Has anyone got access to real BP pressure curves ?

[KenH]

I don't wish to put any pressure on Larry for the tests, this post is just to keep the thread in everybody's mind and keep it from getting lost. This is a most interesting thread.

[mehavey]

Larry's probably waiting for a day that doesn't resemble an icebox.

[Larry Gibson]

Mostly, Larry needs to cast some bullets........

[charlie b]

And Lake Havasu City, AZ is not nearly an icebox He might have to wear something like long pants and shirts rather than shorts and sandals

[KenH]

Mostly, Larry needs to cast some bullets........

Larry, you just take your time and work at your own convenience. I'd be happy to cast up some bullets for you if wish. I've got the Lee 405 HB bullet mold you mention. I've got some pure lead and plenty of pewter (tin) to mix a 20-1 (or 16-1) mix. For a 16-1 mix, that would be around 8.6 oz of pewter to 8 lb of lead? Of course the % of tin in the pewter is the determining factor. I've read pewter can be from around 92% to 95% tin depending on the manuf.

Larry, I'll be happy to help. No point in you doing all the work, just tell me how many bullets you need shipped to you.

[Larry Gibson]

KenH

Appreciate the offer. PM sent.

[Larry Gibson]

Cast a couple hundred up this afternoon. Lee 405 HBs.

Attachment 275517

[dtknowles]

Yes, the above diagram is relatively correct as is your assumption; " This is where I would submit that effective bullet upset/obturation occurs -- that sharp high-pressure punch well above Brinell-derived deformation pressure of the alloy (BN*1,420psi) -- and gives significant advantage to smokeless for cast bullet shooters."

I can do a test specific to this question and would prefer to use the 45-70 cartridge?

Look what I found, it is for 45-70 but is a bit cryptic.

Attachment 275521

No units on pressure and no bullet weight but interesting anyway.

Tim

[KenH]

The pressure graphs look hand drawn, but the tables show pressures. Much like many have felt, BP actually gives higher peak pressures than a mid range smokeless powder like 4759. Looks like 4759 pressures are in the 15,500 to 16,500 psi range while FFg is 19,300 to 21,500 psi. I'm "assuming" those are for the same weight bullet and velocity, but that chart doesn't tell for sure. It will be really interesting to see what Larry's results are with his pressure equipment.

[dtknowles]

The pressure graphs look hand drawn, but the tables show pressures. Much like many have felt, BP actually gives higher peak pressures than a mid range smokeless powder like 4759. Looks like 4759 pressures are in the 15,500 to 16,500 psi range while FFg is 19,300 to 21,500 psi. I'm "assuming" those are for the same weight bullet and velocity, but that chart doesn't tell for sure. It will be really interesting to see what Larry's results are with his pressure equipment.

The charts have velocities and I am guessing you are suggesting that the reported pressures should be multiplied by 100. Few people explain their testing and data as well as Larry.

Tim

[crackers]

I thought this was settled back when the first guy blew up a BP barrel with nitro. 'Progressive burning' isn't a political statement.

[JSnover]

I thought this was settled back when the first guy blew up a BP barrel with nitro.

Come on, you know nothing's ever settled
I'd like to see the actual curves to compare the spikes and the timing and how quickly the pressure drops from the peak. Of course that'll only start more arguments but at least we'll have some good data.

[dtknowles]

I thought this was settled back when the first guy blew up a BP barrel with nitro. 'Progressive burning' isn't a political statement.

You can blow up a nitro barrel with smokeless powder. Back more than a century ago the factories loaded what were called Nitro for Black cartridges. What is settled is you can load nitro in black powder cartridge firearms but you have to know what you are doing. You should not be reloading anything if you don't know what you are doing.

Actually they don't call it Nitro for Black anymore but a bunch of factory ammo loaded with smokeless powder is loaded to low pressures so that it is safe to shoot in guns made before the switch to smokeless.

You might be talking about muzzleloaders but that is not what this thread is about.

Tim

[dtknowles]

Look what I found, it is for 45-70 but is a bit cryptic.

Attachment 275521

No units on pressure and no bullet weight but interesting anyway.

Tim

I made a new graph with my best interpretations of that picture in my original post.

Attachment 275562

Tim

[mehavey]

new graph with my best interpretations

Just so, Tim.
That spike is the BIGgest reason we tell folks to avoid TrailBoss is old/non-modern steel firearms.

[dtknowles]

Well a couple considerations. I only have GOEX FFg, FFFg and Cartridge. No one in this AO has any BP for sale that I know of. Obtaining other than those BPs may be a problem given the normal BP restrictions let alone the COVD situation.

For smokeless with the Lee 405 HB bullet cast of 16-1 or 20-1 alloy I suggest Unique, 2400, RL7, 3031 and 4895. I would hold velocity at 1300 fps +/-.

Name your poison....?

For Black Powder I would suggest Goex FFFG (I really don't think it matter much which PB you use) like is in the plot I made. Unique could be a stand in for Trail Boss, since it is the closest for burn rate. For the slower powder I don't know which to pick it is sort of a toss up but if I would have to pick it would be RL-7. I know that 2400 is a good choice but it is not enough different from Unique to prove/disprove the point.

Tim

[dtknowles]

Just so, Tim.
That spike is the BIGgest reason we tell folks to avoid TrailBoss is old/non-modern steel firearms.

Agreed but your point:

"yelling matches that go on about what's best for bullet obturation to seal the barrel for cast loads.

I maintain that a fast smokeless powder is far more effective in "upsetting" the cast lead projectile in that regard, when compared to BP."

Would point to Trail Boss being very good for bullet upsetting and bullet obturation, just not good if you have a weak gun.

Tim

[mehavey]

Would point to Trail Boss being very good for bullet upsetting and bullet obturation,

Yes. Correct.
In moderns guns.
(Which is where this whole thread started.)

[mehavey]

Unique could be a stand in for Trail Boss, since it is the closest for burn rate.

"Burn Rate" charts have gotten more people in more trouble than loose women.

"Burn Rate" is the speed of unpressurized powder.
It is only ONE factor in a powder's ballistic response:

- Burn Rate/sec
- Energy content (Heat/Kg)
- Ratio of specific heats (specific heat at constant pressure vs and the specific heat at constant volume)
- Progressive (or de-gressive) burning rate (with increasing pressure)
- Progressive burning limit (at which point it quits increasing pressure)
- ...and last but not least: a "Factor b" to balance the thermodynamics

As you can see, don't ever use simple Burn Rate to estimate loading results.

[Goofy]

http://www.texas-mac.com/Black_Powde...bturation.html