Cast vs jacketed pressure?

[Mr_Flintstone]

This has probably been answered somewhere, but I can’t seem to find it anywhere. How is cast bullet pressure related to comparable size/weight jacketed bullets? Checking my manuals, it seems to be a hodgepodge of sometimes seemingly contradictory data. Sometimes when the same amount of powder is used in cast and jacketed loads, the cast bullet is faster with less pressure. Sometimes cast is faster with more pressure, sometimes slower with more pressure, and sometimes they are about the same. What gives here? I’m talking same caliber, same manual, same powder; not across multiple manuals.

I always thought that cast bullets had less friction, and would produce higher velocities with less pressure than jacketed, but I guess not always.

[Larry Gibson]

"it seems to be a hodgepodge of sometimes seemingly contradictory data."

The data, while seemingly contradictory, is actually correct. Since the last time this topic came up I have endeavored to resolve the answer one way or the other by pressure testing numerous cartridges with the same load and bullet weights but with jacketed vs cast bullets as the question. I can say without a doubt from what I've learned is that there is no clear cut answer.

Before conducting considerable pressure testing to find an answer, I was of the opinion, based on previous readings, that the cast bullets would give less pressure given an identical load. But I found out, as mentioned, it just is always so. I'm now of the opinion, based on my own pressure testing, that the pressure variance is more likely attributable to seating depth, hardness of the alloy, hardness of the jacket, hardness of the jacketed bullet core and bearing length of the bullets.

Bottom line is; don't bet on a jacketed bullet of equal weight than a cast bullet giving more pressure with a given load. It might, then again, it might not........

[Mr_Flintstone]

Thanks Larry. You always seem to have the answers I need.

[Mal Paso]

Thanks Larry! I was wondering what happened with your tests.

[TjB101]

Great feedback and topic

[gumbo333]

To Larry G, when you find that the pressure is higher with the cast boolit, is it close to the jacketed pressure? Any dangerously higher? This very interesting. Thank you.

[pcmacd]

To Larry G, when you find that the pressure is higher with the cast boolit, is it close to the jacketed pressure? Any dangerously higher? This very interesting. Thank you.

I have read over and over by "professional" gun writers that jacketed rounds create more pressure than do cast loads.

~~~~~
Don't believe everthing you find in the Lyman Cast Bullet Handbook.

I've shot very hard, gas checked cast bullets of 30 caliber in Garands, M1 Carbines and Russian SKS w/o any issues at all -- at full tilt "jacketed" loads and velocities, in bullets I cast myself of range salvage and lots of foundry type. No leading. No issues at all.

I shoot hard cast gas checked bullets of the same formula in my 44 mag 629. I had never cleaned the weapon after about a thousand rounds. A Teslong bore scope inspection last week showed just tiny amounts of lead in one portion of the barrel. Ran the Lewis tool down it, removed half, and I am not worried about the rest.

A couple of jacketed rounds down the tube would probably have worked better.

I mean, seriously? A thousand cast lead gc rounds down the 629 bore, and just a little lead? And no crazing just north of the leade? The barrel looked new.

These were FULL TILT BOOGIE loads, 22.3* (perhaps more, the recommended and only load for 296, mag primer) grains of H110 or 296 on a ~240 grain hard cast Lee gas check bullet... using exactly the same load you would use for a jacketed round.

*My propellent was actually WC820, a virgin (not pulldown) surplus propellent intended for the 30 carbine. It is H110/W296 but not "canister grade"; this lot is likely a little slower than canister grade , so perhaps I put a bit more in the load than the books called for to get the same velocity published for canister grade propellent according to an Oehler.

Use a LOADING MANUAL! This load works great in my guns, but might be dangerous in yours!! Use your freakin' heads, dudes.

[44Blam]

I have read over and over by "professional" gun writers that jacketed rounds create more pressure than do cast loads.

~~~~~
Don't believe everthing you find in the Lyman Cast Bullet Handbook.

I've shot very hard, gas checked cast bullets of 30 caliber in Garands, M1 Carbines and Russian SKS w/o any issues at all -- at full tilt "jacketed" loads and velocities, in bullets I cast myself of range salvage and lots of foundry type. No leading. No issues at all.

I shoot hard cast gas checked bullets of the same formula in my 44 mag 629. I had never cleaned the weapon after about a thousand rounds. A Teslong bore scope inspection last week showed just tiny amounts of lead in one portion of the barrel. Ran the Lewis tool down it, removed half, and I am not worried about the rest.

A couple of jacketed rounds down the tube would probably have worked better.

I mean, seriously? A thousand cast lead gc rounds down the 629 bore, and just a little lead? And no crazing just north of the leade? The barrel looked new.

These were FULL TILT BOOGIE loads, 22.3* grains of H110 or 296 on a ~240 grain hard cast Lee gas check bullet... using exactly the same load you would use for a jacketed round.

*My propellent was actually WC820, a virgin (not pulldown) surplus propellent intended for the 30 carbine. It is H110/W296 but not "canister grade"; this lot is likely a little slower than canister grade , so perhaps I put a bit more in the load than the books called for to get the same velocity published for canister grade propellent according to an Oehler.

Use a LOADING MANUAL! This load works great in my guns, but might be dangerous in yours!! Use your freakin' heads, dudes.

I use 23.5 grn W296 on an Accurate 43-240 AG gas checked boolit. This is pretty much a full case, is not sooty and it is also a very accurate load. These also go about 1450 fps in a 7.5" barrel. I powder coat and have shot tens of thousands of those rounds in my Ruger Redhawk. I have had ZERO leading.
It was a long time ago when I came up with this load and I remember taking all my books out and looked at all different kinds of data and ended up having a ladder and took my powder and my little hand press to the range. That load was the best burning and most accurate that I tested on THAT day.
Turns out, my Henry also likes this load and I've been able to consistently hit 2' targets at 300 yards with it.

[243winxb]

Some data -Pressure- Cast vs Jacketed -Winchester Data Some powders are discontinued. 1996

[Larry Gibson]

To Larry G, when you find that the pressure is higher with the cast boolit, is it close to the jacketed pressure? Any dangerously higher? This very interesting. Thank you.

Dangerous? Kind of depends on what anyone's idea of "dangerous" is......

A couple examples;

357 Magnum
Winchester brass cases
WSP primers
7 gr Alliant Unique
Cast bullet alloy; COWW + 2% tin AC'd, BHN 13-14
All bullets seat to crimp groove with medium crimp
SAAMI MAP; 35,000 psi

Speer 158 SP; 32,500 psi
Lee TL358-158-SWC seated to 1st lube groove; 33,000 psi
Lee TL358-158-SWC seated to 2nd lube groove; 29,600 psi
Lyman 357156 seated to 1st crimp groove; 32,200 psi

44 Magnum
Winchester brass cases
WLP primers
21.2 gr Alliant 2400
Cast bullet alloy; COWW + 2% tin AC'd, BHN 13-14
All bullets seat to crimp groove with medium crimp
SAAMI MAP; 36,000 psi

Hornady 240 XTP; 38,400 psi
Laser Cast 240 SWC; 35,000 psi
Lyman 429244 258 gr; 36,300 psi
Lyman 429360 243 gr; 36,400 psi

With 9.5 gr Alliant Unique

Hornady 240 XTP; 29,200 psi
Laser Cast 240 SWC; 25,900 psi
Lyman 429244 258 gr; 26,700 psi
Lyman 429360 243 gr; 26,000 psi
Lee TL430-240-SWC; seated to 1st lube groove; 28,300 psi

Note; A recent test of 3 consecutive 10 shot groups of the same load (21 gr Alliant 2400 under the RCBS 44-250-K) gave a 2,100 psi test to test variation of the average pressure. That is normal and within expected test to test variation. In the 357 magnum one cast bullet load exceeded the jacketed bullet pressure. The Lee bullet is seated deeper than the jacketed. In the 44 Magnum all the cast bullets gave less psi than the jacketed but still were very close to each other. Were I to run the tests again the results may very well be different considering the variables previously mentioned along with test to test variation and lot to lot variation of components. Probably why SAAMI lists not only the MAP but also acceptable levels of pressure; the Maximum Probable Lot Mean (MPLM) and the Maximum Probable Sample mean (MPSM) for any lot of loaded ammunition. Listed pressures by SAAMI, CIP, any manual or those arrived at by a computer program are not "finite".

Thus in comparing psi from jacketed bullets compared to equal weight cast bullets listed in any publication one must be aware of the probable test to test variation. Not knowing how many tests the psi results listed in a manual are based on making a comparison is simply guess work. As I recall, in every manual I have read over the last 50+ years they have all stated not to assume a maximum listed load is "safe". They all state to work up to those loads and back off if any sign of excessive pressure arises. That is excellent advice and should be adhered too.....

[onelight]

Thanks for posting that Larry . Interesting to see how close the jacketed and cast pressures compare . It appears that seating depth has a lot more impact than if it is jacketed or not.

[243winxb]

Bullet leads analyzed from CCI, Federal, Remington, and Winchester have contained up to 0.42 percent arsenic, 6.8 percent antimony, 2.5 percent tin, 0.2 percent bismuth, 0.22 percent copper, 0.031 percent silver, and 0.011 percent cadmium. The wide ranges in concentrations of all of these elements within sources provide for thousands of distinguishable melts of bullet lead at any one time.

[Larry Gibson]

Thanks for posting that Larry . Interesting to see how close the jacketed and cast pressures compare . It appears that seating depth has a lot more impact than if it is jacketed or not.

That seating depth is probably the most important factor is, more and more, what I am coming to believe is the most deciding factor/variable.

Also many, if not most of us [myself included], were led to believe by the written gospel of many writers/experts that posted pressures were finite and written in stone not to be disagreed with. The more pressure testing I do the more I find it just isn't so. That is still no reason to discredit those published figures as they usually give us a safety margin. I do still use them as reference myself when working up test loads. I advise against ignoring them though as I do not, even though I can pressure test with many cartridges.

[243winxb]

In general , Lead produces more velocity, with less pressure & less powder.

More bang for the buck.

[Larry Gibson]

In general , Lead produces more velocity, with less pressure & less powder.

More bang for the buck.

Perhaps "in general"...…maybe.....

In the above three posted loads the 357 cast bullet loads were all higher than the jacketed. In 44 magnum the 2400 load gave considerably higher velocity than any of the cast loads. In the 44 magnum Unique loads the jacketed bullet velocity was within the range of the cast bullet velocities with 61 fps separating all 5 loads velocities.

[gumbo333]

Thanks Larry G. I should have used a different word rather than "dangerously ". But you answered my question. I was only inquiring anyway just for my own knowledge, since lately I have enjoyed exploring mouse fart loads . Now I need to take care that my boolits exit my barrel and that I use slow safe reloading habits. But I certainly love reading these posts of what others are doing and what they discovered. Thank you all.

[44magLeo]

Larry Gibson, Have you done pressure tests on rifle cartridges comparing lead to jacketed, as in 308, 30-06 and such.
Leo

[Larry Gibson]

Larry Gibson, Have you done pressure tests on rifle cartridges comparing lead to jacketed, as in 308, 30-06 and such.
Leo

Limited testing with 30-30, 308W and 45 -70 …. nothing conclusive one way or another...…….

[bpatterson84]

I think the pretty clear answer here is seating depth, which in regular practice, is not the easiest dimension for the handloader to come across. Its simple, there's an expanding gas in a pressure vessel, and its volume matters tremedously. Now yes, cast and coated bullets pass down the bore easier if sized appropriately, but nothing matters more than that intital container volume. Pressure will never be higher than slightly after the bullet starts moving, the container is expanding at that point, and the gas volume wont keep up, thus a pressure drop and why port pressures are no where near chamber pressures. I cant concieve of a more important variable.

[Mr_Flintstone]

I have a very old manual that gives seating depth of bullets rather than overall cartridge length. Most modern manuals give OAL for various loads with only 1 bullet; often times of unknown dimension. Seating to the crimp groove doesn’t always do it right either. I have a bunch of 158 gr .357 bullets of various types that vary a great deal in distance to the crimp groove. I don’t worry about these in .38 Special or light .357 mag, but it makes me nervous on some of them with heavy .357 magnum loads. I wish manuals would list the seating depth of the bullet they are testing, but I guess that’s just wishful thinking.