.50-70 Rainbow

Black powder rifles and pistols, reloading black powder, and other information. The smoky stuff.

Re: .50-70 Rainbow

Post by <<Genesis93>> » 14 Mar 2017, 9:20 am

in2anity wrote:
<<Genesis93>> wrote:
in2anity wrote:
<<Genesis93>> wrote:BC of 0.1 sounds a bit low... closer to a brick... made of foam..


Not really, think, 22 subs are 0.12 Besides isn't BC relative to MV anyway? (Lower the mv the lower the BC)


BC has nothing at all to do with MV.... it is a function of the 'slipperyness' or inverse of aero drag, relative to a 'standard projectile'...


Then how do you explain this:

https://www.sierrabullets.com/store/pro ... -170-gr-FN

(just as a example) scroll down to where it stipulates the BCs based on MV ranges. Not that I'm mathematical enough to really argue, I don't think it's quite as simple as you make it out to be. I might be wrong...


Yes... for a given bullet the BC will vary to a degree.... I was referring to your comment;

Not really, think, 22 subs are 0.12 Besides isn't BC relative to MV anyway? (Lower the mv the lower the BC)


lower mv = lower BC is absolutely not the case...as a generalisation...
If referring to specific projectiles and the slight variation over velocity - even your example has an increasing BC with reducing velocity....
<<Genesis93>>
Second Lieutenant
Second Lieutenant
 
Posts: 2191
-

Re: .50-70 Rainbow

Post by in2anity » 14 Mar 2017, 9:36 am

<<Genesis93>> wrote:
lower mv = lower BC is absolutely not the case...as a generalisation...
If referring to specific projectiles and the slight variation over velocity - even your example has an increasing BC with reducing velocity....


Yes agreed, my comment "(Lower the mv the lower the BC)" is not strictly true, sometimes they weirdly go up with lower MVs. I stand corrected here.

But my point is BCs are not constant for a given projectile (rather they change depending on MV), and I always found slow stubby RN/FN projectiles will have a markedly low BC (just like 22lr subs). Hence my (latest) estimation of 0.12 for OP. One thing is for almost certain, the BC for OP's particular projectile is definitely going to be closer to .2, nowhere near .3 territory
Last edited by in2anity on 14 Mar 2017, 7:01 pm, edited 1 time in total.
At what point does lack of maintenance become patina?
User avatar
in2anity
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 3048
New South Wales

Re: .50-70 Rainbow

Post by <<Genesis93>> » 14 Mar 2017, 10:09 am

As I said the 317 was iterated with the 1200fps... and the woodleigh 50cal RN was in the .2xx range (^ I said up there somewhere) ...

If the velocity is lowered to 1050 with the same drop, then the BC would be a lot higher than the 0.317 value...
<<Genesis93>>
Second Lieutenant
Second Lieutenant
 
Posts: 2191
-

Re: .50-70 Rainbow

Post by in2anity » 14 Mar 2017, 10:16 am

<<Genesis93>> wrote:If the velocity is lowered to 1050 with the same drop, then the BC would be a lot higher than the 0.317 value...


Fair enough, but given the MV, we'll have to agree to disagree on that one
At what point does lack of maintenance become patina?
User avatar
in2anity
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 3048
New South Wales

Re: .50-70 Rainbow

Post by Gamerancher » 14 Mar 2017, 3:55 pm

Okay, after doing some research, the Lyman 425gr .50 cal cast lead bullet has a B.C of .250, so I'd give Noiseys' 450gr a similar value. The only load data (actual, not assumed) I could find with measured velocities in .50-70 with blackpowder were with 70grains, not the 55gr load he describes. Those 70gr loads were measured at 1170fps with a 450gr Lyman bullet. So I go back to my original comment that I don't believe he's getting them out at 1200fps. I believe that a more conservative estimate of about 1050 fps would be a bit closer to what Noiseys' load is doing.
B.C's for big fat bullets at blackpowder velocities don't follow the trend that you would expect from long pointy supersonic jacketed small calibre bullets. Having a centre of gravity pretty close to the middle of the bullet that is about 3 x diameter in length gives about the best results for BC and hence stability.
Gravity acting on the bullet over time of flight is what gives you your bullet drop, lower velocity = longer time of flight = more drop.
I just ran it through the Hornady calculator online using 1000fps MV and got about a 21 yard bullet drop @ 600yards. Is that what we were after? :unknown:
User avatar
Gamerancher
Sergeant Major
Sergeant Major
 
Posts: 1596
New South Wales

Re: .50-70 Rainbow

Post by Noisydad » 14 Mar 2017, 5:17 pm

Sight height is .471" above the barrel.
I hold dead on at 200 yards.
There's still a few of Wile. E Coyote's ideas that I haven't tried yet.
User avatar
Noisydad
Warrant Officer C1
Warrant Officer C1
 
Posts: 1383
Victoria

Re: .50-70 Rainbow

Post by Gamerancher » 14 Mar 2017, 5:25 pm

What brand of powder are you using Noisey?
User avatar
Gamerancher
Sergeant Major
Sergeant Major
 
Posts: 1596
New South Wales

Re: .50-70 Rainbow

Post by in2anity » 14 Mar 2017, 7:16 pm

Gamerancher wrote:I just ran it through the Hornady calculator online using 1000fps MV and got about a 21 yard bullet drop @ 600yards. Is that what we were after? :unknown:


I too was fiddling with the Hornady calculator- which is what makes me think the BC might actually l be under .2 A lot of .50 cast projs online have a BC less that .2
At what point does lack of maintenance become patina?
User avatar
in2anity
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 3048
New South Wales

Re: .50-70 Rainbow

Post by Noisydad » 14 Mar 2017, 8:08 pm

Using Wano. Cant afford Swiss lol.
There's still a few of Wile. E Coyote's ideas that I haven't tried yet.
User avatar
Noisydad
Warrant Officer C1
Warrant Officer C1
 
Posts: 1383
Victoria

Re: .50-70 Rainbow

Post by Gamerancher » 15 Mar 2017, 8:08 am

Fair enough. In my experience, I get 10% more velocity out of Swiss Vs Wano for the same loading.
User avatar
Gamerancher
Sergeant Major
Sergeant Major
 
Posts: 1596
New South Wales

Re: .50-70 Rainbow

Post by Noisydad » 15 Mar 2017, 12:19 pm

Yeah I've heard that. Does it really burn cleaner? I figure that given its nearly twice the price I can put up with some cleaning.
There's still a few of Wile. E Coyote's ideas that I haven't tried yet.
User avatar
Noisydad
Warrant Officer C1
Warrant Officer C1
 
Posts: 1383
Victoria

Re: .50-70 Rainbow

Post by Gamerancher » 16 Mar 2017, 8:34 am

Definitely cleaner, especially your cases. I've also found that I can leave fired cases for up to a couple of weeks before cleaning, ( forgot about them after a large multi-gun shoot ). I've also been able to get that bit better accuracy out of the Swiss. Velocity S.D's down to single digits with Swiss compared to mid-teens to low 20's with Wano. That translates to less vertical dispersion which is what I need for silhouette and the long range. ( out to 1000yds )
User avatar
Gamerancher
Sergeant Major
Sergeant Major
 
Posts: 1596
New South Wales


Back to top
 
Return to Black powder shooting