Lead bullet pressures are greater than jacket bullet pressures of the same weight

[RobS]

Figured the thread could have some more data. I'm not saying one way or the other as it's been tested with labs to show both an increase in pressure/velocities with cast bullets, however not all cast bullets are the same. I know this data is formed with the use of Cast Performance Cast Bullets and their BHN as stated on their site is 18-21 BHN. Other data could have been used with softer bullets, swaged bullets, who knows and there in lies more variables to load data that is published by companies that use pressure testing equipment.

[Bullshop]

What is SFT, and what is CPB ?

[RobS]

What is SFT, and what is CPB ?

SFT = Swift Bullet company jacketed HP and CPB = Cast Performance Bullets a bullet company

found the PDF online finally.........page 17
https://www.hodgdon.com/PDF/Hodgdon%...c%20Manual.pdf

https://www.midsouthshooterssupply.c...sku=0019245325

[Newtire]

Better check your facts.
Typically the babbitt material covering main and rod bearings contains less than ½% lead (like o.3 or o.4%).
They are a tin based alloy and contain more copper and/or antimony than lead. They work because of a "pressurized" lubricating system that "floats" the crank journals within them. The reason for the "soft(ish)" layered alloys is not for their "slipperiness"... rather so it doesn't destroy the crank when the bearing fails.

I think the engine bearing material is porous so as to hold oil in the pores, otherwise, you would wipe out a crank evertime you started the engine.

[Bullshop]

I wonder why all the listed pressures for the SFT jacketed bullet are all the same at 52,600.
On the first load with the cast boolit on the max load what does the C after the charge weight represent?

[RobS]

C probably stands for compressed load which is interesting as the Cast Performance PB boolit is looking like it takes up more case volume vs the Swift Jacketed bullet since they have the same max charge yet the cast boolit is seated to a longer OAL. I assume the H110/296 load is what they determine as the same since they are only different by lot number (same powder company makes both), the same thing they do with their HP38 and Winchester 231 info. As to why the max charges for the LilGun and 4227 being 52,600..............beats me.

[JonB_in_Glencoe]

Yes, I said that and since that post I have been convinced, by those with Pressure Testing Equipment, that with "All things being equal a lead bullet will generate higher pressure than a jacketed bullet".

Figured the thread could have some more data. I'm not saying one way or the other as it's been tested with labs to show both an increase in pressure/velocities with cast bullets, however not all cast bullets are the same. I know this data is formed with the use of Cast Performance Cast Bullets and their BHN as stated on their site is 18-21 BHN. Other data could have been used with softer bullets, swaged bullets, who knows and there in lies more variables to load data that is published by companies that use pressure testing equipment.

Oh My,
Look at THAT Data. More powder with the CB loads yields similar or higher velocities and less pressure
Heck...Hodgdon's pressure meter must be out of calibration

All things can not be equal.

[steve4102]

 BULLET WEIGHT
250 GR. LYMAN CAST
Starting Loads Maximum Loads
Manufacturer	Powder	Bullet Diam.	
C.O.L.
Grs.	
Vel. (ft/s)
Pressure
Grs.
Vel. (ft/s)
Pressure
Hodgdon	H322	.376"	2.500"		24.0	1,534	22,500 CUP		27.0	1,692	27,600 CUP
Hodgdon	H4198	.376"	2.500"		18.5	1,408	17,100 CUP		24.0	1,740	26,200 CUP

 BULLET WEIGHT
255 GR. BAR JFP
Starting Loads Maximum Loads
Manufacturer	Powder	Bullet Diam.	
C.O.L.
Grs.	
Vel. (ft/s)
Pressure
Grs.
Vel. (ft/s)
Pressure
Hodgdon	H322	.375"	2.620"		27.0	1,603	25,500 CUP		33.0	1,830	28,200 CUP
Hodgdon	H4198	.375"	2.620"		24.0	1,554	21,400 CUP		28.0	1,788	26,700 CUP

This data is from Hodgdon.

Note the Lead bullet used 4gr LESS of H4198 and 6gr LESS 322 to achieve similar pressures.

I would take a screen shot, but I don't know how.

[DrCaveman]

How about this:

What the **** does this whole supposition matter?

You load to book standards, or you generate your own loads based on experience and knowledge of pressure signs. You judge accuracy by where your boolit hits compared to where you aimed, and you judge performance on targets. You then record actual velocities obtained, and if you have the equipment, pressures. Who cares if the pressures are higher or lower if the boolit is performing well?

[Whitespider]

I think the engine bearing material is porous so as to hold oil in the pores, otherwise, you would wipe out a crank evertime you started the engine.

Technically correct... sort'a... "porous" ain't quite the correct terminology.
But that's another discussion...
*

[singleshot]

 BULLET WEIGHT
250 GR. LYMAN CAST
Starting Loads Maximum Loads
Manufacturer	Powder	Bullet Diam.	
C.O.L.
Grs.	
Vel. (ft/s)
Pressure
Grs.
Vel. (ft/s)
Pressure
Hodgdon	H322	.376"	2.500"		24.0	1,534	22,500 CUP		27.0	1,692	27,600 CUP
Hodgdon	H4198	.376"	2.500"		18.5	1,408	17,100 CUP		24.0	1,740	26,200 CUP

 BULLET WEIGHT
255 GR. BAR JFP
Starting Loads Maximum Loads
Manufacturer	Powder	Bullet Diam.	
C.O.L.
Grs.	
Vel. (ft/s)
Pressure
Grs.
Vel. (ft/s)
Pressure
Hodgdon	H322	.375"	2.620"		27.0	1,603	25,500 CUP		33.0	1,830	28,200 CUP
Hodgdon	H4198	.375"	2.620"		24.0	1,554	21,400 CUP		28.0	1,788	26,700 CUP

This data is from Hodgdon.

Note the Lead bullet used 4gr LESS of H4198 and 6gr LESS 322 to achieve similar pressures.

I would take a screen shot, but I don't know how.

Look again. The longer COL for the jacketed EASILY accounts for the discrepancy.

[singleshot]

Put another way, unless the projectile is seated into the lands, longer COL (cartridge overall length) will result in lower pressure.

[Whitespider]

Do ya' suppose that possibly... maybe... could it be that it ain't as simple as some of y'all wanna' believe it is??
I mean... just throwin' this out... suppose ya' compare a jacketed to a cast and start with low powder charges/pressures. Suppose those low charges ain't enough to obturate the bases of either. Now, as you work up the charge/pressure one base does begin to obturate (who knows which?), and further up the ladder the other does... what do you suppose the pressure comparisons will look like at those different points?? What happens to pressure when acceleration gets to the point where the cast begins to actually slump?? What if it runs short of lube at some point in the barrel?? Does barrel condition (pitting, roughness, etc.) affect the friction coefficient of one more than the other?? Rate of twist?? Free bore and lead angle of the lands??

This discussion has reached the point where no more value can come of it... there's been multiple examples shown where somebody's load date supports one side or the other of it. OK... I get it... or, at least I think I do. Something during testing prompted Western Powders to believe, at least as a general rule, that cast (of like weight) will generate higher pressures at identical powder charges in the barrels they tested (and there's similar statements in the Lyman, and other manuals). But at the same time, every manual I've ever read also states, even warns, there are no hard-fast set rules... every gun is a law unto itself, and variances in reloading technique alone can negate any "general" rule established by anyone (and that includes Lyman, Western, and whoever else).

I know I've seen it go both ways... using typical "observational" evidence as a reloader and amateur (very amateur) ballistition. I don't believe Western stated that as an always, without exception, hard-set fact... heck, even I know better than that...
*

[RobS]

Do ya' suppose that possibly... maybe... could it be that it ain't as simple as some of y'all wanna' believe it is??

I know I've seen it go both ways... using typical "observational" evidence as a reloader and amateur (very amateur) ballistition. I don't believe Western stated that as an always, without exception, hard-set fact... heck, even I know better than that...
*

Exactly and what I mentioned from my beginning post with the variables.....to many examples that support both causes because both exist and labs have proven this as the data is there. People can state whatever they want however fact is there in both directions concerning cast bullet/jacketed bullet load data comparison and there is no absolute and making a statement that is one sided is refuted or supported with lab tested data. It is all there folks.

[Bullshop]

So I have to ask, has any of this changed anyone's mind from what it was regarding this subject before this thread started?
My guess is I think not.

[RobS]

So I have to ask, has any of this changed anyone's mind from what it was regarding this subject before this thread started?
My guess is I think not.

Not mine but then again I seen it from both accounts from the beginning and stand by the fact there is no definable absolute other than proven lab pressure data which of course can be taken into account at each particular lab with such utilized firearm, loaded ammunition and pressure testing equipment.

[BAGTIC]

Compare the Lil Gun loads. It takes 3 grains more powder to achieve essentially the same velocity with the cast aswith the jacketed and it did so with much less pressure.

What we need to see is an identical load with both bullets with the bullets seated to the same depth producing same usable case capacity. There may still be some difference because different ogives will produce differences in bullet travel prior to engaging riflings but that is probably the best that can be done without firing one series from the gun and then modifying its throat for the second series.

[RPRNY]

This has been resolved....several times during this thread. Clearly Western Powders' general statement is incorrect. All other things being equal.... except we have established beyond all reasonable doubt that all other things are never equal.

[Digital Dan]

Y'all lemme know when it's all figured out.

[MtGun44]

And it may be useful to note that those Cast Perf boolits are typically harder than
the hinges of hades, so likely on the high end of boolit pressures.

Bill