Conical or PRB IN .50 1 in 24 twist?

[SDSmlf]

@BlazingIron, I have some items and information I can send you that you might find helpful with your load testing. Send me a PM if interested.

 

[towgunner11h]

I can say one thing for sure....it's more than rifling that's twisted around here.

Anybody have a Goody's?

I'm getting a headache..........

Well, I'm going to eat some crow here and admit I was wrong. I was correct in that RB can be very accurate in a fast twist, but I was not taking into account that it must usually be with a low or reduced powder charge, making it much less useful.

 

[deermanok]

I have a pistol (unmentionable)
fast twist, 1/28, I believe.
It actually shoots a ball quite well with a 60 grain (V) charge of 3f Swiss.

 

[Grenadier1758]

@deermanok, you have a reduced charge in the pistol, so the velocity of the ball is considerably slower than a ball shot in a rifle. With the slower velocity and the higher rate of twist the ball from the pistol will have a similar revolutions per minute to stabilize the ball as the ball shot from a rifle. Very different things to consider when shooting a pistol or shooting a rifle.

 

[deerstalkert]

@deermanok, you have a reduced charge in the pistol, so the velocity of the ball is considerably slower than a ball shot in a rifle. With the slower velocity and the higher rate of twist the ball from the pistol will have a similar revolutions per minute to stabilize the ball as the ball shot from a rifle. Very different things to consider when shooting a pistol or shooting a rifle.

let's. now we have RPI, RPM"s, TWI's. i am getting ptsd!

 

[new2bp]

Twist needed to stabilize is dependent on length of bullet in relation to bore diameter AND velocity A certain number of RPMS must be achieved

Too much twist and velocity and you either hit weird physics (Coriolis effect) or in the case of small light unmentionable bullets they can be ripped apart

 

[The Appalachian]

I'll repeat, it's all about the physics.

A patched roundball has a somewhat different set of rules than other projectiles. Being a sphere, the PRB has an extremely minimal contact surface with the bore compared to other types of bullets. It relies on a thickness of cloth material to engage the rifling and impart a rotational spin.

The issue is, there is a high probability that a fast twist will strip the patching and fail to impart an adequate rotational spin on the ball. So to compensate for that physics in standard production barrels you can reduce the charge down to a velocity that prevents the patch from being stripped, or, you can hammer a much tighter patch down the bore. Both of which aren't of great use to most shooters. In my own world those conditions contribute to the attitude that it "won't work".

Someone somewhere decided that 1:48 in shallow groove production barrels is a good enough compromise for folks who want to shoot PRB and conicals/sabots out of the same barrel. It provides just enough decent accuracy with hunting charge weights of powder.

The strictly PRB guys stick with the much slower twist rates because of the ease of loading with a thinner patch, and probably less need to swab between shots, while achieving enough accuracy.

When you switch to a projectile that's not a patched roundball other rules of physics take hold. Now you have exponentially more surface area in contact with the bore. The standard twist rate calculations come in to play. The main rule there is guided by the length of the bullet, which dictates it's bearing surface in the rifling, in relation to the bore diameter. I'm not going to deep dive into comparisons between such things as a 22 cal bore and a 45/70 bore, and whatever in between, but the general rule is, the longer bullet needs a faster twist to achieve a gyroscopic rotational spin to stabalize flight.

This is just a quick overview of my personal knowledge of the subject having spent considerable time in my half century + fooling with 18th/19th century weapons, a stable of fat bore lever guns, and a few extended long range centerfire rifles that I've used in competitions. I am a huge fan of accuracy no matter what I'm shooting so it behooves me to have at least a working knowledge of it.

There are hundreds if not thousands of volumes of published data that provide the details of internal and external ballistics available for anyone looking to understand it better.

 

[Maven]

All, I have a .50cal. unmentionable rifle with a 1:28 twist Green Mtn. bbl. and receiver sight (Williams). To answer the OP's questions:

Will it shoot RB's accurately, say at 50 yd.? Yes, but with no more than 50gr. FFg.

Will it shoot conicals accurately at the same distance? Generally yes, but it depends on how well the conceal fits your bore. E.g., T/C Maxi-Balls, which I cast, fit my bore perfectly and are accurate with up to 80gr. [loose] FFg. Others, such as the Lee Target Minie, not so much unless paper patched and even then they aren't as accurate as the Maxi-Ball.

What about saboted cast bullets? It depends on the sabot itself and the cast bullet (design and weight) you're trying to shoot. E.g., I've tried MMP sabots with 405gr. cast bullets (sized to .459") and they were just OK, but a ~245gr. semi-wadcutter design, which I also cast, went into a large hole @ 50 yd. (Btw, this was either the Lyman #429421 or the RCBS version of it.) The problem with sabots is twofold. Finding the one that fits your bbl. and dealing with the plastic fouling they leave behind.

Hope this helps!

 

[cynthialee]

As you can see there is a lot folks want to say on this topic.

Twist rate, depth of rifling, length of barrel, size of charge, weight of the bullet....all of it makes a difference in things.

Your gun will shoot heavy conicals very well with standard charges, just need to find the right combo of conical size (there are a number of options) and powder charge. That is a good barrel for longer range hunting if you can deal with the recoil of a heavy conical and a stout powder charge.

Your gun will also shoot a PRB reasonably well, typically with a smaller powder charge and a good tight fitting patch and ball combo. With PRB your range will be a little limited, but if you hunt forest or scrub this is not a concern.

In either case it is going to take you range time and a note book to figure it all out. While we can make suggestions, each gun has its own 'right load' for any particular projectile.

 

[Relic shooter]

Bear in mind that Jäger Rifles had a twist rate of one turn in the barrel length. These were short barreled rifles with barrels of 24 to 30" in length. When Pedersoli marketed their Jäger rifle, it has a twist rate of 1 in 24" and can achieve reasonable round ball accuracy and take chamois from one Alpine ridge to the next.

Happy to see you bring fast-twist rifling for PRB up, you might get hammered with debates on this subject. Before reacting to what rate of twist is correct folks need to do some research first.
Your correct in stating that it's typical for original short barreled Jaegers to have one-turn in the barrel length.
I've been collecting, hunting & competing with original big bore Jaegers for around 50 years. I favored Jaegers because of their lighter weight due to swamped barrels, balance & suburb accuracy.
My favorite Jaeger is in .70 cal is a fairly plain somewhat military styled Danish rifle that was built by I.C. Haugaard in Kiobehaven. He was a master armorer for the crown. This rifle consistently produced cloverleaf groups at 50 yards for me with just 80 grains of 2F when I do my part & only ran a cleaning patch down after 15 or so shots to maintain easy loading.
The reason these vintage fast twist barrels shoot so well with round balls is because the rifling in most Jaeger barrels are a minimum of .012 deep. If the correct sized RB is used in combination with a thick high density lubed patch I've yet to not get consistently excellent accuracy.
The rifling in most modern mass production ML barrels are very shallow at around .006 deep. If a RB is not patched extremely tight in fast twist shallow rifled barrels with high density cotton lubed patches they will skip-riflings, shred patches & produce poor groups with hunting loads.

 

[SDSmlf]

Happy to see you bring fast-twist rifling for PRB up, you might get hammered with debates on this subject. Before reacting to what rate of twist is correct folks need to do some research first.
Your correct in stating that it's typical for original short barreled Jaegers to have one-turn in the barrel length.
I've been collecting, hunting & competing with original big bore Jaegers for around 50 years. I favored Jaegers because of their lighter weight due to swamped barrels, balance & suburb accuracy.
My favorite Jaeger is in .70 cal is a fairly plain somewhat military styled Danish rifle that was built by I.C. Haugaard in Kiobehaven. He was a master armorer for the crown. This rifle consistently produced cloverleaf groups at 50 yards for me with just 80 grains of 2F when I do my part & only ran a cleaning patch down after 15 or so shots to maintain easy loading.
The reason these vintage fast twist barrels shoot so well with round balls is because the rifling in most Jaeger barrels are a minimum of .012 deep. If the correct sized RB is used in combination with a thick high density lubed patch I've yet to not get consistently excellent accuracy.
The rifling in most modern mass production ML barrels are very shallow at around .006 deep. If a RB is not patched extremely tight in fast twist shallow rifled barrels with high density cotton lubed patches they will skip-riflings, shred patches & produce poor groups with hunting loads.

We have been told by experts the OP didn’t ask about Jaegers, so any information or comparisons to original Jaegers is irrelevant for this topic. Reported as too difficult to load or some such thing. Though my experiences shooting Jaegers has been similar to yours and I agree with you.

 

[52Bore]

My original EM Reilly Sporting rifle, 50 cal, 1:20 twist shot very well with a 500gr PP conical over 85gr Swiss 2F at 300 yds - 2-3moa. Groups started opening when shooting at 5-600.
Bullet blew a gaping hole thru a Buck at 130yds.

 

[The Appalachian]

We have been told by experts the OP didn’t ask about Jaegers, so any information or comparisons to original Jaegers is irrelevant for this topic. Reported as too difficult to load or some such thing. Though my experiences shooting Jaegers has been similar to yours and I agree with you.

You should be able to deduce that yourself, with original Jaegers having rifling twice and deep as modern production barrels.

Apples to oranges........

 

[SDSmlf]

The issue is, there is a high probability that a fast twist will strip the patching and fail to impart an adequate rotational spin on the ball. So to compensate for that physics in standard production barrels you can reduce the charge down to a velocity that prevents the patch from being stripped, or, you can hammer a much tighter patch down the bore. Both of which aren't of great use to most shooters. In my own world those conditions contribute to the attitude that it "won't work".

You should be able to deduce that yourself, with original Jaegers having rifling twice and deep as modern production barrels.

Apples to oranges........

Agree, depth of rifling is critical, whether shooting a roundball (typically deeper) or conical (typically shallow), but your point has till now just been twist rate. Kind of late to add depth of rifling, as I brought it up earlier in the thread and you chose to ignore it in your comments until now.

Jaegers had what we would call fast twist with their one twist per barrel length guns that were made and used for roundballs with their deeper grooves.

 

[The Appalachian]

Agree, depth of rifling is critical, whether shooting a roundball (typically deeper) or conical (typically shallow), but your point has till now just been twist rate. Kind of late to add depth of rifling, as I brought it up earlier in the thread and you chose to ignore it in your comments until now.

No sir, but since you seem to want to argue this to death.......

My initial response and all of my responses after that were in the context of the OP's modern production barrel, and his situation with it. Not some off the wall irrelevance that didn't apply to him, or his rifle. You sir, went down the wrong rabbit hole, and were told about it.

Exactly how does it help the OP by telling him that fast twist deep groove original Jaegers would shoot PRB just fine when his problem is with a fast twist shallow groove Pedersoli Hawken?

It doesn't.......

 

[Rock Home Isle]

I have a .50 cal Ped. Traditional Hawken Hunter with a 1 in 24 twist Will I be able to get any decent accuracy with PRB or am I gonna have to use conicals?

Fast twist barrels are more along the lines of conical projectiles, they are ideal for conicals. That doesn’t mean you can’t use it to shoot PRBs, the problem with shooting PRBs in fast twist barrels is that the contact point between the ball and the rifling doesn‘t have a lot of real estate…and the ball strips out of the rifling and accuracy is lost.

So if you want to shoot PRBs out of a fast twist barrel…you’ll be shooting low velocity target type of loads, and even then…accuracy may not be as high as you’d like it to be.

 

[Ninering62]

Well, I'm going to eat some crow here and admit I was wrong. I was correct in that RB can be very accurate in a fast twist, but I was not taking into account that it must usually be with a low or reduced powder charge, making it much less useful.

Ummm..... Crow - its whats for supper at towgunners. Good on ya sir! I've had that meal a time or two in my life too. It ain't ever tasty, but it is good for us all.

 

[Ninering62]

Fast twist barrels are more along the lines of conical projectiles, they are ideal for conicals. That doesn’t mean you can’t use it to shoot PRBs, the problem with shooting PRBs in fast twist barrels is that the contact point between the ball and the rifling doesn‘t have a lot of real estate…and the ball strips out of the rifling and accuracy is lost.

So if you want to shoot PRBs out of a fast twist barrel…you’ll be shooting low velocity target type of loads, and even then…accuracy may not be as high as you’d like it to be.

RHI - NAILS IT!

 

[Red Owl]

There might be a little overkill on the issue of twist. I have a 1:32 CVA mountain stalker and thought I'd try a PRB. I had to drop the charge way down so this is for fun at the target range but at 50 yards it does fine.

 

[Ninering62]

There might be a little overkill on the issue of twist. I have a 1:32 CVA mountain stalker and thought I'd try a PRB. I had to drop the charge way down so this is for fun at the target range but at 50 yards it does fine.

You just confirmed what Rock Home Isle said.