Load Pressure Long barrel, Short Barrel

[zimmerstutzen]

The figures were indeed from the Lyman book.

The max pressures measured were generally higher for the longer barrels. So if a 26 inch barrel gave x maximum pressure and the 40 inch barrel gave x+ maximum pressure, there is obviously pressure still building in that extra 14 inches of bore near the muzzle. If the pressure curve was on the down side after 15 inches, the maximum pressures for all lengths would be the same. it isn't.

The figures from the Lyman book show the pressure is still building between 28 inches and 40 inches.

The only reason for such increasing maximum pressure that I can think of, is that powder is still burning and increasing pressure in those last few inches of bore. The pressure curve must still be climbing at 26 and 28 inches, definitely not reducing after 15 inches as some theorize.

 

[Dphar]

Now ironically for a 50 cal in the Lyman tests, the 60 grains of fffg produced a slightly different curve

26 inch 1461 7800 LUP
28 inch 1460 8100 LUP
32 inch 1554 7900 LUP
43 inch 1611 7800 LUP

It still shows an increase in pressure between 26 to 28 inch barrels. But still disproving the idea that powder pressure curves reduce rapidly after 12 to 15 inches. the max pressure continues to increase even after the ball has traveled 26 inches.

if we increase the powder to 80 grains in a 50 cal.

26 inch 1690 11,000 LUP
28 inch 1692 11,400 LUP
32 inch 1777 11,400 LUP
43 inch 1854 11,700 LUP

still shows increasing pressure after 26 inches of bore.

These pressure figures were obtained with lead crushers and will ONLY show the PEAK pressure. Period.
They are incapable of any other information.

Long barrels in this context ALWAYS give higher velocity. About the only thing that produces slower velocity in longer barrels is the 22RF or similar cartridges loaded with small charges of fast smokeless. Memory tells me that the HV 22LR peaks at about 18-20" and longer barrels produce slightly lower velocities.
The pressure variations in Lyman could be caused by almost anything. Larger variations than this could occur between different cans of powder from the same lot or even from powder in the same can.

Dan

 

[Zonie]

Perhaps the first edition of the "Lyman Black Powder Handbook & Loading Manual" was printed using the lead crusher method of determining pressure however, the second edition was not.

On page 145 the book says:

"...All pressure data collected was with the use of piezo electronic equipment and is measured in actual pounds per square inch (PSI). Standard black powder barrels were modified to accept a pressure transducer and were connected to a peak pressure meter. If no pressure data is listed, an actual firearm was used for testing and only velocity was recorded..."

I was ignoring the "LUP" on the data given above but a lead crusher was differently not used for the data in the second edition.

As for the comment about longer barrels data showing the pressure was higher, the assumption that the longer barrel caused the higher pressure may not be correct.

Some of the longer barrels have a different rate of twist that was in the shorter barrels.
The bores of the various barrels may be slightly different in size and there is any number of things that can affect pressures in that first 8-18" of barrel length ahead of the breech.

As much as I like the Lyman book, there are also some unusual bits of data which are totally baffling to me.

For instance, on page 190, the .50 caliber 28", 1:48 twist barrel data says 40 grains of GOEX 2Fg produced 5,000 PSI while 40 grains of GOEX 3Fg in the same barrel produced only 3,800 PSI. Obviously a mis-print, but which number is wrong?
Maybe they are both right? Strange indeed.

The max powder load in this barrel listed is 120 grains under the roundball.
This load using GOEX 2Fg produced 7,800 PSI and the GOEX 3Fg powder produced 10,800 PSI.

The same powder loads in the .50 caliber, 24", 1:48 twist barrel on page 178 said 40 grains of GOEX 2Fg produced 2,600 PSI and 40 grains of GOEX 3Fg powder produced 3,400 PSI.
Looks lower than the long barrel, right?

This same barrel using the max 120 grain powder load shows the GOEX 2Fg powder producing 9,900 PSI and the GOEX 3Fg produced 11,800 PSI. Looks higher than the long barrel.

I think the moral of the story is the data is interesting and the book is a good reference but we should be cautious in drawing any major conclusions from it.

 

[zimmerstutzen]

But the one inescapable fact from the earlier book is that PEAK pressures are generally higher in longer barrels.

I agree that very light charges fizzle out and slow down before muzzle exit. But with moderate charges, the pressure appears to keep climbing with barrel length.

 

[Swtodd]

Yes, but as Zonie said, too many variables to make it absoulute.

steve

 

[zimmerstutzen]

Your right Toots. When the published statistics show that someone's position is mistaken, their fall back next step is to attack "the variables"

Check the book for yourself. Lyman's Black Powder Handbook 1st ed. Compare the figures for charges and barrel lengths. The same trend is found over and over, dozens of times. For lots of different charges and calibers.

The OP asked if there was any proof of what he thought was correct. I simply pointed out that despite the misleading assertions of mistaken "fact" that several posted, there are indeed published figures that prove there is a general correlation between longer barrels and higher pressures.

Folks mention tests with 45-70's and 22Rf's and modern smokeless or black powder cartridge pistols. All of which have absolutely nothing to do with round ball pressures.

 

[matt denison]

Can't argue with a guy with a Lyman book in his hand. :grin:

The information is provacative. My intuition tells me we (or I ) are missing something.

To be continued

 

[plastikosmd]

I doubt any laws were violated, all variables are probably not accounted for. I think a major issue (esp with blackpowder) is the lack of complete ignition, leading to some error in volume of gas generated calculations. I would guess the volume of gas generated by the charge is still greater than the volume of the internal of the barrel. Powder that remains in the reaction continues to burn in the longer barrel adding to the pressure/volume. Once the projectile is out of the shorter barrel, the unburnt powder is of no use. I do not know the efficiency of the system but would imagine more time to burn = more burn = more energy produced. I would also guess that the barrels are still too short to see the eventual drop off that would happen. Once the volume of the system equals the volume produced by the reaction you would start to see the drop. It is also not too surprising the larger caliber with a greater volume has a lower pressure reading per unit area. Remember the old psi drawing of a closed system with one piston being 2x the size of the smaller and the pressure and volume changes. I would expect the drop would happen sooner in the larger caliber as you continued to increase length as the volume changes by the cube. This is all dandy, then you start talking about friction etc and the system becomes even a bit more chaotic. Of course none of this matters if you dont hit what you are aiming at!

 

[Swtodd]

Maybe you can look at your 50cal, 60gr data and see what i refer to.

steve
Oops, wanted that to respond to Zimmerstutzen. Sorry.

 

[Dphar]

Perhaps the first edition of the "Lyman Black Powder Handbook & Loading Manual" was printed using the lead crusher method of determining pressure however, the second edition was not.

On page 145 the book says:

"...All pressure data collected was with the use of piezo electronic equipment and is measured in actual pounds per square inch (PSI). Standard black powder barrels were modified to accept a pressure transducer and were connected to a peak pressure meter. If no pressure data is listed, an actual firearm was used for testing and only velocity was recorded..."

I was ignoring the "LUP" on the data given above but a lead crusher was differently not used for the data in the second edition.

As for the comment about longer barrels data showing the pressure was higher, the assumption that the longer barrel caused the higher pressure may not be correct.

Some of the longer barrels have a different rate of twist that was in the shorter barrels.
The bores of the various barrels may be slightly different in size and there is any number of things that can affect pressures in that first 8-18" of barrel length ahead of the breech.

As much as I like the Lyman book, there are also some unusual bits of data which are totally baffling to me.

For instance, on page 190, the .50 caliber 28", 1:48 twist barrel data says 40 grains of GOEX 2Fg produced 5,000 PSI while 40 grains of GOEX 3Fg in the same barrel produced only 3,800 PSI. Obviously a mis-print, but which number is wrong?
Maybe they are both right? Strange indeed.

The max powder load in this barrel listed is 120 grains under the roundball.
This load using GOEX 2Fg produced 7,800 PSI and the GOEX 3Fg powder produced 10,800 PSI.

The same powder loads in the .50 caliber, 24", 1:48 twist barrel on page 178 said 40 grains of GOEX 2Fg produced 2,600 PSI and 40 grains of GOEX 3Fg powder produced 3,400 PSI.
Looks lower than the long barrel, right?

This same barrel using the max 120 grain powder load shows the GOEX 2Fg powder producing 9,900 PSI and the GOEX 3Fg produced 11,800 PSI. Looks higher than the long barrel.

I think the moral of the story is the data is interesting and the book is a good reference but we should be cautious in drawing any major conclusions from it.

Hi Zoni

With the proper equipment transducers will give a pressure curve. But I don't think Lyman bothered.
Transducers are also more consistent I think.
I have never purchases newer issue of Lyman's book. The velocity data is of some use. The pressure data is really not important and the trajectory tables are to set up to be useful for a long point blank range from hunting. In glancing at the newer eddtions over the years I found no compelling reason to buy one.

Anyway....
I will try again to shed some light on the "mystery" we seem to have here.

There were SIGNIFICANT variations in powder from can to can (or even in the same can) in the time frame we are discussing (I was using quite a but of powder at the time in competition.) As a result there is no way to draw conclusions. Its impossible. There can be significant pressure and velocity changes within the same can of powderand certainly from lot to lot.
So... Did they pack one can/case/lot of powder with just a little more moisture content? Did they put just a little too much graphite in the drum when "polishing" the powder? Was the steam used to stick the graphite perhaps a little too much? Did they make one lot of powder during a period of little rain fall? This increases the concentration of SULFUR OXIDIZING BACTERIA in the water. Then when making powder with the water the bacteria EAT the sulfur starting when the water is added and the powder tends to turn to dust IN THE CAN. Were the can lids loose? Many were and as long as the oxygen level is high enough the bacteria would be at work. If sealed the bacteria would eventually go dormant until the can was opened. So back before Swiss the first thing done when new powder arrived was to tighten all the lids.... Yeah.
The "bugs" and having a slightly too high moisture content was why some cans of powder had rust from the can mixed with the powder. I have heard reports of cans developing holed from the inside out due to rust.

Back before the move to Minden throwing away 1/4 of a can of Goex powder was "normal" since there was that much dust in the cans. This will not be apparent in loading a ML but in loading BPCR ammo with a drop tube its very apparent since the powder falls faster than the dust. So when dust appears in the cartridge case the powder is thrown away and a new can opened. The dust, for whatever reason settled in the bottom 1/3-1/4 of the container. So pouring it into a powder dispenser like a Belding and Mull or RCBS etc. allowed the dust free powder out first. It was not really apparent until drop tubed.

I seriously doubt that Lyman knew of or even noticed the dust and if they did it was afterall "normal". ALL the powder did this to some extent.
Even the grains that are not destroyed are more porous and this changes the burn rate. They were weak and would crumble then the load was rammed on a ML.
This was a problem from the time Dupont shut down the boilers and stopped using distilled water (the standard back in the day) in the process. It had serious effects on the powders performance in firearms, as fuzes and and booster charges in propellants. In fuzes and boosters, I have read, there were serious "events". I do know that during my time in service, for example, we had all baseball grenades picked up since they had some with "instant" fuses, this is not desirable in hand grenades. Years later I learned there was a lawsuit against the powder maker. Yes, grenade fuses are made with BP.
The move to Minden eliminated the bacteria problem, no sulfur oxidizing bacteria in LA it would seem and a change in suppliers eliminated the problem with impure saltpeter, this also causes significant performance variations since its impossible to maintain the proper moisture level in the powder. So from the chemical standpoint Minden powder is superior and overall is superior to powder made at the Moosic plant in PA.
Having some sodium in the saltpeter was why some lots of powder used to suck up humidity and get relatively "wet". Extra moisture, even 1%, will significantly effect performance.

So given the possible powder variations variable results are going to be the norm. If Lyman had BLENDED 200 pounds of powder and sifted all the fines out their results may have been more consistent.
Back in the days before Swiss a friend who has spent decades now studying BP, performance, manufacture, process and ingredients used to tell me what lots to buy for minimum bacteria content.
Prior to retirement he used to have access to a lab that let him, for example, count the bacteria in a powder sample.
I would point to this website for some information that might help some of the posters here understand BP a little better.
http://www.laflinandrand.com/page3.htm


I have many times this much info that "Monk" has sent me over the past 25-30 years just on powder.

Dan

 

[Dphar]

Now if I would just learn to proof read :wink:

Dan

 

[nkbj]

The time at pressure plays an observable factor in Lymans LUP data. Shorter barrels with the same charge of powder and lead make for lower total pressure readings. Those are not peak pressure readings as in pounds per square inch but rather a measure of the work imparted before the projectile clears the barrel. Works the same way as the comparison earlier made in the earlier post.

 

[Swtodd]

PM sent.

steve