Lets settle it once and for all...
03-29-2010, 01:05 PM
#1
Spike
Thread Starter
Join Date: Mar 2010
Location: Pennsylvania
Posts: 19
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!
Last edited by gobblegrunter; 03-29-2010 at 01:07 PM.
03-29-2010, 01:15 PM
#2
Giant Nontypical
Join Date: Nov 2004
Posts: 5,425
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...
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...
03-29-2010, 02:02 PM
#3
Spike
Thread Starter
Join Date: Mar 2010
Location: Pennsylvania
Posts: 19
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...
03-29-2010, 02:35 PM
#4
Giant Nontypical
Join Date: Nov 2005
Posts: 6,585
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.
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.
03-29-2010, 04:31 PM
#6
Spike
Thread Starter
Join Date: Mar 2010
Location: Pennsylvania
Posts: 19
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...
Last edited by gobblegrunter; 03-29-2010 at 04:34 PM.
03-29-2010, 04:54 PM
#7
Fork Horn
Join Date: Mar 2008
Location: Kitchener Ontario
Posts: 245
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.
03-29-2010, 04:54 PM
#8
Dominant Buck
Join Date: Feb 2003
Location: Wisconsin
Posts: 21,193
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.
03-29-2010, 05:36 PM
#9
Boone & Crockett
Join Date: Jan 2004
Location: Eastern PA
Posts: 12,745
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.
