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

[hickfu]

I read this while lubing some boolits so I grabbed my reloading manual (Lyman 49th) and picked a caliber I reload for... 45-70

500gr Jacketed bullet: 49gr H322 = 1673fps 36,5000 CUP
500gr lead boolit: 51gr H322 = 1753fps 36,7000 CUP

Seems to me that if I used 49gr of H322 on the Lead boolit it would have a lot less pressure.
46gr of H322 = 24,700 CUP

Doc

[deltaenterprizes]

The pressures listed in the LEE Reloading Manual for 40 S&W with a 180 TC boolit & bullet show much lower pressure for the lead boolit.

[dragon813gt]

So the shot start initiation pressures that QuickLoad uses are backwards. Good to know and I will adjust the program accordingly.

[rking22]

well, now I have NO confidence in anything from Western Powders! Didn't know they sold bullets ,so can only assume they didn't bother to actually use that fancy test equipment to determine their answer , just took a swag and threw in some teck terms to support their guess. Think someone should request an actual pressure trace for 2 170 gr 30 cals in a 30WCF , Wonder if hey would do the test?

[DeanWinchester]

Heck, I'm dummer than a bag of hammers but I have chrono'd equal weight bullet/boolit [9mm] with the same powder charge and ALWAYS got lower velocity from the cast boolit. I was laboring under the delusion that low velocity and low pressure kinda held hands every once in a while.

[Grump]

I beg to differ on the thought that this is a *universal* effect.

I did book-lernin' research like 20 years ago when .40 S&W kB! events were popping up in Glocks shooting lead bullets, and actually collected an eyewitness account of one going to case failure and shattering the grip while inflating the magazine and dumping the unfired rounds on the ground. Report was it had gone about 700 rounds of lead without cleaning...

Anyway, Winchester's manual back then showed lower charge weights with similar velocities and pressures with lead bullets compared to jacketed of same weight--most of the time. Differences AFAIRemember were anywhere from zero to 7% less charge weight for the lead loads.

This was across several calibers, though I was paying the most attention to .40 S&W, 9mm and .357 Mag at that time.

My own experiences tend to bear this out, at least at higher pressures. Jacketed and plated 125s in the .357 tend to burn the powder the same, but Oregon Trail 125s at BHN 22, and some of our own cast ones at BHN 14-16, showed flatter primers and a bit more velocity than the others. This was with Win 296, Alliant Power Pistol, and maybe with Win 231. Might have even seen it with Unique or Herco, but I don't remember for sure and the notes are where I don't want to go right now.

All three bullet types had pretty much the same bearing surface and were all loaded to the same OAL/intrusion into the powder cavity.

With so many citations to published rifle caliber data and personal rifle experiences, I wonder if the effects I observed are reversed with somewhere more than 7-10 inches of barrel being involved, as far as velocities effects go. Chamber pressure drops so fast I would expect there to be no differences between rifles and pistols using the same cartridge.

[44man]

Might make a good "sticky in the funny department!"

[DeanWinchester]

There is a good side to BS like this. It scares away the sheeple. Leaving the lead for the rest of us.

[fredj338]

Heck, I'm dummer than a bag of hammers but I have chrono'd equal weight bullet/boolit [9mm] with the same powder charge and ALWAYS got lower velocity from the cast boolit. I was laboring under the delusion that low velocity and low pressure kinda held hands every once in a while.

Exact opp for me. With any handgun caliber, any powder, I always get higher vel with lead bullets with equal charge wts. Since there is no free lunch, all things being equal, higher vel = higher pressures. The idea a lead bullet offers less friction would be the opp in pressures. Look at any data, or check your own, slippery bullets, like moly, need higher charge rates to get sim vel as non coated???

[waksupi]

Cast are slicker than jacketed, so produce more velocity with less pressure.

[DeanWinchester]

Hmmm, I'll go dig out my load book and see what I wrote down.
I know it was AA#5 with a 124g FMJ and a 125g Lee RN. I'm right certain velocity with the cast was lower but it's not like it'd be the first brain fart I ever had.

[DeanWinchester]

Alright. Let this be a lesson to myself and everyone. Meticulous record keeping is pretty important.
I've got wrote down that a 124g FMJ in Win case and 5.5g of AA#5 averaged 1060FPS and 125g Lee [same case, charge and primer] averaged 960fps. My lyman manual begs to differ. OBVIOUSLY, I wrote it down assbackwards.....but I distinctly remember remarking to guys at the range that it seemed strange and jotted it down in my book as such.

Does this win me the idiot of the day award?

[Bullshop]

Hand gun rounds are going to be effected by the depth of the base of the bullet in the case there by effecting the case volume. Many cast boolit designs will have the base of a seated boolit farther out or up the case than a jacketed bullet of the same weight. In small volume cases this will have a very significant effect on pressure. Same case, projectile weight, powder and charge, primer, but different internal volume for the different projectile types. Rifle rounds will not to any significant degree be effected by such a difference in seating depth.
In my experience I am sticking with my first assertion but specifically referring to rifle rounds with at least mid size volume like a 308.

[Whitespider]

I'm gonna' call everyone of ya' on this...
Higher pressure equals higher velocity only if all else remains equal... change projectiles, even of the same weight, and all bets are off.
Comparing cast to jacketed, based only on weight, is not possible.
Y'all should go to the Hornady reloading center and play around some... there ain't no set "rule" relating to pressure, velocity, or anything else.
Here's some examples from the website...

.38 Special
125 gr. HDY XTP - 6.0 grs. SR4756 - 1046 fps - 16,400 psi
125 gr. cast swc - 6.0 grs. SR4756 - 1091 fps - 16,100 psi (same powder, higher velocity, lower pressure)

125 gr. HDY XTP - 6.3 grs. CFE - 1133 fps - 16,000 psi
125 gr. cast swc - 6.2 grs. CFE - 1201 fps - 16,100 psi (less powder, higher velocity, higher pressure)

125 gr. HDY XTP - 6.2 grs. AutoComp - 1068 fps - 16,500 psi
125 gr. cast swc - 6.2 grs. AutoComp - 1139 fps - 10,800 psi (same powder, higher velocity, lower pressure)

158 gr. HDY XTP - 10.0 grs. H4227 - 864 fps - 15,500 cup
158 gr. cast swc - 10.0 grs. H4227 - 983 fps - 15,700 cup (same powder, higher velocity, higher pressure)


.44 Magnum
240 gr. Nosl JHP - 10.0 grs. Tightgroup - 1292 fps – 37,700 cup
240 gr. cast swc - 10.0 grs. Tightgroup - 1288 fps – 38,400 cup (same powder, lower velocity, higher pressure)

240 gr. Nosl JHP - 11.0 grs. HP38 - 1272 fps – 37,800 cup
240 gr. cast swc - 11.0 grs. HP38 - 1288 fps – 38,400 cup (same powder, higher velocity, higher pressure)

240 gr. Nosl JHP - 10.2 grs. Universal - 1246 fps – 38,200 cup
240 gr. cast swc - 10.2 grs. Universal - 1276 fps – 37,500 cup (same powder, higher velocity, lower pressure)

[JonB_in_Glencoe]

All things CAN'T be equal !

It's kinda like saying this...All things being equal, If a ship and a train have the same size engine, A train can haul more freight than a Ship, because the water creates more friction against the steel hull of the ship, than the train's steel wheels on steel rails.

[Bullshop]

On the examples you have given there is no indication as to where the bullet base is. To be an equal comparison with hand gun rounds the case volume has to be equal. If one is deeper seated than the other that in itself will effect the pressure.
In order to have an apples to apples comparison it is critical that the bullet bases be seated to the same depth in the case or all bets are off.

[Whitespider]

...try pushing a jacketed bullet through a barrel and compare that to a lead one.

Lead does have a higher frictional co-efficient than copper... but copper resists deformation more than lead.
If you don't believe lead has a higher frictional co-efficient try this simple test...
Take a pair of lead ingots of the same size, glue a piece of sheet copper on one flat of one ingot, place them on a piece of plate steel (copper down)... now slowly raise one edge of the plate and see which ingot slides off first.

You can't push a bullet made of ice down the bore either... would you say ice has a higher frictional co-efficient than lead??

[Whitespider]

All things CAN'T be equal !

I didn't say "all things", I said "all else".
In other words, the same bullet will gain velocity if pressure is increased (by increasing the powder charge)... but the same can't be said if two different bullets are used. You can't expect two bullets of same weight but different construction (construction may mean material, shape, bearing surface, or any number of other things) to achieve identical velocities just because pressure is identical... one or the other is likely to go considerably faster.

Pressure is only relative to the same bullet... not two different bullets.

[MtGun44]

NO - lead does NOT have a higher coefficient of friction than copper when lubricated against smooth steel, it is lower. This is why the bearings inside your engine in your car have LEAD ALLOY on the surface.

Bill

[Whitespider]

NO - lead does NOT have a higher coefficient of friction than copper when lubricated against smooth steel, it is lower. This is why the bearings inside your engine in your car have LEAD ALLOY on the surface.

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.