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Very Hot Topic (More than 25 Replies) Dr Mannís shooting tests c.1900 still relevant? 4 (Read 1651 times)
RSW
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Dr Mannís shooting tests c.1900 still relevant? 4
Jun 12th, 2019 at 12:02am
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Questions and notes:
While oblique bullet bases as a cause of rifle inaccuracy was not Mannís most significant finding, those experiments may be particularly relevant to todayís BPCR shooters. The image below was added to show square and oblique bullet bases.
Dr Mann stated in no uncertain terms that he found ďboreĒ diameter soft lead bullets would upset to full groove diameter on firing and overall were more accurate than groove diameter or larger than groove diameter bullets.
HOWEVER, IMO: when a bore diameter soft lead bullet upsets on firing to full groove diameter, how could the base remain square to the bullet body, other than by chance? What effect do randomly oblique bullet bases have on accuracy?
Could bullet bases upset oblique to the body on firing be a significant factor in it being so difficult to get PBCRs to shoot consistently better than approximately 1.5 MOA?
Has anyone done tests in recent years to capture undamaged lead bullets that had been fired with black powder and measure to find if the bases were still square with the bullet body?

The Bullets Flight from Powder to Target by Dr. F.W. Mann is available for download in PDF format. An internet search will locate a copy of the file.
« Last Edit: Jun 12th, 2019 at 12:08am by RSW »  

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Just Jim
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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #1 - Jun 12th, 2019 at 1:50am
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Hmm, VERY interesting! Thanks for opening the discussion, and I look forward to reading what others may have to add.
  
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frnkeore
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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #2 - Jun 12th, 2019 at 2:48am
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Two things, come to mind, regard the oblique base. First is imbalance and the second is a variance, in the drag pattern, both would induce yaw.

Frank
  

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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #3 - Jun 12th, 2019 at 6:51am
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The fact that we now use Poly or Fiber wads in our target loads not only protect the base from the powder impacting the base but could they also stop the angular deformation that Mann found?  Wads normally increased the accuracy of the bullet in my experience.  Never recovered bullets just saw results on target at 600 yards.
  
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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #4 - Jun 12th, 2019 at 9:16am
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I do know that my bore diameter paper patched bullets are pretty much as accurate as groove diameter bullets when using black powder.   The groove diameter bullets might have a slight edge.

RSW have you seen the version of Mann's book with Pope's handwritten notes?  If I remember correctly he took some exception to Mann's statement about very soft lead bore diameter bullets being most accurate.  I can try scanning the comments.  His handwriting is super hard to read.

Chris.
  
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Bill Lawrence
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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #5 - Jun 12th, 2019 at 9:24am
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This is indeed a very interesting topic.  Plus being a bear of smallish brain, it gave rise to this thought.  The point here seems to be that one accuracy help is not disturbing the uniformity of the base and its squareness with the vertical axis of the bullet.  Therefore, were it possible to cast such, would a bullet with a perfectly domed base not only be as accurate as a square base but also less likely to acquire an oblique base?

Also, is it always or at least almost always 1-in 5?  If so, why?

Bill Lawrence
  
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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #6 - Jun 12th, 2019 at 9:33am
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RSW, here is a link to a scan of that page.  Pope should have been a doctor or pharmacist based on his handwriting.  I cannot deciper it, but maybe someone here can.

Beware, the image is huge.  I wanted to preserve all of the detail.

Chris.

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marlinguy
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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #7 - Jun 12th, 2019 at 10:09am
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The biggest thing concerning me with a oblique base is how it's affected as it leaves the muzzle. It would be no different than a flat base on a oblique crown, and will kick the bullet's base to one side as it exits. This instability induced upon exiting the bore would have huge affects on accuracy, and destabilize the bullet instantly as it exits the barrel.
  

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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #8 - Jun 12th, 2019 at 10:12am
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Well...it ought to be possible to cast a nose pour domed base. (?)

Acknowledging that bp has about twice the rate of pressure rise as smokeless does the canting of the base disappear or minimize with smokeless?

In like manner does a gas check affect base canting.

Just asking as I have no answers. :Wink
  
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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #9 - Jun 12th, 2019 at 10:30am
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No doubt the bullets shown would have trouble shooting a clover leaf at any distance, but the big question is how they got the shape they are showing.

My first thought is poor casting. The right hand bullet with the most deformation, shows no sign of compression in the bottom lube groove. Maybe with careful measurement it would. That would seem to indicate a soft spot or void in the base.

Mann also had photos of bullets he had cast where the tips were cut off and wire inserted into the voids found. Those examples would correspond to the angles of the bases shown. I don't remember a mention of doing the same at the base.

A proper test would be near impossible. Choose a perfect bullet and measure. Load it, pull it and remeasure. Load it again and shoot it. Only then would you know when the deformity happened and under the which pressure.

I suspect that this is one of the reasons that Pope was a proponent of muzzle loading. The direction of engraving the bullets would have much less effect on flight consistency than the deformation to the base of the bullets shown, if it happened during loading. Compressing an uneven powder column with a bullet or a poor start breech seating seems to make more sense than uneven gas pressure in a cylinder.

Link to page 262 showing wires in the bullets with voids and part of this discussion

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llet+bases&source=bl&ots=kwjD6Z6Tky&sig=ACfU3U3xzZeK09VBUzetTOMw41Sfj8H2ww&hl=en
&sa=X&ved=2ahUKEwi30PGtleTiAhXkMXwKHZf8At0Q6AEwA3oECAkQAQ#v=onepage&q=squaring%2
0bullet%20bases&f=false

« Last Edit: Jun 12th, 2019 at 10:41am by Dellet »  
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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #10 - Jun 12th, 2019 at 10:45am
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cheap test on the round base would be to simply shoot a bullet backward? Couldn't use your tapered mold probably, but a cylindrical would answer.
  

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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #11 - Jun 12th, 2019 at 10:46am
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Dellet
That last image of the three bullets with square and oblique bases is purely to show the angle of the oblique bases as discussed by Mann. Those are Photo Shopped images that I distorted for illustrative purposes and not actual recovered bullets. Perhaps I should have been more specific about that point.
Bill
The 1-in-5 according to Mann's findings was an average. 1-in-5 was random as was the amount bullet-to-bullet base deformation.
cheatin_charlie
Some of Mann's tests were fired with no wad, others with Leopold's Oleo wads. Bullet base deformation randomly occurred with or without wads.
gunlaker
Thank you for that image with Pope's notes. I downloaded and will read later.
« Last Edit: Jun 12th, 2019 at 11:09am by RSW »  

Randy W
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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #12 - Jun 12th, 2019 at 10:50am
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desert-dude
Mann did conduct tests with hemispherical bullet bases. Accuracy was poor.
  

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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #13 - Jun 12th, 2019 at 11:15am
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If the deformity is random, then so is the cause.

Assuming the rest of the loading process was tightly controlled and looking at the quality of the bullets shown in the link provided, I still lean in that direction.

Something else to consider was in a new book I was just reading. It seems there was a corresponding jump in competition scores with the adoption of semi-smokeless powders.
Could base deformation, or lack of, be part of that reason?
  
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Re: Dr Mannís shooting tests c.1900 still relevant? 4
Reply #14 - Jun 12th, 2019 at 11:41am
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How does one measure the ?obliqueness?, the angle between the ?flat? base and the invisible long axis of the bullet?
  
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