BP Pressures

[LynnC]

OK - I'm curious.  I've read that small calibers run high pressures and shotguns run low.  Where can I find info on BP & roundball load pressures???

I know someone can point me in the right direction !

Thanks...............................Lynn

[Dphariss]

Lyman's Blackpowder Handbook.

Dan

[northmn]

Lyman's Blackpowder Handbook.

Dan

That's a good one.  Possibly powder suppliers for the phoney stuff like 777.

Just a thought.  Smaller calibers are generally used with a higher ratio of powder to ball weight than big bores.  Shotguns even less and shot has less friction.  BP shot loads are said to work at about 5000 to 7000 psi as compared to about 9000 or greater for modern guns.  The 410 works at about 14,000 psi with shot as does the 3.5 12 mag.  Lyman has an interesting section of 54 3f and 2f pressure comparisons.

DP

[Dphariss]

As northmn pointed out the larger bores are more efficient than the smaller bores, better velocity or  bullet energy per grain of powder burned. So the small bores need more powder
The light balls have so little inertia that they need more powder to increase the inertia.
My 16 bore with a 29" barrel (30" to the rear of the standing breech) makes 1600-1650 fps with a 1 ounce ball and 150 grains of FFG Swiss.
This is about 34% of ball weight.
This would only be 32 grains in a rifle using a .395  ball at 93 grains. Many shooters use 50-60 to get best accuracy. Lyman shows 30 grains making 1343 and 35 1474 in a 43 " percussion barrel. we should be able to safely use 1400 for 32 grains

I believe it is related to *load inertia* the 1 ounce ball is harder to put in motion initially and the powder is used more efficiently. The lighter balls need the heavier loads to increase the inertia.
This is simplistic but I am pretty sure its part of it.
At 1650 the 437 gr ball makes 2642 Ft lbs.
At 1400 the 93 gr ball is making 405.
This is 12.65 ft lb per grain for the 40 cal.
The 16 bore flintlock makes 17.6 per grain in a shorter barrel.
Finally a use for muzzle energy in BP arms

Dan

[northmn]

While I haven't seen anything on this the larger bore ball does have to have more to push it.  In addition to the inertia required to get it moving there is the scaler effect.  A larger ball has more volume compared to surface area.  The surface area increases by the radius squared and the volume by the radius cubed.  There is less surface area to intially push against to get the larger ball moving.  Otherwise they would likely perform the same .  Smaller bores are generally loaded heavier for accuracy and performance.  On the flip side this also explains why a large bore retains velocity so much better.  Less friction acting against every grain of ball wieght.  They also penetrate deeper due to this and can withstand impact energy better.  The increased inertia also plays a part in this.  A 93 grain 40 is about half the weight of a 50 cal at about 180 grains but the diameter does not double.

DP

[LynnC]

Thanks Gents - Lyman BP Handbook it is.  I don't have a copy so I'll see if I can locate one.

The breech plug discussions over in gun building got me thinking just how much pressure is being generated about 6 or 8 inches in front of our faces..........................Lynn

[Daryl]

Lynn- with the vent or nipple, there is a very good pressure release valve - if numbers are scary, most modern rifle ctgs. today, are generating 63,000PSI just in front of your mellon, compared to 15,000 or less for BP guns.  A .38 SPL generates around 15,000PSI.

[LynnC]

63,000 PSI 

Thanks Daryl - That's why I refuse to work on anything modern!

Black Powder is much more in my comfort zone  ..........................Lynn

[northmn]

I guess Don Getz has had both health problems and computer problems or he could offer advice.  He used to talk about making a 13/16" 50 cal barrel.  Used a heck of a proof charge for testing.  My own opinion is that one needs to understand design and use of the guns.  Rear sights should not be dovetailed over the underpinning lug dovetail.  Especially if using a wedge.  Use a reasonable distance in front of the breech for any dovetailing.  Keep dovetails relatively shallow.  Make sure the breech plug is seated against the shoulder.  Don't try to make a "magnum" out of a caliber like the modern zip gun's promote.  If you need more power get a bigger bore.  Some of the slug concoctions I see on another web site used in inlines are ridiculous in that they would kick like a mule and offer little in performance increase.  When I chronograped my 50 I found that 80 grains of 3f performed so close to 90 grains that I cut back to 80.   More guns are damaged by misloading, such as an incomplete ball seat than anything else.  More than once, I have seen double charges and piggy back loads go off with no harm to the gun.  No one wants tooverload on purpose but the better made systems hold up.   

DP

[FL-Flintlock]

T.E. Thorpe lists the Deering cartridge pressure tests as follows:
Black Powder -
Maximum - 43 tons per square inch (86,000 psi)
Practical application normal operation - 17 tons per square inch (34,000 psi)
 
J. McAdams relates the Baxter-Wheaton explosive-driven penetrator test results as:
Maximum developed - 82,400 C.U.P.
Maximum operational bores under 1 inch - 39,000 C.U.P.
Maximum operational with opulent chamber* - 43,000 C.U.P.
*Not defined, believed to be bottleneck.

The Von Warnborg forced compression with secondary ignition test shows an average of 7515 Bar (109,000 psi) {Defined as: A secondary load compressed by normal operation of the primary load and ignition of the secondary load occurs after compression}
 

[Dphariss]

T.E. Thorpe lists the Deering pressure tests as follows:
Black Powder -
Maximum - 43 tons per square inch (86,000 psi)
Practical application normal operation - 17 tons per square inch (34,000 psi)
 
J. McAdams relates the Baxter-Wheaton explosive-driven penetrator test results as:
Maximum developed - 82,400 C.U.P.
Maximum operational bores under 1 inch - 39,000 C.U.P.
Maximum operational with opulent chamber* - 43,000 C.U.P.
*Not defined, believed to be bottleneck.

The Von Warnborg forced compression with secondary ignition test shows an average of 7515 Bar (109,000 psi) {Defined as: A secondary load compressed by normal operation of the primary load and ignition of the secondary load occurs after compression}
 

Peak pressures in "closed bomb" tests in the 19th century proved that 100Kpsi was possible but has little application to firearms which are not sealed.


30K + is not likely to occur with "musket or "rifle" burn rate powders. This is borne  out by Lymans pressure tests of the 45-120 with heavy bullets. They topped out at about 28-29K with Goex. Swiss will almost surely make more pressure but without actually testing is now known how much more.
This is a "Dutch Bill" topic and perhaps he will check in.

Dan

[FL-Flintlock]

Dan,

I corrected my initial reply, the Thorpe numbers are "cartridge" pressures.

[Daryl]

A agree it would be good to here from Bill - and Don too.  Starting to be concerned about that man.

 I know the .50 3 1/4 and .45 3 1/4 run pressures up close to 30,000O CUP - as tested by Accurate Arms and Lyman.  What many don't know, is the pipsqueak load of a .45/70, which is exceeded in every one of the inlines, is a 405gr. bullet and a mere 70gr. of 2F. That load generates over 22,000CUP according to AArms. considering Lymans top pressure in any rifle shooting a round ball - and at velocities up to 2,200+fps range produced only 15,000CUP which comes out very close to PSI in ML's.

[LynnC]

I recall Dons 13/16 - 50 cal tests.  300 grains and 1 or 2 balls and they didn't blow.  I've no idea what kind of pressure would be developed in that kind of major overload.

I'm strictly a moderate load patched round ball loader, flint & percussion, 36 cal up thru 12 gage.  No interest in modern zip guns with plastic wraped pyro pellet propelled mule kicker loads.  The 12 with round balls kicks plenty hard enough thank you!


Anyway, thanks for the input................................Lynn

[northmn]

Sometime back powder companies and manuals quit using the LUP and CUP as they found that they did not have a direct rating to PSI.  At one time they had a rule of thumb about LUP -2000 being PSI (something like that)  They found sometimes it was more sometimes less.  Now all manuals go to the PSI.  The cast bullets handbooks for the 45-70 list 18000 psi as about max for the trap door Springfield which they got testing BP loads. 

DP

[Mad Monk]

In dealing with the issue at hand one must realize that the small bores reguire a very fast and hot burning black powder to perform at their best.

Sam Fadala's Second Edition of the Lyman Blacpowder Handbook used Elephant and GOEX.  It would be nice to see something like that work comparing GOEX and Swiss.

The development of the very fast burning sporting type powders in the late 1700's into the early 1800's made the smaller caliber round ball guns practical weapons in the field.

If you use only a rifle burn rate powder you see the following pattern.

Shooting patched balls in the different calibers with a 32" barrel length.

The .36 caliber converts about 8.5 to 9.0% of the powder charge's potential energy into kinetic energy in the projectile.

The .45 caliber converts about 11.5 to 12.8% of the powder charge's potential energy into kinetic energy in the projectile.

The .50 caliber converts about 11.5 to 12.0% of the powder charge's potential energy in kinetis energy in the projectile.

The .54 caliber converts about 10.0 to 10.6% of the powder charge's potential energy into kinetic energy in the projectile.

In the case of the .32 and .36 calibers the rifle powder burn rate is too slow to take full advantage of the ability to accelerate the low mass of the round ball.
The rifle powder burn rate is best in the .45 and .50 caliber rifles.

When you get to the .54 caliber the rifle burn rate powder is a bit too fast for the greater mass being accelerated in the bore.


The gun is a simple single-stroke heat engine and you can look at its effeciency in conversion of the potential energy in the powder charge to kinetic energy in the projectile leaving the muzzle.

This data simply explains why in the 19th century there were three different burn rate black powders for use in small arms.  Those being, from fast to slow, sporting, rifle and musket.
 

[FL-Flintlock]

DP,

Yes, at one time there was some that claimed PSI was 2,000 higher than the C.U.P. number but more recent test data shows that it's not true.  At pressures below about 30,000 psi, the "2,000" differential had some merrit - but - in actuality, when they did numerous tests on the same load using the C.U.P. method, the C.U.P. method actually produced results varying by as much as 3,000 points on the C.U.P. scale.  L.U.P. proved more reliable than C.U.P. but still maintained a fairly wide error gap.  The same error gaps were noted using the C.U.P. method with pressures over about 50,000 psi - the higher or lower the pressure outside the mid-range of the C.U.P. method capabilities, the wider the error gaps became. 

Some examples at the 8x50R where the established C.U.P. was 54,000 and the actual PSI is 65,000.  The .308win 52,000cup / 60,000psi.  The .264win mag 54,000cup / 64,000psi.  The .35rem 35,000cup / 33,500psi.

Running on black powder, the .38-40 showed C.U.P. results from 8,000 to 14,000 for the same load that consistently produced 16,500psi over the duration of the testing by EBMR E-Trace.

[Daryl]

.45/70's. .458 Win Mags pretty much match up numbers , CUP and PSI.  I figured from this, that muzzleloading numbers must be pretty close as well, but perhaps only for .45 to .50 cals.

As to fast powders in the big bores, Forsyth was dead against using too-fast a powder in the bore guns as the larger mass of the ball needs a 'smoother' push, rather than the 'jolt' to get it moving.   

[northmn]

What the Mad Monk states follows what I have seen.  The big bores tend to be a little slower with the same powder lead ratio, especially at about 58 up.  Some of that may be due to powder types but a lot is as stated the scaler effect where a larger ball has less surface area for the gasses to push on as compared to volume. I noticed that Swiss powder comes in 1 1/2 F which is an intriguing size.  Cartridge shooters like it.   When one looks at the Lyman test data, 3f gave higher velocities than 2f but with higher pressures.  What this could mean if one erred, as in double charging is I think more important than whether one load or the other is suitable for targets or hunting.  In other words if 90 grains of 3f works safely in a 54 and makes a good hunting load, a what if is what happens with a 180 grain double charge.  (They can happen).

DP 

[Mad Monk]

Powder grain sizes.

The grain sizes we use today came into being in the 1830's and was part of a standardization in the industry.  But were not used as such until very late in the 1800's.

If you look at C&H grain sizes prior to 1890 you see a larger number of grain sizes covering the same overall range.

The basic concept in U.S. grain sizing.  The mean, or average, diameter of 2F is half the mean, or average, diameter of 1F.  The mean, or average, size of 3F is half the mean, or average, size of 2f.
This is a way of dealing with the amount of surface area for a given weight of powder.

But when dealing with the very fast, very hot burning sporting powders this grain sizing concept does not work with all of the different guns and loading configuarations.  So C&H used what might be called a 3/4 system rather than the halving.
The Swiss 1.5F harks back to that system.

[Mad Monk]

Forgot to mention.

The Swiss 1.5F almost exactly duplicates the old C&H #6 powder that was written about in old cartridge gun writings.

[Daryl]

 Appreciate your input, Bill.

[Dphariss]

.45/70's. .458 Win Mags pretty much match up numbers , CUP and PSI.  I figured from this, that muzzleloading numbers must be pretty close as well, but perhaps only for .45 to .50 cals.

As to fast powders in the big bores, Forsyth was dead against using too-fast a powder in the bore guns as the larger mass of the ball needs a 'smoother' push, rather than the 'jolt' to get it moving.   

Boy this velocity/bore/size/powder granulation/energy produced can cause headaches.
I ran Forsythe's  14 bore with "#15 ball" using 5 drams powder trajectories through a ballistics program years ago and came up with about 1600 fps.
This is what I get with a similar charge weight ,140 gr., of FFG Swiss in a rifle using a "#16"  ball in my flintlock so it would *seem* he was using pretty good powder since while his rifle was percussion his barrels were shorter by 2-4" IIRC.
He mentions "Hall's #5" but this is might be difficult to pin down but is probably much like FFG if they used C&Hs numbering system. It is likely that this 1850s powder would be superior or at least fully equal to Goex of the same granulation.

He also discusses using nipples that are apparently much like current design and states that some powder may come up in the nipple.
These two statements seem to contradict themselves....

He also mentions sportsmen using the "strongest mixtures".
Guess I will have to re-read his book again.

The classic pressure sign in percussion rifles is nipple erosion.  In playing with the picket rifle I find that 70 gr is FFG Swiss will not vent much gas at the nipple. 80 gr does vent but shoots better in testing to date. This seems to a be typical load levels for picket bullets of this caliber.  This with relatively light a 132 grain 40 caliber picket bullet.  However, I feel that this is the max usable load with the current breeching (steel Mowrey action) and I may end up building better rifle for this project now that it appears to be workable accuracy wise.
Chapman indicates (1840s) that pickets shoot better with lower grade, slower, powder.
But this is not borne out with Roberts' experience in the 1880s. The better powders, C&H and other high end sporting powders were the norm for accuracy, often C&H #6 or other FG high grade American powders. At least with elongated bullets.
This is a very complex subject, pressures and energy of the powder vs energy created by the muzzle velocity. It can vary widely from one rifle barrel to the next and this can cause "spikes" in the data.
With a rough bored ML  barrel, at least at the breech, BP velocity my actually increase over the same charge weight/ball size used in a smooth barrel. Rough boring the breech end of the barrels made shotguns shoot harder or so some English makers found in testing.

This increases "load inertia" and makes the powder burn better.
Load inertia and its increased pressure often improves accuracy especially with bullets where long range accuracy is important. It may well increase the projectile energy obtained from a given weight of powder all else being the same.
I think people that find water/spit lubes with the PRB may be increasing friction in the barrel and the increased pressure produces better accuracy in *that* barrel. There are other factors but this is one possibility

I would also point out that shooting at 50 to 100 yards is far different than shooting 200 with a PRB  or 200-1000 with a bullet. Loads that work very well at 100 are often useless or at least less than optimal at longer ranges.
 
With this is mind we need to understand that when "this load" produces "that velocity" in  this caliber rifle that there are factors at work besides just the ball size and powder charge. In fact internal finish may result in 3 different but *identical" PRB barrels by the same maker might produce markedly different results simply due to the finish on the lands.

Dan

[northmn]

One rule of thumb in Schuetzen shooting was that the most accurate cartridge combination was a heavy bullet coupled with a lighter charge, enter the 38-55 and 32-40 with a 200 grain bullet.  There may something to that passed over to roundball where the heavier ball can be more accurate with a lighter relative charge.  If you think about it, variations in powder charges thrown from a powder measure may be less significant.

DP

[Daryl]

Boy this velocity/bore/size/powder granulation/energy produced can cause headaches.
I ran Forsyth's 14 bore with "#15 ball" using 5 drams powder trajectories through a ballistics program years ago and came up with about 1600 fps.
This is what I get with a similar charge weight ,140 gr., of FFG Swiss in a rifle using a "#16"  ball in my flintlock so it would *seem* he was using pretty good powder since while his rifle was percussion his barrels were shorter by 2-4" IIRC.
He mentions "Hall's #5" but this is might be difficult to pin down but is probably much like FFG if they used C&Hs numbering system. It is likely that this 1850s powder would be superior or at least fully equal to Goex of the same granulation.

 
Dan

I agree - however in my own 30" 14 bore rifle, shooting a (probably) somewhat larger ball than Forsyth used, I tried just over 6 drams 2f GOEX to achieve 'his' trajectories and was successful in doing so.  With that 165gr. charge, I matched his diagrams of trajectories right to 125 yards.  It didn't mate with my program until I entered the exact sight placement.  (if I remember correctly)    Using 3F, I could have matched the velocities with lighter charges, but was unable to use a hardened ball with more than 3 1/2 drams without burning patches, hens I used MORE 2F to achieve the speed required but with less pressure - or perhaps it was merely easier on the patch due to slower pressure build.  It is a wondrous thing to achieve such a flat trajectory (long point blank range) from such a large bore rifle. Hitting the spot at any range becomes easy.

For some powder to come up the nipple, with a small hole at the bottom as Forsyth desired, the powder must have been fine indeed. Seems to me, the C&H powders we used in the 'early' days were considerably finer than the GOEX we use today.

That trajectory comes out at 25ys. +1.04";  50 yds + 1.66"; 75 yards + 1.26"; 100 yards 0.0"; 125 yards - 2.25"  I used .085" as the BC - which should be close for the .684" ball weighing 484gr. in pure lead @ 1,550fps.