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Projectile specific gravity

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: FighterAce » Sun Oct 17, 2010 12:23 pm

SpudFarm wrote:
What do you think about this? Length is 30mm, caliber is still 1.27mm.

Does not make sence..


Sorry.. typo fixed :lol: again

Your formulas are all theory... did anyone actually use one to get a specific twist rate and actually stabilize the projectile?
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Unread postAuthor: Lockednloaded » Sun Oct 17, 2010 12:24 pm

have you though of using hollow tail rounds that will be more stable and fly straighter?
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Unread postAuthor: POLAND_SPUD » Sun Oct 17, 2010 12:32 pm

I don't know we he insists on spin stabilization...?
Good (heavy) drag stabilized ammo would be a lot more practical
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Unread postAuthor: al-xg » Sun Oct 17, 2010 12:32 pm

When making the tool, that flat zigzag cut into the cylinder does end up producing the right grooves.

I've found that approximation to be close enough, with my manufacturing capabilities but then again they are pretty poor.

Image
As long as it ends up looking something like that.

I've fired various bullets of different shapes and length from the same barrel and results don't to vary too much, some more accurate testing would be required to optimise things, but at least it doesn't go drastically wrong.

Edit: mmm yeah that only works with very low pitches...
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Last edited by al-xg on Sun Oct 17, 2010 12:51 pm, edited 1 time in total.
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Unread postAuthor: FighterAce » Sun Oct 17, 2010 12:38 pm

Lockednloaded wrote:have you though of using hollow tail rounds that will be more stable and fly straighter?


Hollow tail plaster or concrete? I think thats a prime candidate for blowing up

POLAND_SPUD wrote:I don't know we he insists on spin stabilization...?
Good (heavy) drag stabilized ammo would be a lot more practical


Practical ≠ Precision

I gotta move on... I've been using rocks till now, let me move on to bows n arrows! :lol:
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Unread postAuthor: POLAND_SPUD » Sun Oct 17, 2010 12:59 pm

There is a reason why ammo looks the way it looks. If you don't want to use lead (I don't know why? you don't have to cast it) then what do you expect? You want to make ammo out of plaster that would be better than .408 CheyTac?
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Unread postAuthor: dewey-1 » Sun Oct 17, 2010 1:03 pm

FighterAce wrote:
Lockednloaded wrote:have you though of using hollow tail rounds that will be more stable and fly straighter?


Hollow tail plaster or concrete? I think thats a prime candidate for blowing up

POLAND_SPUD wrote:I don't know we he insists on spin stabilization...?
Good (heavy) drag stabilized ammo would be a lot more practical


Practical ≠ Precision

I gotta move on... I've been using rocks till now, let me move on to bows n arrows! :lol:


Use the following drawing as guide for dimensions and ratios of caliber to nose radius and projectile length.

Have you considered brass tubing as the hollow base and use epoxy and a lead or steel ball as the tip?

add link: http://www.amazon.com/Brass-Seamless-Ro ... 488&sr=1-8

Why attempt rifling first. Get a good projectile that is drag stabilized first, check it for accuracy and range and then proceed to your rifling dream!
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Unread postAuthor: al-xg » Sun Oct 17, 2010 1:32 pm

And either way, you don't need crazy sniper bullets to use a rifled barrel. I'd start with the barrel and then just experiment with bullet shapes later.
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Unread postAuthor: FighterAce » Sun Oct 17, 2010 3:43 pm

dewey-1 wrote:Why attempt rifling first. Get a good projectile that is drag stabilized first, check it for accuracy and range and then proceed to your rifling dream!


Been there, done it. I feel like a noob that just discovered homemade pneumatics and is being guided how to start :roll:

Maybe I'm typing in a different language without knowing it? I have no idea why people dont read before they post.

I will use lead... when I get a job and start earning money... witch will be in about 3 years...
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Unread postAuthor: dewey-1 » Sun Oct 17, 2010 4:24 pm

FighterAce wrote:Maybe I'm typing in a different language without knowing it? I have no idea why people dont read before they post.



Well maybe you should also read your own posts to verify which language you are using.

First it was 7.7mm length, then 1.27mm caliber.

I give you a drawing for caliber to length ratios to answer your question and you do not even appreciate that.
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Unread postAuthor: Ragnarok » Sun Oct 17, 2010 6:25 pm

FighterAce wrote:Practical ≠ Precision

But at the other end of the scale they're not mutually exclusive. Bear in mind, the drag stabilised M829A3 round from the Rheinmetall 120mm tank gun has accuracy that would better many rifles.

Feel free to go with rifling if you really want, but drag stabilisation can be just as accurate - sometimes more so.
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 18, 2010 4:18 am

Ragnarok wrote:But at the other end of the scale they're not mutually exclusive. Bear in mind, the drag stabilised M829A3 round from the Rheinmetall 120mm tank gun has accuracy that would better many rifles


I was about to mention that, modern smoothbore tank guns can reliably hit targets several kilometres away.
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Unread postAuthor: FighterAce » Mon Oct 18, 2010 5:47 am

dewey-1 wrote:Well maybe you should also read your own posts to verify which language you are using.

First it was 7.7mm length, then 1.27mm caliber.

I give you a drawing for caliber to length ratios to answer your question and you do not even appreciate that.


Thats the price I have to pay... converting from imperial to metric units... and then back. No wonder I make mistakes... but thank you for pointing them out to me.

And thank you for the drawing.. I didnt even take a look at it yesterday so how could I appreciate it?


jackssmirkingrevenge wrote:
Ragnarok wrote:But at the other end of the scale they're not mutually exclusive. Bear in mind, the drag stabilised M829A3 round from the Rheinmetall 120mm tank gun has accuracy that would better many rifles


I was about to mention that, modern smoothbore tank guns can reliably hit targets several kilometres away.


Thats quite a feat of engineering and aerodynamics... I didnt graduate either so how could I make something like that?

About the rifling angle formula... whos right? Ragnarok or al-xg or both?
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 18, 2010 6:11 am

FighterAce wrote:Thats quite a feat of engineering and aerodynamics... I didnt graduate either so how could I make something like that?


Take a look at this HEAT round:

Image

Not exactly a sleek engineering marvel, but fired from a smoothbore barrel it is accurate out to at least 2,000 metres.

Besides, you don't have to go for fins, a hollow tail as on these foster type slugs works just as well:

Image

If you can cast that beautiful spitzer shape then these should be a doddle :)

Have a look at whatthe box'o'truth has to say on the subject, in the case of this type of slug rifling makes very little difference to accuracy (and this comparison was hardly fair as the smoothbore test shotgun only had iron sights while the rifled shotgun had a scope).
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Last edited by jackssmirkingrevenge on Mon Oct 18, 2010 6:13 am, edited 1 time in total.
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Unread postAuthor: al-xg » Mon Oct 18, 2010 6:12 am

The one I posted only approximates it, if the twist rate is low (the case of most rifling). Steeper rifling moves away from that straight line look.

I haven't tried Rag's formula yet, it should be quite easy to verify though.
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