Lets settle it once and for all...
 

...whats the verdict on using PRB's with a 1/48 twist? Some say you'll never get a decent grouping, others say that statement is a myth... shoot the round balls! I'm new to the blackpowder game and recently bought a TC Firestorm. Just hopin' for some direction from some experienced fellas. Thanks!

Depends on the rifle, caliber and what you consider decent groups...

Both of my flintlocks are deep cut rifling, not the shallow button rifling found on factory rifles...The .40 is a 1-48 twist and the .54 is a 1-72 twist...Both will keep all shots inside an inch at 50 yards...Both are very tolerant of changes in powder charges, elevation may vary a bit but not windage...That's where the deep rifling helps...

The Hawken Brothers used a 1-48 twist, but their's was cut as well...

I have worked up loads for some of my buddies in the past with factory rifles and the 1-48 twist...I was able to attain hunting accuracy but I wouldn't classify them as having great target or competition accuracy...

Ok, thanks for the input. How would I know how deep the rifling is cut? So far: 1pt for PRB's...anyone else got any input? I realize that it's gonna take some trial and error on my part to find the best load, and I plan to go through that process, but I also don't think it hurts to gather opinions from other more experienced guys...

The twist will vary with the caliber:
Twist = 150 X D2/L
Where:
D = bullet diameter in inches
L= bullet length in inches
150 = a constant
This is called the Greenhil formula and the constant changes at 2800 FPS to 180
for practical use you need to understand that with a round ball the ideal twist for a 54 is about 1 in 80 and the ideal twist for a 50 is about 1 in 70 for hunting loads and to get the best trajectory. Will a 1 in 48 shoot accurate in both? The answer is yes but with a reduced powder load of about 90 to 110 gr some have had to go down to 85gr this will work fine for target to 100 yds but for hunting I prefer the correct twist and a max load that will shoot good. Will a 85 gr load take a deer? Yes but he will usually run farther with a 50 with a 54 you still have a quite a bit of impact or shock or foot pounds of energy just not as much.

lemoyne

Thanks Lee I totally agree and have been trying to get a reply in but not having any luck with replies...

I've got some maxi-balls and plan on grabbin' some PRB's. Guess I'm in for some experimentin'! Thanks for all the input so far, lookin' forward to any other opinions that might be out there too...:guiness:

It's really about RPMs. Round balls need less RPMs to stabilize than bullets which are longer than their diameter. Since the twist rate is not variable without buying another barrel, the other way to control RPM is to vary the velocity of the projectile. Reducing the powder charge slows both the velocity and the rate of spin. Unfortunately for the hunter, energy falls off dramatically as velocity is reduced. If you try conicals, you have control over velocity (powder charge) and bullet length (weight) to achieve the ideal combination of energy and accuracy. Have fun experimenting.

T/C 1-48 rifles normally shoot patched roundball real well. I shoot a lot of 1-48 twist and while I proved with open sights I am not a great shot, but for most shooting I do, with that twist I can do a real good job. Also I found that T/C likes powder so do not be shy with the horn.

Way back when, when PA started their primitive season you could only use flinters and PRBs. Most of us used T/C Hawkens, a couple had Renegades and even fewer had Lyman GP Rifles. The Lymans tended to shoot the PRBs a bit better with their 1:60 twist then the T/Cs. But the T/Cs with the 1:48 twist held their own. If I remember correctly, I used to use .015" patches and a .490 RB with a charge of 100 gro of FFFg.

Both my 54cal and my 58cal are 1-48" twist and they love roundballs even with heavy powder charges.

Sharp Shooter

Does that apply @ 100 yards?

ive gotten excellent groups with 1:48 twist along with patched round balls.

A 1-48 is a versatile twist, it will do all kinds of projectiles, I have shot PRB sabot and conical with good enough accuracy for hunting. Of course any thing that is made to be versatile is not going to be the very best in all situations. It is good enough to be what most people like the best. Part of the difference is if you us some of the old methods for determining how much powder you want, to me using the guns my grandfather or I made a charge of 130 gr was not unusual in commercially made guns you should go by what the manufacturer puts in the manual as the material is not always of the very best quality, and the parts are not hand fitted and have "tolerances".
Also people that have not made there own from scratch and proof tested them have a different scale of what a heavy or light charge is, ton me a charge under 90 gr is a light charge and a charge over 120 is a heavy charge. The point of max efficiency changes with different powders and with the different bullet weights, very few of us a looking for the most efficient powder load, the load of max efficiency is never the highest velocity but is the point at which you get the most feet per second per grain of powder. Due to age how long we have been in the sport and past experience we tend to use different terms while meaning the same thing. I have noticed my self and mike do this every once in a while. Lee

What I would like to know going back to the original question and adding this... which twist rate will provide you the best hunting accuracy @100 yards or beyond?

50/75 yards is not a problem at all with a 1/48. But for myself, shooting a 1/48 going to 100 yards really opens the pattern up, especially when shot with what i would call a hunting load charge 80/90 grains in a 50 cal.

Another question... What size of group might an average shooter expect using open sights @ 100 yards with a PRB?

Sabotloader...I assume you are talking about deer calibers...As I mentioned in my first post, if a fellow wants a round ball barrel he is best served with deep cut rifling (.015-.018 deep) vs button rifling (.006 deep)...This will better grip the patch...

I could look up the rifling twist on Getz's or Rice's website but as I remember these are standard twists for round ball barrels...

.40 caliber...1-48
.45 and .50 caliber 1-66
.54 caliber 1-72

I know my little .40 shoots good with from 25-70grs of Goex FFF and the .54 does well with from 50-120grs of FFF...That's a pretty wide spread and I vary the charge for game being persued...I believe this is one of the big differences between factory and custom round ball barrels...The factory rifles I have shot had a "sweet" spot where they shot a certain powder charge well...In other words, custom barrels aren't as picky as powder charges and ball/patch combinations...

nchawkeye

OK so let me ask the re-pharse the question again....

What I would like to know going back to the original question and adding this... which twist rate will provide you the best deer hunting accuracy @100 yards or beyond? Adding another stipulation - using the shallow grooved bore of the time.

50/75 yards is not a problem at all with a 1/48. But for myself, shooting a 1/48 going to 100 yards really opens the pattern up, especially when shot with what i would call a hunting load charge 80/90 grains in a 50 cal.

Another question... What size of group might an average shooter expect using open sights @ 100 yards with a PRB?

I understand the deeper grooves are probably superior to todays shallow grooves, but in a production gun available today I think we are limited to shallow grooves...

I assume that my firestorm has a shallow-grooved barrel, and I forgot to mention its a .50 cal. All of that to say, sabotloader and I probably have similar set-ups, and I'd love to hear answers to his two questions...

Got this answer back on another forum....

I prefer a slow twist deep grove rifling for prb , I have a tc hawkins in 54 cal , wiff the factory barrel ( 1-48 twist ) it does not have deep grove rifleing , it shoots a concal bullet good but for prb I get 2 to 3 inch groups at 50 yards , so I replaced the barrel wiff a green mountain barrel 1-72 inch twist deep groove rifleing and all I can say wow , it shoots a one hole group at 50 yards and at a 100 yards I can get 2 to 3 inch groups or better. I use 90 grains of ffg , last fall I shot a doe wiff it using prb, she was 100 yards from me and I drop her using one shot in the head , for me I like a slow twist barrel , others mite not but it works for me and very pleased wiff the groups I can get. Dats my 2 cents

A prb is all I shoot from my Traditions Deer Hunter .54 cal. It does the job out to 100 yards.:barmy:It has a 1:48 twist.

A couple of more repies that i have gotten...

To me it still looks like the slower twist would be the a more consistently accurate barrel. And while using the 1/48 you may need to reduce the charge to gain long distance accuracy. I feel very comfortable with a 1/48 out to 75, even shooting an animal @ 100 - although, i know I could do it but I could never actually feel good shooting that far with a PRB - not enough experiance + plus my accuracy concerns.

Mike the slow twist with the heavy load is better, it will group better at long range because with a heavy load the ball is moving faster and so there is less time for wind and gravity to move it around. Best for deer at long range, well my opinion is base on having tried all common caliber at 177 yds working on the Hawken and Mountain man shoots at friendship using a Hawken with a 1-89 twist and 130 gr of RS I got a 19 inch string. considering two of the shots were off hand I thought that was about as good as I could do. I have taken two deer and one bear [over 300#] all one shot kills at over 177yds and none of them went 20 yds after being hit. A lot of people sell a PRB short. I do not use a 50 at that range or a 58 the 50 is affected to much by the wind and the 58 has a rainbow trajectory that don't even compare to the 54. They are all good guns at the range they work best at but with PRB only the 54 shines at over 150yds. Of course this is all my opinion but years of long rage competition and 60 years of hunting are what formed that opinion. Lee

Good stuff...thanks all!