Unburned Powder As A Gas Check

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Bryan Austin posted this 16 August 2021

“ BELMONT, ONTARIO, May 6, 1903. “ F. W. MANN, MILFORD, Mass. " DEAR SIR : Yours of April 30 to hand, also box with bullets came yesterday at dinner time, a long time on the road. Upon opening the box and looking at the bullets I concluded I was ' dead stuck, ' for sure. However, before night light ( I think) dawned upon the whole matter. You are certainly doing some very original work, and on another sheet I give my opinion on the matter im mediately required . " Until the last portion of this unburnt powder left the bore it would act as a gas check and retain the gases and the pressure ; and (owing to the light weight of the powder) nearly all the pressure would be transmitted to base of bullet, as if the powder were a light but solid plug. Of course the unburned powder would expand outside of the bore but infinitely less rapidly than pure gas. The space between base of bullet and bore widens very rapidly owing to the forward motion of base ( due to upsetting) added to the velocity of the bullet en masse. But, until the upsetting is finished, this rapidly enlarging space is filled with unburnt powder pushed forward with the whole force of the burning powder behind . “ If all the powder were in a gaseous state when base of bullet left bore or if charge were ignited at forward end, the rapidly enlarging space due to the two causes above mentioned would allow the pressure to be reduced too soon to allow much work on base of bullet. You have certainly opened the gate into a large field . “ Regarding bullets 21 , 24, and 21 out of bore inch long, it is evident that the upsetting was done outside the barrel by a pressure against the base of the bullet, the said pressure being very much in excess of the cohesive power of the lead . “ The medium through which the pressure was transmitted to the base of the bullets was unburned powder.

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Squid Boy posted this 16 August 2021

I have used "powder as filler" (not any longer) and by the same process I suppose it could become a check. However, I can see the grains indented on the base of recovered bullets and have to assume that they do not become a solid mass but remain in a granular state. I would also have to assume that the gas can permeate this plug of powder quite easily. Shot to shot variation and only OK accuracy kept me from experimenting further. That and you could be working with an overload situation as you have powder available but are counting on it NOT burning. I figured there was more risk than reward and stopped. I shoot plain base only so I cannot comment further.  Thanks, Squid Boy

"Squid Pro Quo"

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Bud Hyett posted this 16 August 2021

Shooting 22.0 grains of 2400 in a .44 Magnum Super Blackhawk, we observed the powder kernel indents on the base of the bullet by chance. We next shot several other Super Blackhawks and a Marlin 1894 carbine, all with the same result. Even the 20 inch barrel of the Marlin carbine had the same pattern.

We theorized the powder was pushed against the base on ignition with enough force to indent, then consumed in the barrel without melting the base. The physical chemistry of time needed for generating enough heat to melt the base did not allow sufficient time to erase the indentations. 

The accuracy was there and each bullet had the indentations. We had no way to measure the quantitative value of the powder indentations. The load shot accurately and precise, the Marlin hampered by 1 in 38: twist of the early carbines. 

Farm boy from Illinois, living in the magical Pacific Northwest

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Bryan Austin posted this 17 August 2021

Upsetting the base of the bullets experiment

 

The first real experiment was made with 4- inch barrel laid in V -rest; placing a box of snow , with the thin cardboard which formed one end, in front of and 24 inches from muzzle, the first shot was made January 15, 1902. The bullet printed in center of target, point on , making a clean half- inch hole and was recovered from snow completely flattened by the muzzle blast , thus ac counting for large print through the cardboard . It is hardly possible for those not present during these tests to appreciate the condition of affairs which are here indicated and recorded for the first time. Experiments were made with these short barrels, extending over a year, with different lengths, different combinations, with various alloyed bullets, with nitro powders both coarse and fine grained . Eighty- nine 187 -grain bullets were secured in the same shape as they left the different muzzles. It was noisy sport and necessitated stuffing cotton into one's ears for protection. This medley of tests was carried on at the range with concentric action and V - rest and multiplied out of curiosity. Perhaps the accompanying cut ( Fig. 32) will be of interest as it represents the 187-grain unshot Zischang bullets and a number fired from short barrels. 

Figures 1 , 7 , and 14 are unshot bullets ; 2, 3, 4, 5 , and 6 are bullets fired from one short barrel into the muzzle of another, entering into and emerging from the .32-40 chamber of the second barrel. Figures 8, 9, 10 , 11 , 12 , and 13 were fired from a - inch .32-caliber barrel through a 3-inch .40-caliber which was firmly screwed to the former ; figures 15, 16 , 17 , and 18 were re markably upset with 21 grains sharpshooter powder, with no air space and .32–40 shell . All these bullets were loose- fitting or bore diameter. With figures 2 and 8 the charge was front ignited ; figures 6 and 13 were an alloy of 1 to 30, tin and lead ; figures 15, 16, and 18 were shot with 21 grains powder from a .32-40 shell , bullet entered half an inch into shell, leaving no air space, and extending .06 inch out of muzzle. The apparent tears seen in bullets were produced by a sharp steel prong, placed at varying distances from muzzle and also varying distances from line of low side of the rifle bore. 

This prong was accurately adjusted by a screw and by it was determined at what position from muzzle many of these bullets commenced to upset , and at what position they completed their upsetting. It was found that many of them commenced to swell slightly at .06 inch from muzzle, and all that were tested received their full upset during first inch of flight of their bases from muzzle. Figures 15 , 16, and 18 pretty well illustrate W. E. Mann's putty-plug theory. Figure 17 was fired from a .62-inch barrel , .32-40 shell full of Du Pont's .30 -caliber high -pressure powder, leaving no air space, body of bullet extending .06 inch from muzzle and no prong interposed to obstruct. It will be noticed that lead bullets, figures 2 to 6, and even the 1 to 30, after being driven through a 3.12 inch , .32-caliber bore, were expanded into the .32-40 chamber, completely filling it . These bullets continued to enlarge as they passed into the larger portion of the still enlarging chamber until their diameter reached .386 inch for lead , and .379 for the 1 to 30, showing that they filled the chamber for two -thirds its length where its diameter is .388 inch ; all this with a normal charge behind a loose fitting bullet . It will also be observed that front ignition, as in figures 2 and 8 , does not do away with upset , as has generally been supposed by some well-known rifle men. Shots represented by figures 8 to 13 inclusive, being bore diameter, not only upset into the .32-caliber rifling, but after traveling 3.12 inches they again upset and, with the lead bullets , completely filled a .40 - caliber to bottom and corners of the grooves. The putty -plug theory is here again confirmed, but does not encourage the theory that bullets must be larger than bore in order to take its grooves. Before snow-shooting and oblique -base experiments were made, or short barrel tests attempted, brother William claimed that a lead bullet in a rifle bore was like shooting a plug of putty from a popgun. A little later, while working on the range, this idea was again brought up when he asserted , still more emphatically, and seemed to show how soft bullets would stick in the bore, being pushed out sidewise, either side first as might happen , by powder blast behind , like pushing a plug of putty from a popgun, and it was decided to thoroughly test the matter. Measurements taken from bullet bases which were recovered during snow shooting experiments, seemed to bear out W. E. Mann's theory , and short barrel tests showed up his theory so thoroughly that they were multiplied until it was substantiated .

 

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Bryan Austin posted this 17 August 2021

I just thought the tests were interesting.
"The Bullets Flight From Powder To Target"  by FW Mann 

Published in 1909

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Squid Boy posted this 17 August 2021

In the particular case I mention there was a considerable amount of unburned powder left in the barrel and you could sweep it up from in front of the gun. The load in question had a predicted 60 or so percent burn ratio so I am sure that powder followed the bullet up the bore. Can I say that for certain? No. Mann had a lot of this figured out. Squid Boy.

"Squid Pro Quo"

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Bryan Austin posted this 17 August 2021

In the particular case I mention there was a considerable amount of unburned powder left in the barrel and you could sweep it up from in front of the gun. The load in question had a predicted 60 or so percent burn ratio so I am sure that powder followed the bullet up the bore. Can I say that for certain? No. Mann had a lot of this figured out. Squid Boy.

Oh yes, I agree. I use Reloder 7 and get a lot of "unburned" powder. My loads too are only showing about a 60% ratio. How consistent that though, I have no idea.

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Squid Boy posted this 17 August 2021

I think that is where the problem lies. The fuel is there but how much is burnt every time is the variable. I just didn't see consistent performance out of these loads and now try to keep them above 90% at least for that reason. Has anyone studied the effect of unburned powder on accuracy? That might be interesting. Thanks, Squid Boy 

"Squid Pro Quo"

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Bryan Austin posted this 17 August 2021

I think that is where the problem lies. The fuel is there but how much is burnt every time is the variable. I just didn't see consistent performance out of these loads and now try to keep them above 90% at least for that reason. Has anyone studied the effect of unburned powder on accuracy? That might be interesting. Thanks, Squid Boy 

 

Not that I can find. Also in the information in the book, Mann claims accuracy plummeted after 1,500 or so fps. Cant remember his exact words without going back and looking. In one part as well, he mentions that when using Sharpshooter, the bore had to be either very clean or untouched to shoot accurate loads. This too has been my experience withy Reloder 7. Either real clean or left alone. I have not cleaned the bore for several hundred loads.

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RicinYakima posted this 18 August 2021

We now call this "bore conditioning". 

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Ken Campbell Iowa posted this 18 August 2021

just mixing apples and oranges a bit ...

most mj benchrest competitors favor pretty high pressure loads ... frequently scary high ....   ...  i assume those are more accurate ... i assume because the powder burns more consistently at high pressures ...  

but for us here cast shooters trying to break 1 moa once in a while ... i doubt that scary high pressures hold much glory at that level ...  has anyone recovered cast bullets with skid marks on the side from unburnt powder ?? ...

... while reading Dr. Manns work, it reminds us that we need a good but simple/cheap way to recover cast bullets undistorted by catching them ...  maybe we could find why my deer rifles mostly shoot 2 to 3 moa with cast ...  

ken

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Bryan Austin posted this 18 August 2021

just mixing apples and oranges a bit ...

most mj benchrest competitors favor pretty high pressure loads ... frequently scary high ....   ...  i assume those are more accurate ... i assume because the powder burns more consistently at high pressures ...  

but for us here cast shooters trying to break 1 moa once in a while ... i doubt that scary high pressures hold much glory at that level ...  has anyone recovered cast bullets with skid marks on the side from unburnt powder ?? ...

... while reading Dr. Manns work, it reminds us that we need a good but simple/cheap way to recover cast bullets undistorted by catching them ...  maybe we could find why my deer rifles mostly shoot 2 to 3 moa with cast ...  

ken

Yeah, the "oil" and saw dust was a nice touch

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RicinYakima posted this 18 August 2021

It works well, and you can use a metal detector to look for the bullet in the box. We hashed this out a few years ago here. 

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Squid Boy posted this 18 August 2021

Back when I had an in-ground pool it caught a lot of bullets when the wife wasn't home. They were essentially undamaged but it took a lot more water than you would think to slow them down especially the 500+ grain stuff. I use packed wet snow to test jacketed bullets and it will destroy a poor one and bangs up cast bullets. Oiled sawdust worked for Mann but seems to be pretty messy and I would imagine that you would need a lot to stop a very heavy slug. Interesting stuff as always. Squid Boy

"Squid Pro Quo"

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