sight for some reason. Long shot but worth checking.

IMO the easiest way to be able to get an exact 50 yard zero, since your rear sight is bottomed out, is to swap out your front sight. You will want to measure the height of your current sight, from top of the flat (barrel) to the tip of the sight, and then order a bit taller sight as a replacement.
Many times a replacement dovetail sight will be a bit big for your rifle's dovetail slot, so be prepared to file a bit off the bottom of your replacement sight's dovetail. Other than removing any possible burrs you never want to file on your rifle's dovetail slot. Always adjust the sight to the rifle, not the rifle to the sight.
My Williams sight was quite a bit too big, I had to file a decent amount off of it before it would go clear to the center of my renegade's dovetail slot. I just laid a flat file flat on my workbench and then made passes across it with the sight. Check fit often of course, and of course check fit before starting to file on it.
Many dovetail slots are tapered. As you look down the barrel as if you were going to shoot, my renegade's dovetail slot is meant for the sight to be removed left to right. So drive the old sight out to the right and install the new sight from the right side back to the left.

 

[Pymahunter1]

I have a feeling that your speed is more in the 1300-1400 fps range. This is an interesting topic because if you think of all the Hawken/Renegades that T/C made, production figures probably approach a million units. Running out of sight adjustment with the issued sights is not something that you hear about often if at all with those rifles. Maybe I've not been paying attention. Anyone else had this happen? Flint rifles usually have lower velocity compared to cap locks because of the larger vent hole, sometimes 100 fps. I would try upping the powder charge to see what happens. Barrel time and recoil change impact points. You could see if you could bum a couple 70gr. charges of Triple 7 loose powder off some one also. Since you have black powder you could load 10gr. first then dump the 70gr. T7 on top and check your impact as an experiment. I have a Green Mnt. IBS .36 cal drop in barrel for my T/C Hawken. That rifle will hit 2000 fps and beyond with that little round ball. I had to put a .600" tall front sight on to zero it.

I'm looking forward to playing with a variety of loads with this rifle after the season is done. I;ve only shot 70 and 80 grain loads of black thus far...I started low as I had read that accuracy can suffer with larger loads with PRB's in 1 in 48 twist. duplexing the loads is a good idea, I have 777 on hand. I also plan on experimenting with a variety of patch thicknesses and lube types, I just need to find range time!

As you have found out, what is going on is the ball is still "rising" between 30 and 50. You have more like a 75-80 yard zero right now. A bit odd that you have run out of sight adjustment. You never know what others could have done, if you bought it used you might make sure the previous owner didn't shim under the rear sight for some reason. Long shot but worth checking.

IMO the easiest way to be able to get an exact 50 yard zero, since your rear sight is bottomed out, is to swap out your front sight. You will want to measure the height of your current sight, from top of the flat (barrel) to the tip of the sight, and then order a bit taller sight as a replacement.
Many times a replacement dovetail sight will be a bit big for your rifle's dovetail slot, so be prepared to file a bit off the bottom of your replacement sight's dovetail. Other than removing any possible burrs you never want to file on your rifle's dovetail slot. Always adjust the sight to the rifle, not the rifle to the sight.
My Williams sight was quite a bit too big, I had to file a decent amount off of it before it would go clear to the center of my renegade's dovetail slot. I just laid a flat file flat on my workbench and then made passes across it with the sight. Check fit often of course, and of course check fit before starting to file on it.
Many dovetail slots are tapered. As you look down the barrel as if you were going to shoot, my renegade's dovetail slot is meant for the sight to be removed left to right. So drive the old sight out to the right and install the new sight from the right side back to the left.

This is all very helpful! I did check and I'm certain there is no shim under the rear sight:

The front sight measures around 0.36 inches tall (from top of barrel). Any guess as to how tall a replacement would need to be to get me on at 50?

Thanks to all for your help with this.

 

[Saxtonyoung]

That's an older style of sight and probably my least favorite of the TC sights. With you sight you line the top of the front sight with the top of rear sight.

I'm a bigger fan of a bead front sight and a v notch rear sight. The bottom of the bead sits on the v giving you a better sight picture. With this particular rear sight bottomed out the bottom of v is .325 and the bottom of the front bead is .400. I believe these dimensions would give you the advantage of sighting at shorter ranges.

 

[Renegadehunter]

The front sight measures around 0.36 inches tall (from top of barrel). Any guess as to how tall a replacement would need to be to get me on at 50?

Thanks to all for your help with this.

Here is a link for calculating sight height.
Rifle Sight Height Calculator – Mark Elliott (markelliottva.com)

I have no idea how accurate the calculator might actually be, but you can check its accuracy by plugging in your current setup and impact info.
Just winging it, I'd say a .450" height sight should give you a decent range of adjustment for common muzzle loader hunting distances. I just ordered a different F.O. sight for my renegade and went with a .500" height. My current set up has a front sight height of .375 (3/8) and I would be all but bottomed out if I wanted a 50 yard zero, my rear sight is adjusted quite low to have a 75 yard zero. I'll be happy if .500 will still allow me to have a 75 yard zero even if the rear sight ends up maxed out. Guess I'll see.

 

[Chick]

That's an older style of sight and probably my least favorite of the TC sights. With you sight you line the top of the front sight with the top of rear sight.

I'm a bigger fan of a bead front sight and a v notch rear sight. The bottom of the bead sits on the v giving you a better sight picture. With this particular rear sight bottomed out the bottom of v is .325 and the bottom of the front bead is .400. I believe these dimensions would give you the advantage of sighting at shorter ranges.

Both of those types of sights are horrible.