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Author Topic: Testing round ball obturation theory. An invitation.  (Read 2163 times)

Offline Stormrider51

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Re: Testing round ball obturation theory. An invitation.
« Reply #30 on: May 09, 2011, 06:59:59 PM »
Quote from: "Captchee"
Stormride
again  even a lose fitting ball will expand .
  you can never get  the  acceleration needed  to produce the effect  because physically by striking your RR  you not even beginning to  replicate the force of  acceleration  obtained  by  the explosion.
 In fact what your doing is getting expansion by force  striking an object , not by propelling and object
 Lets see if I can explain this  better .
 Lets assume that the ball rides the pressure wave . IE  nothing is striking the ball , its accelerating .
 Lets say a  given test load  produces 1700 ft per second
1 mile =5280ft
 IE its traveling 1 mile in 3.10 sec
60 sec per minute  =19.35  miles  per min.
 60 min. per hour =1161mph

 Now lets  think of  the G’s that  imparts  onto an object  if it goes from 0 to 1161 mph in  1 /100000th of a sec ?
 Even if we accept  slower burn , its still accelerated to that speed , in less the 28 inches .
 The force of that acceleration alone  will cause expansion even  with no expansion taking place by the propelling force at all .

Amen to everything you said.  Plus, I think that since I was able to measure bullet upset with many hundreds times less pressure than what exists in a barrel during actual firing situations, there can't be much doubt that it does happen.  I think the data also shows that the greatest upset will happen when there is sufficient tightness to cause friction resistance.

John
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Offline Stormrider51

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Re: Testing round ball obturation theory. An invitation.
« Reply #31 on: May 09, 2011, 07:02:49 PM »
Quote from: "Gordon H.Kemp"
Stormrider51 at this point it seems all evidence , both mathamatically and pysica indicate that obturation is a fact and not just a theory , and so far no one has come forward with evidence to disprove these findings .
        There has been one factor left out of the test results  and that is the added resistance of the ball patch combo being forced against the spiral of the lands to begin rotation .
         Now this brings up another question ? We need to repeat these tests on how much obturation takes place in a smoothbore . ???
        I don"t know if its still available on the TMA archives but the last reports on BP behavior may be able to be pulled up . Bill Knight no doubt , has forgotten more about BP then most of us will ever know . I will copy off the tests by Ed Yard and Fadala and post them . It will take a while as I know less about computers then flying the space shuttle. :toast

Interesting that you should mention smoothbores.  You were spying and know that I got one in the mail today, right?  Anybody got a section of cut-off smoothie barrel?

John
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Offline R.M.

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Re: Testing round ball obturation theory. An invitation.
« Reply #32 on: May 09, 2011, 07:11:59 PM »
John, you could always lop off a couple of inches from that new gun.  :rotf
R.M.
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Offline Stormrider51

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Re: Testing round ball obturation theory. An invitation.
« Reply #33 on: May 09, 2011, 07:58:36 PM »
Quote from: "R.M."
John, you could always lop off a couple of inches from that new gun.  :rotf

Hmmmmmm......let me think about that for a moment....................................Nope.
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Offline FlintSteel

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Re: Testing round ball obturation theory. An invitation.
« Reply #34 on: June 08, 2011, 10:23:41 AM »
Quote from: "Stormrider51"
Quote from: "Two Steps"
What about water?  Large stock tank...swimming pool...my front yard after a rain :cry:
Al

Al,
I appreciate the idea but water is less "soft" than you might think.  It doesn't compress at all which would cause the ball to deform.

Thanks,
John
Maybe I watch too much TV. But on shows like NCIS and CSI they are always firing into a tank that they recover pristine bullets undeformed to compare rifleing marks. I also remember a show that was about the arsenal in Alabama where they refit and recondition weapons for the military that they fire into a tank and recover bullets.
Dunno.
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Offline Riley/MN

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Re: Testing round ball obturation theory. An invitation.
« Reply #35 on: June 08, 2011, 11:21:09 AM »
Quote from: "FlintSteel"
Maybe I watch too much TV. But on shows like NCIS and CSI they are always firing into a tank that they recover pristine bullets undeformed to compare rifleing marks. I also remember a show that was about the arsenal in Alabama where they refit and recondition weapons for the military that they fire into a tank and recover bullets.
Dunno.

I am guessing that those bullets are NOT pure lead....
~Riley
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Offline Stormrider51

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Re: Testing round ball obturation theory. An invitation.
« Reply #36 on: June 08, 2011, 11:45:26 AM »
That's correct.  "Lead" bullets used in modern firearms contain tin and antimony as hardening agents.  I wouldn't expect them to upset much at all under the low pressures developed by black powder.  I can score a mark with my thumbnail on the pure lead balls I cast.

John
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Offline Rasch Chronicles

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Re: Testing round ball obturation theory. An invitation.
« Reply #37 on: August 12, 2011, 01:18:34 AM »
Really interesting stuff.

I would guess if something blows up behind you, your behind starts to move before the front, causeing everything to pile up before the front gets a going! I wouldn't be surprised if a roundball becomes squished front to back.

Best Regards,
Albert A Rasch
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Offline Stormrider51

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Re: Testing round ball obturation theory. An invitation.
« Reply #38 on: August 12, 2011, 10:15:36 AM »
Hi Al,
Hope you are keeping your head down over there in "Stan".  I've continued to do a little experimentation from time to time on ball expansion or upset.  It's too hot here in Texas to do much outside so I hide out in my shop.  I cast some balls from wheel weights and included them in the tests as a comparison to pure lead.  I also tried different thicknesses of patch material.  Here's something that I thought was interesting.  When I pushed a really tight patch/ball (pure lead) combo completely through a barrel section and then measured the ball with a micrometer, I found an average .003" decrease in size front to rear and a visible flattening of the sprue area.  Did it come from the whack with my hand on the short starter, the pressure of me pushing the ball through the barrel, or both?  Regardless, the impression of the patch material where the rifling pressed it into the ball were very visible although I couldn't detect any increase in diameter.  If we are flattening the front of the ball on loading and it is humping up from the rear on firing then were aren't really firing a "round" ball downrange.  It would look more like a pumpkin.  The same test using a hard wheel weight ball didn't produce the same degree of flattening and I'd have to squint reall hard to read a difference on the mic.  Is that good or bad?  I don't know.  I need to take some pure lead balls and some wheel weight balls to the range and fire them for group at 100 yards because accuracy is what it's all about.

Storm
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Offline Rasch Chronicles

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Re: Testing round ball obturation theory. An invitation.
« Reply #39 on: August 12, 2011, 11:14:16 AM »
Strom,

I think that will be very interesting. I don't know much about shooting blackpowder per se, but it seems that the overwhelming consensus is that you need soft lead, thick patches (within reason), and tight fit, to get a ball to be accurate. Without soft (pure) lead, the ball won't deform into the rifleing and the patch won't be as effective a seal.

I had asked a similar question elsewhere because I wanted to build a 36cal Tennessee rifle as an all round game rifle. What I did not realize was that a 358 ball only weighs 68gr! I have 22 rimfire with bullets that heavy! Anyway before I came to that realization, I didn't undrstand why a 358 ball was considered marginal on deer. I assumed that it was something to do with the pure lead, so I asked about wheel weight lead, knowing it could be heat treated and hardened. So that's where my search started.

The long and the short of it is that I have now decided I will need to build two Tennessee rifles, one in 32, and the other in 50.

Best regards,
Albert “Afghanus” Rasch   
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Offline Stormrider51

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Re: Testing round ball obturation theory. An invitation.
« Reply #40 on: August 12, 2011, 03:34:46 PM »
Al... Do I need to say that I feel real sorry for ya needing two rifles?  Good, then I won't say it.   :lol sign  You can never have too many.  On the other hand, do you need two calibers in the same style of rifle or could you have two styles in about the same caliber or maybe a rifle and a smoothbore?  I'm just tossing this out as a thought.  

I may step on some toes here and if I do I'm sorry but opinions on minimum caliber necessary for deer sized game have changed a lot since 1959 when I first hunted with a longrifle.  My first rifle was a .40 and the deer I shot didn't seem to think that .390 was too small a ball.  I have to add that I was 8 years old, my father was God, and he taught me to pass on any shot where I wasn't absolutely sure of shot placement.  I didn't have a lot of choice since he was usually sitting right beside me in the deer stand.  Hunting distances in the Texas Hill Country tend to be fairly short anyway.  I passed on a lot more shots than I took.  I still do, come to think of it.  Anyway, back then most members of the now long defunct Powder Horn Club here in Austin were shooting originals or hand built reproductions based on original Pennsylvania rifles.  Plains style rifles like the Hawken hadn't come into vogue and the average caliber was forty-something.  Anybody who showed up with a .50 was toting a monster and could expect some good natured ribbing.  So what changed?  Nowadays I read that a .50 is very minimal when it comes to a serious hunting rifle.  Really?  Why?  I don't know.  Given that bit of info I'm surprised that the Colonists didn't starve to death when everything they shot ran away.  Did they limit themselves to squirrels, rabbits, and turkeys?  So what's with all the stories about killing bears?

I spent most of my adult life working as a paramedic.  One of the deadest of the DRT (dead right there) men I ever saw had been shot by his 8 year old nephew with a tiny .25 acp pistol that the kid mistook for a cigarette lighter.  The .25 acp is often referred to as a "mouse gun" and I'll admit it wouldn't be my first choice as a defensive pistol but this shot blew through the sternum and punctured the aorta, the main artery rising from the heart.  It was sort of like blowing out a tire.  The patient was dead despite our best efforts to save his life.  It wasn't the caliber, it was the placement.  I also worked an attempted suicide where the patient shot himself through a lobe of his right lung with a .44 Magnum.  He was still conscious and talking to us as we wheeled him into the ER and he survived the incident although minus a piece of his lung.  I doubt that anyone would call a .44 Mag underpowered but even so it didn't do the job the shooter desired in this case.  It's all about accuracy and shot placement.

I'm not saying that you shouldn't get a .32 and a .50 in the same style if that's what you want, just that I hunted everything from squirrels and rabbits to hogs and deer with a .45 caliber for a very long time.  Maybe a rifle and a smoothbore?  Then you could add birds to the list.  Just sayin'.

Storm
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