breech pressure?

[JPK]

Is there a know and documented maximum presussor that black powder can obtain?

[Bob Roller]

The Swiss powders seem to have more "punch"per load than the old time DuPont,Goex and maybe een Curtis&Harvey.
Maybe Dan Pharris has some info on this.

Bob Roller

[hanshi]

I've read articles by experimenters who say pressures up to 100,000 psi can be produced with black powder.  An article appeared in The Gun Digest many years ago concerning bp pressures.  This information was included in this article,, as well.

[Daryl]

I've read the same thing, hanshi - perhaps a closed vessel test, but I don't know. Lyman seemed to hold their data to 15,000LUP, which does not cross-reference #'s to CUP or PSI.

Accurate Arms powder makers tested the ctg. guns normally used today- ie: .45/70's and longer Sharps rounds. They recorded a maximum pressure for a factory-type load in a 3 1/4" .45 case as delivering 30,000PSI - pezio measure. In the straight cases, this is very similar to the #'s derived by copper units of pressure & shows identical numbers in many of them.

Perhaps the question should be, what is the maximum for a cap-lock style ignition (whose make and what nipple size, design and oriface size?) with each breeching type, then flint, etc as well as all the barrel types. Unfortunately, there are so many variables in each type of ignition bore and outside dimension size as to make such a test prohibitively complicated and expensive while producing little useable data in our own guns, which are as variable as can be.  Just a thought.

We do know, the larger the bore, the lower the pressure for a 'given' load. We also know that with the largest bore sizes, excessive recoil stops further testing while pressures are still fairly low, in comparrison to the small bores wihc have very fast rises in pressure, ie: .40 to .50.

Lyman's book, while somewhat outdated to the powders we use today, shows us that when the velocities are similar, so are the pressures generated. From this, some extropolation can be made with reasonable accuracy - this, a 16 bore delivering it's round ball at 1,800fps, will be producing similar pressures to a .54 cal. rifle developing 1,800fps with it's round ball using the same powder.  In the larger bores, it will be seen that to produce 1,800fps and shoot the firearm from the shoulder is virtually impossible. My own 14 bore rifle needed 165gr. of 2f to achieve 1,550fps, while 225gr. achieved only 1,700fps - an accident in charging the gun showed a velocity of 1,770fps - but that one had 330gr.( accidently doubled the 165gr. charger). That one lifted me off my seat at the bench.

 Let me tell you that 165 is about all I can 'stand' when having fun shooting and that, with a PAST recoil shield. The muzzle's 'rise' with the normal max. load producing 1,550fps load is past 45 degrees.

So - what the actual pressures are, we won't know unless or until it is published or someone buys the strain gauge tools and does some experimentation for us.

[Dphariss]

Is there a know and documented maximum presussor that black powder can obtain?

In "closed bomb" tests back in the day it was found to make 100000 psi. Powder was ignited in a "bomb" that was too strong for it to burst.
Large capacity BP cartridges can make as much as 30000 with a heavy bullet, this from Lymans pressure data.
In firearms this is about the max.
In MLs shooting a Patched RB 15000-18000 is about max. But would have to refresh my memory an its too late tonight to look it up.

Dan

[hanshi]

I tend to agree with your numbers, Dphariss.  In my reading these same pressures are recorded over and over.  I'd guess, that while 15000-18000 won't blow up a reasonable well made barrel, other factors - such as recoil, hammer blow back, spitting and erosion - effectively limit pressures pretty much to these levels.

[bob in the woods]

Also, consider that a flintlock , or matchlock etc, is a vented system. I assume that this would tend to even lower breach pressure.

[Daryl]

Agree, Bob, however that is material only when considering the same mount of powder being used across differing ignition types.  The most vented or most loosly loaded which produces a similar sort of venting, will produce the lowest speed & lowest presssure all else being equal - barrel length, powder make, grains weight, ball/bullet, etc.  

Seems that with round balls in normal calibrers at a 'given' speed, 'X' psi is being developed regardless if of the same ignition type.  Lyman's book is quite worthwile in this regards - as showing similar pressure for similar speed, no matter the calibre. Because they used a method of measure not commonly used, matters not - that the numbers are so close is the important aspect.

Some cap locks vent easily, while others must have much greater presssures generated before lifting the hammer off the cap. That most cap locks shatter or split the cap is evidence those locks are also venting at the nipple.  The mechanics of the nipple's innards and the locks main spring strength being quite important in this regard.

Even with all the discrepacies or possibilities, Lyman's data is quite uniform.

[bob in the woods]

Thanks for the information , Daryl.  I am quite happy with my 10 bore hunting load of 140 gr FFg . I don't think I would be in a hurry to  regularly shoot 165 gr !! [  although, I did double charge by old Brown Bess once  ie
100 gr x 2.  That was at the Provincial muzzleloading matches in Chatham ,Ont.  The shot went high ! ]

[Daryl]

Taylor attended the Nationals at Chatham - years ago, and won 27 first place prizes inculding the all round aggregate which was a commercial cap gun- sold it upon returning to BC. He used his .62 Hawken - I think he was using around 140gr. 2f at the time with a 615"pure lead ball. He had plaques mounted all around the Rec. room, on the walls.

[Dr. Tim-Boone]

He da Man!!!  just 27 shots at 140 grains and I would be done.......

[Daryl]

Need I say that was SOME numbers of years ago.

[doulos]

Being one who has shot quite a few shots from a .58 cal Hawken I usually flinch just hearing the terms Hawken ,and .62 caliber in the same sentence.

[Daryl]

I didn't make note of it but his brand new S.Hawken is also a .62. He's even found a decent 200yard load at around 130gr. I think that's a bit light, however that curved butt 'do tell' on one's arm after a few shots.  An extra pad is necessary for bench work and a lot of concentration for non-pad shooting.
I'll stick with the 2" + English plate, thanks.