What kind of accuracy can I expect from a 40-70 sharps bottleneck?  Can this be a one minute round out to 200 yards? Is there a significance difference in performance and accuracy between that and the 40-70 sharps straight?   

I am considering this round for a new barrel on an old Remington rolling block which I recently got ahold of.  I welcome any advice anyone might want to share.   

Thanks.

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Hello, Whistlepigger.  I have a .40-70 Str. in an Axtel long-range Sharps 77'  I also have a .40-70 BN in a Lone Star long-range Rolling Block.  Both have 34" brls.  With the straight, using H4895, I can put 10 in one ragged hole at 100yds.  The B.N. I am still working on..It has put them in close..11/4 to 11/2" at 100 but not like the straight.  I haven't tried black in either yet.  I am using  300-350gr. bullets in the Axtel because of it's regulation 10lb. it tends to hurt with heaver.  The Lone Star is built for Silhouette so it is heaver & I can stand a bit more lead.  The Axtel started shooting groups like that from day one, which isn.t normal..for me anyway..the .40-70BN gives me something to work towards.  Best of luck!

Lots of opinions on twist rates. I think 18 - 22 is closer to the traditional twist rate for old rifles. The 16 twist became popular in the late 1980s

My 40/50 SS has a 22 inch twist. I shoot 400 grain bullets out to 600 with no problem. Straight BP. My 40/65s with 18 inch twist shoot good out to 1000 yards. 

I used to shoot 540 grain bullets in an original hiwall in 45/70. It had a 20 inch twist. It had to be duplex loaded to stabilize out the the rams. 

Lots of different ideas on twists. 

               Joe.

This is my take on twist......... I want a twist rate with what ever bullet and twist that I shoot to be just stable enough that it doesn't tip when it goes through the target (or object). Anything else is a waste and over stabilized, there for the centrifugal force has acted on it more than need be and the imperfections (no, we never cast imperfect bullets, I know) aren't magnified as much at the lower RPM. Temperature and altitude have a effect so, you take that into account, also but, it's not a big factor.

Frank

One thing I haven't heard anyone say is deliberately matching your velocity to the twist. This is a very real thing in round ball guns.  With those, the opposite is true when it comes to twists in target vs hunting guns. For instance, most of the newer barrels, from Colerain and other companies, have fast twists (1:48 for .40, 1:60 for 45, 1:66 for .50) in order to allow lighter, slower loads for less recoil in target work. With the exception of one .40 collerain barrel, my rifles all have slower twists which allow higher velocity. (My three older guns--one .40, one .38 and one .35--all have 1:56.) In my .40 Colleran (if I spell it differently every time I might get it right) I get excellent accuracy with 42 grains of powder. On the other hand, a good friend of mine has a .40 flintlock with a slow twist of 1:72, and he is running 70 grains.  I cannot begin to shoot that fast, or my accuracy goes all over the map. (Yes, I weigh my balls.) This gives him a decided advantage in wind and distance.

So does this hold true with the bullet guns--does a fast twist barrel benefit from reduced velocity? If they do, I would think there would be a point of no return when it comes to more twist and longer bullets, because air time would be increased. Of course, a ball is a ball, where as bullets are all different shapes, each requiring a different twist (and speed?). I think I understand you to say, Dave, that the faster twists which you prefer allow a bullet with a higher coefficient, and this allows you higher velocity for the same weight?

Honestly, there is not a thing I do with a center fire that cannot be better done with a flintlock--until I pass the 100 yard mark.  Since most of my hunting is well under that, hitting mostly comes down to the gun that holds the best. So, the only real reason for a cartridge gun for me at this point is power and distance. That is why I first thought of the .50 over my .45-100 and then backed off to the little .40.   

I ran some calculations on the Don Miller formula for stabilization to show the effects of twist, temperature and velocity. My base line was a .321 bullet, 195 gr, 1.035 long, 1000 fps with a stabilization factor of 1.4. All these other combinations have the same 1.4 stabilization factor.

Bullet     FPS   Twist    Temp
1.035    1000    16        70
1.085    1000    15        70
1.085    1475    16        70

Temperature effect:

1.035    1125    16        50
1.035      850    16      100 

In this application, it takes 475 fps to make up for 1 inch of twist and 275 fps to make up for 50 degrees of temperature.
Most of us have shot at temperatures above 100 and below 50 so, it's something to watch out for if your close to stabilization on your twist rate..

I miss spoke (fancy way of saying I lied) about the way that temperature effects stability in my above post. I was thinking about how velocity goes up with temperature. Two different things.

Frank