grrw-ca rifles and pistols
03-04-2016, 04:35 AM
#51
Giant Nontypical
Join Date: Feb 2011
Location: Colorado
Posts: 9,557
Muley read this very slowly so you can comprehend. Regardless of twist rate a projectile will continue that rotation after it leaves the barrel. The barrel length has nothing to do with it. If that same 10" barrel had a 1:70 twist rate and you loaded it with say an 80 grain charge it would stabilize the ball the same as if it was fired out of a rifle. Lets make this so even you can understand. If you have two twist rates - a 1:60 and a 1:20 the projectile from the 1:20 will be rotating 3 times faster than the 1:60. At 10' from the muzzle the projectile from the 1:60 will have made 2 revolutions while the one from the 1:20 will have made 6. All the twist does is start the process. It doesn't matter if the barrel is 4" or 40".
Like I have surmised or assume. The faster twist in a pistol may only be necessary due to the lower velocity because of the lighter charge in order to stabilize the ball. That is the only logical explaination. Otherwise one could use a 1:20 twist in a rifle with an 80 grain or more charge and a PRB with good accuracy. But we all know that is not the case.
Like I have surmised or assume. The faster twist in a pistol may only be necessary due to the lower velocity because of the lighter charge in order to stabilize the ball. That is the only logical explaination. Otherwise one could use a 1:20 twist in a rifle with an 80 grain or more charge and a PRB with good accuracy. But we all know that is not the case.
Tell us wise one. Why do you think pistols have a faster twist?
As for the stripping. A PRB won't strip the rifling if it's a deep groove. Faster twist barrels are normally made for conicals/sabots with shallow rifling. If a PRB is shot too fast in those barrels the grooves are too shallow for the PRB to hold on to. A PRB in a deep groove barrel won't strip even if it's on the fast side.
Once again I tried to help by answering a question, and get told i'm wrong and insulted by forum know it alls. This won't happen for much longer.
03-04-2016, 06:03 AM
#52
Boone & Crockett
Join Date: Jan 2004
Location: Eastern PA
Posts: 12,747
Your quote: Wrong!! Since we're talking about a 10" barrel in a pistol with a much slower fps than the 35" barrel with a faster fps. They both turn the ball 1/2 turn in the barrel. At 100yds which one do you think will turn the ball more times? How about 25yds?
Answer: Velocity has nothing to do with the number of turns. The rate of twist determines that. Velocity only determines how long it will take for the projectile to get there.
25 yards (900") 100 yards (3600")
1:20 45 rotations 180 rotations
1:70 12.86 rotations 51.43 rotations
Pete there is no insulting by me only by you. - Please look at what both you and I are saying. We are both correct. You are saying that in a 35" barrel with a 1:70 twist the projectile will make 1/2 turn and in a 10" barrel with a 1:20 twist the projectile will also make 1/2 turn. You are correct. However they are not turning at the same rate.
Out of a 35" barrel that ball from the 1:20 twist will have made almost 2 full turns whereas if the ball was shot out of a 10" barrel with a 1:70 twist the ball will only rotate less than 1/4 turn.
And if you read my post and comprehend what I am saying my thoughts are that the faster twist is required due to the lesser velocity from the lighter charge.
As for the effects of twist rate in a barrel I don't think I can explain it any simpler. Barrel length has absolutely nothing to do with twist rate. The twist rate of the rifling in the barrel, whether the barrel is short or long, determines how fast the projectile will rotate. Maybe someone else can try to explain it better.
Answer: Velocity has nothing to do with the number of turns. The rate of twist determines that. Velocity only determines how long it will take for the projectile to get there.
25 yards (900") 100 yards (3600")
1:20 45 rotations 180 rotations
1:70 12.86 rotations 51.43 rotations
Pete there is no insulting by me only by you. - Please look at what both you and I are saying. We are both correct. You are saying that in a 35" barrel with a 1:70 twist the projectile will make 1/2 turn and in a 10" barrel with a 1:20 twist the projectile will also make 1/2 turn. You are correct. However they are not turning at the same rate.
Out of a 35" barrel that ball from the 1:20 twist will have made almost 2 full turns whereas if the ball was shot out of a 10" barrel with a 1:70 twist the ball will only rotate less than 1/4 turn.
And if you read my post and comprehend what I am saying my thoughts are that the faster twist is required due to the lesser velocity from the lighter charge.
As for the effects of twist rate in a barrel I don't think I can explain it any simpler. Barrel length has absolutely nothing to do with twist rate. The twist rate of the rifling in the barrel, whether the barrel is short or long, determines how fast the projectile will rotate. Maybe someone else can try to explain it better.
Last edited by bronko22000; 03-04-2016 at 06:56 AM.
03-04-2016, 07:09 AM
#53
Giant Nontypical
Join Date: Feb 2011
Location: Colorado
Posts: 9,557
I didn't say barrel length changes the twist rate. I was trying to explain why pistol barrels need a faster twist. Since that's how they come it seems to be correct.
The velocity difference is a given and I didn't think it needed to be mentioned. You didn't understand why pistols come with a faster twist. I tried to explain why.
btw Speaking of twist and a bit off topic, but when I talked to Green Mountain about their barrels I was told they worked a long time to come up with the sweet spot for twist rate and barrel length. The 32" barrel with a 1-70 twist was the best combo they came up with. Along with the dimensions of the rifling. I know the one I had was the sweetest shooting PRB barrel i've ever tried.
The velocity difference is a given and I didn't think it needed to be mentioned. You didn't understand why pistols come with a faster twist. I tried to explain why.
btw Speaking of twist and a bit off topic, but when I talked to Green Mountain about their barrels I was told they worked a long time to come up with the sweet spot for twist rate and barrel length. The 32" barrel with a 1-70 twist was the best combo they came up with. Along with the dimensions of the rifling. I know the one I had was the sweetest shooting PRB barrel i've ever tried.
03-04-2016, 03:11 PM
#54
Boone & Crockett
Join Date: Jan 2004
Location: Eastern PA
Posts: 12,747
I'm sorry Muley. I had no idea you can't comprehend what I am trying to say. Of course barrel length doesn't change twist rate. You asked a question about how many twist a bullet would make at 25 and 100 yards. I responded with the two different twist rates you mentioned. (1:20 and 1:70)
And as it was pointed out by you and muzzlestuffer I have come to believe the faster twist is necessary because of the velocity of the lighter charge. (less velocity requires more twist).
So don't get our panties in a knot just because I am answering a question that you asked me.
And as it was pointed out by you and muzzlestuffer I have come to believe the faster twist is necessary because of the velocity of the lighter charge. (less velocity requires more twist).
So don't get our panties in a knot just because I am answering a question that you asked me.
03-04-2016, 08:33 PM
#55
Nontypical Buck
Join Date: Oct 2006
Location: Penns Woods
Posts: 1,628
Well maybe I'm wrong but, from everything I've ever heard or read, the reason why they put a faster twist in pistol barrels was to impart the required spin of the projectile albeit bullet or ball as it was only traveling a short distance before leaving the barrel.
It made sense to me because otherwise you may as well have a smoothbore if the bullet/ball is only going to begin to turn with a slow twist before exiting the barrel.
Just my .02!
BPS
It made sense to me because otherwise you may as well have a smoothbore if the bullet/ball is only going to begin to turn with a slow twist before exiting the barrel.
Just my .02!
BPS
03-05-2016, 04:10 AM
#56
Boone & Crockett
Join Date: Jan 2004
Location: Eastern PA
Posts: 12,747
I was doing some looking around and found this FAQ on Dixie Gunworks site.
So therein lies the reason for the fast twist in a ML pistol. Lower velocity due to light charges like I've been saying after a couple responses to my original question. The faster twist is necessary to stabilize the ball at these lower speeds. It has nothing at all to do with barrel length.
- How does the barrel rifling affect the performance of the muzzleloader?
So therein lies the reason for the fast twist in a ML pistol. Lower velocity due to light charges like I've been saying after a couple responses to my original question. The faster twist is necessary to stabilize the ball at these lower speeds. It has nothing at all to do with barrel length.
03-05-2016, 04:56 AM
#58
Spike
Join Date: Feb 2016
Posts: 12
I read in one of Sam Fadala's books year ago, that it is the "revolutions per second" (RPS) that stabilizes a bullet/ball. Therefore, it is a combination of velocity and twist rate that stabilize. This is why modern bullet may shoot fine to 400 yards but begin to tumble/key hole as it slows down at 500 yards. It is still spinning but forward velocity is slowing way down. Different for every bullet. You have likely seen a thrown football do this exact same thing.
Velocity is affected by powder type, powder charge, weight of bullet, length of barrel, and maybe even a few more things.
Twist rate is affected only by twist.
Since a pistol barrel is very short it is hard to get much as velocity. So to stabilize a given bullet you have to increase the rate of twist for that short barrel to stabilize that bullet/PRB.
That's about how Fadala explained it. And he is correct.
And yes, you can push a PRB or conical so hard that it "strips" off the rifling. It is a fact. Bronco22000 makes some very good points.
Velocity is affected by powder type, powder charge, weight of bullet, length of barrel, and maybe even a few more things.
Twist rate is affected only by twist.
Since a pistol barrel is very short it is hard to get much as velocity. So to stabilize a given bullet you have to increase the rate of twist for that short barrel to stabilize that bullet/PRB.
That's about how Fadala explained it. And he is correct.
And yes, you can push a PRB or conical so hard that it "strips" off the rifling. It is a fact. Bronco22000 makes some very good points.
Last edited by Old Smoke; 03-05-2016 at 05:03 AM.
03-05-2016, 05:20 AM
#59
Boone & Crockett
Join Date: Jan 2004
Location: Eastern PA
Posts: 12,747
Thank you OldSmoke. Lower velocity requires faster twist for stabilization. That is what I've been trying to say but it just doesn't sink in to some.
Last edited by bronko22000; 03-05-2016 at 05:22 AM.