Rates-of-twist

[Old Hawkeye]

I'm not sure what you intend the scope of this claim to be. In "free air" (i.e., unconstrained in something like a cartridge or a barrel), smokeless powder burns relatively slowly compared to black powder. But who cares about that unless you just like to watch stuff burn in open air? What would clear some of these things up is reference to a well-documented and supported burn rate table which describe the precise conditions under which measurements were made. Otherwise, it's just "he said/he said". We do know that when confined, smokeless powder exhibits a much steeper pressure curve and rate of burn than when burning freely in air, and a much steeper pressure curve than does black powder (at least most smokeless powders do). Basically, when B.P. is compared to smokeless in a gun barrel, it is much faster burning -- at least at and beyond a certain point in its combustion, and this is precisely why it can produce such higher muzzle velocities.

Also, I'm quite confused by the claim that "If the power [sic] burn is slowed down a bit it produces more gas ...". I guess by this you mean that if the burn rate is decreased, then more complete combustion (=> more gas) will result.. But this would be so only if there is sufficient time for the lower combustion rate to result in sufficiently more complete combustion before the bullet is out of the barrel. For a given barrel length, it's far from obvious that lowering the powder burn rate would in fact result in more gas, and so result in a higher muzzle velocity for the bullet. Is this just a thought experiment that you're putting out? Or can you point to any data supporting it -- and precisely what the variables are that might affect the results? Or have I just missed the point?

I don't think there is a point. Best to take Mark Twain's advice on this one & let it go.

 

[doubleset]

I don't think there is a point. Best to take Mark Twain's advice on this one & let it go.

He had lots of advice. I'll just pick one of my favorites and go with it.

 

[BlazingIron]

quote:Originally posted by charlief:
I heard somewhere that a 1-in-66 is best for round balls and the 1-in-48 , for example are better for sabots.Muzzleloading bullets do require a faster twist (1-in-48) because of the longer bearing surface and greater mass.
The round ball has "LESS" mass and bearing surface, thus requires a slower rate of twist, say 1-in-66 or greater.
I have seen riflings as slow as 1-in-98 twist before...

These rate of twist will also set your min/max loads too... Too fast of a twist can strip a round ball from it's patch before leaving the barrel, resulting in a major pressure leak.

Just like those "HIGH POWERED RIFLES", bullet stabilization is directly related to the riflings, and if a 30.06

is rifled for a 180 grain bullet or better, then 110 grain bullets will not be as stabile and it will pattern all over the target.

Bottom line, trial and error will tell, you can shoot round balls in fast twist barrels, just not as accurately as with a slower twist.
The same goes for shooting maxi-balls and sabots from a round ball barrel, it will work, just not as good as a faster rate of twist barrel.

Somewhere, there is a "HAPPY MEDIUM" just waiting to be found.

A HAPPY MEDIUM:

 

[hanshi]

No one has yet to come out and say it so I suppose I will. The big distinction that separates black with smokeless has to do with the fact that smokeless is a progressively burning powder while black isn't a progressively burning powder to any real extent. Pour a trail of each and light them up. The BP fizzes along pretty quickly while the smokeless burns quietly and not nearly as fast as BP. Then put both in their respective barrels. In this case as the pressure from primer ignites the smokeless pressure starts to build very, very quickly. As the pressure rockets higher the smokeless burn rate increases exponentially sending the pressure many times higher than black. OTOH the BP burns, as has been mentioned, at higher pressure given the fact the burn is contained in the breech. So the BP firing a prb may range from 5,000 psi to 9,000 psi with a good load. But the smokeless gives pressures of 18,000 psi to well over 50,000 psi. BP has a very limited velocity range and quickly reaches the peak of old, sedate smokeless rounds and can go no further. Smokeless raises pressure in to stratospheric levels of 55,000 to more than 60,000 psi.

This is the limit of my understanding on the subject at least.

 

[Okie Hog]

Way back when smokeless powder was replacing black powder in cartridges, it was found that lead bullets often failed to obturate and fill the rifling grooves when smokeless powder was used. It was found that black powder gets up to maximum pressure much faster than smokeless powder.

Old timers referred to this phenomenon as "the boot of the black".

Black Powder Pressure Curves & Bullet Obturation (texas-mac.com)

 

[LME]

A HAPPY MEDIUM:
View attachment 136044

You got it!

 

[Coinneach]

Well , read both pages on this thread , and come to the conclusion that (1) this is the best darn site of this type out here , (2) during my reading i was distressed , repressed , and impressed by what i read , & , (3) guess i will just keep makin' smoke with what works for me . BTW , had a 1in32 barrel gun once , and it was a much better shooter with conicals than i was . Did not like the looks of it , so, traded for a "surf rod and reel" , and think i got the better end of that trade !! Keep makin' smoke fella's , it is all good !!!

I'm still waiting to find out what Black Powder flavoured Ice cream tastes like......

 

[M. De Land]

No one has yet to come out and say it so I suppose I will. The big distinction that separates black with smokeless has to do with the fact that smokeless is a progressively burning powder while black isn't a progressively burning powder to any real extent. Pour a trail of each and light them up. The BP fizzes along pretty quickly while the smokeless burns quietly and not nearly as fast as BP. Then put both in their respective barrels. In this case as the pressure from primer ignites the smokeless pressure starts to build very, very quickly. As the pressure rockets higher the smokeless burn rate increases exponentially sending the pressure many times higher than black. OTOH the BP burns, as has been mentioned, at higher pressure given the fact the burn is contained in the breech. So the BP firing a prb may range from 5,000 psi to 9,000 psi with a good load. But the smokeless gives pressures of 18,000 psi to well over 50,000 psi. BP has a very limited velocity range and quickly reaches the peak of old, sedate smokeless rounds and can go no further. Smokeless raises pressure in to stratospheric levels of 55,000 to more than 60,000 psi.

This is the limit of my understanding on the subject at least.

An interesting conversation. I think Mann had some interesting things he discovered about BP combustion and bullet bump up.. I think he found it was still burning up bore several inches and it did not all burn at once. Also I've read that BP only converts about 55 percent of the solid to gas which is why there is so much fouling.
I remember reading about the tests at Sandy Hook . They used a .45 caliber rifle , a 500 grain round nose bullet with a 19 or 20 inch pitch if memory serves and were recovering the bullets at 2 miles from the sand. They were all still hitting point on and apparently stabile as most will tumble at long range once they go wobbly..