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

[Peregrine]

Thanks for the update Larry, that greatly exceeds my expectations for testing and i'm pretty excited to see your results. I hope you get good data, good luck!

[longbow]

I'll second what OS OK said... I'd be happy to help out too but the commute is a killer! There is a selfish side to that thought too ~ your bad weather is better than our good weather, currently anyway. It is -2° C outside and raining so the roads are iced up and slick! I would definitely rather be running around on a gun range in Arizona than driving to work in this! Then blowing snow off the driveway for the second time today!

In any case, thanks for doing this and I look forward to your results.

Longbow

[DGV]

Has anyone had the misfortune of a stuck jacketed bullet in a barrel? How about a stuck Lead alloy bullet? Which was easier to move?

[fredj338]

In my experience all else being equal a cast lubricated boolit will give lower velocity of in the neighborhood of 150 fps depending on the type of load and cartridge.
Since I can not accurately measure pressure but can accurately measure velocity I use velocity as an indicator of pressure.
In my own observations lower velocity reads as lower pressure.
Another point I would like to make is this if a jacketed bullet has less friction resistance in its passage through a barrel why then do we not use jacketed bullets to slug our barrels?

I have NEVER had a lead bullet give less vel than jacketed of the same weight, any caliber, with identical powder charges & near identical OAL. Lead bullets always have produced higher vel. If there is less friction, less pressure, less vel, Unless you add more powder to drive the bullet faster. You see this in data for moly coated jacketed, I see no reason to think it is diff with lead.
The slugging thing, not friction but malleability. A lead bullet will more easily be deformed as it is pounded down a barrel. Why they call for nearly dead soft lead & not one of lino.
I would love to see pressure testing done but what is really needed would be dear identical bullets in lead & jacketed for the best comparison. I do know that when I substitute a solid coated bullet vs a coated bullet with a grease groove, my vel go up. Same bullet wt, but more bearing surface in the bullet with no groove. What does that tell me, higher pressures. A proper sized lead bullet seals the bore better, no gas leaks that may occur with jacketed. My theory, love to see real data though.

[Larry Gibson]

Appreciate all the offers of help, I sure could use some but I know many of you would if you could. Ran into a technological problem today......I always charge up the battery in the M43 PBL the night before testing so I plugged it in night before last. Would not hold a charge....... Pulled it out and the date I put on it when I last replaced it was May of '09 .......where does the time go? Anyways, have a new one ordered but won't be here till next Thursday.....

DGV

I've removed numerous stuck bullets, jacketed and cast, from barrels over the years. The cast has always been much easier to remove.

[unique]

One question for Larry. What are the BHN's for the lead bullets?

The following are my thoughts and experiences for the 357 Mag. The softer the lead the higher the expected pressure. Starting with a properly sized cast lead bullet and near max loads, my experience in 357 Mag shows crossover around BHN 18 meaning a cast lead with BHN > 18 will have pressure/velocity close to a copper jacketed bullet.

The reason is the lead bullet has a lower cofficient of friction than a copper jacketed but the higher BHN cast lead 'leaks' more gas than the lower BHN. The other parameter at work is the powder itself as it can burn non-linear as function of pressure. Soft lead -> better seal -> quicker powder burn.

Hypothetically speaking a perfect sized cast lead relative to the bore would have perfect seal. This is not the case in reality as there is always some amount of gas leak past the bullet. This parameter overrides the friction coefficient in many cases for the 357 Mag.

As you well know, there are no absolutes since ballistics parameters can vary & interact . Thank you for your time. effort, and resources in running these tests!

[Larry Gibson]

Yes there are absolutes, they are called the laws of physics. You can indeed vary the parameters but the results, even though they may be different, will still be within the laws of physics. If we really stop and think about it there are many "absolutes". The problem we have is many think there are no absolutes (that statement contradicts itself because it is an absolute statement in and of itself) which gives them a means of rationalizing their own concepts w/o adequate proof or a realization of what is actually occurring. How many times did your grammar teacher tell you the rule is; "Never is never the subject of a sentence". Well, in that sentence "never" IS the subject of the sentence. That contradicts the absolute. Rules are not laws. There are "exceptions to the rule" which lend the perception to some that "there are no absolutes". The fact is there are not exceptions to the laws of physics. At least not here on earth. Today we can not send astronauts to the Sun because they would burn up. The laws of physics tell us that. Perhaps they will figure how to get around that absolute by going at night.........

Seriously, I also would assume, at this stage, that a higher BHN cast bullet would give a higher pressure given the same load. However, if we use the same mould to cast bullets of various BHNs and then pressure test with the same load we introduce another variable.....the weights of the bullets will be different because of the different compositions of alloy. We could mitigate that by using a single alloy and heat treating the bullets to different BHNs. Should you wish to undertake that task let me know, perhaps we can arrange a test? Keep in mind a published psi is almost always an "average", just like published velocities. There is always an ES (Extreme Spread) of any single test. Multiple tests of the same load will also result in an ES of their averages of both psi and velocities. Many times small variations can make such a small change, if any, that the change will fall within the ES of the test and thus be meaningless.

The OP's question and what I am testing is if we simply substitute an equal weight cast bullet for a jacketed bullet will the pressure be higher or lower than the jacketed bullet load's pressure. When you see the results of the test you will see I use several different cast bullets of different alloys (BHNs) of equal or very close to equal weight in a couple of the cartridges. As to whether the change in bullets from jacketed to cast given the same load will be meaningful remains to be determined by actual testing instead of hypothesizing. I prefer to test to find what really occurs vs hypothesizing and think the results could prove interesting.....whatever the actual test results are.

[tazman]

Larry-- It sounds as if some people are trying to set up things with supposition, so they can claim your results are wrong or at least not realistic.
I will wait for the results and see what turns up. I have seen tests you have run before and I will accept your results.

[Larry Gibson]

Tazman

Does seem that way..no problem, just human nature. It's difficult to counter precepts we've come to believe......was for me anyway. In the last 12 to 15 years I've revised my thinking on a lot of things with cast and jacketed bullets from things I'd been led to believe as read in books and magazines. Actual testing has proven many of those precepts incorrect or blatantly false.

I've stabbed a lot of sacred cows on this forum and several others. Been banned on a couple including this one. It's unfortunate that some take it as a personal affront when we learn from actual test results that our preconceived concepts are not correct. As I said I had a real problem accepting some of it myself as I always thought the "famous" writers were the "experts" and what they said was written in stone.....right? Well I found out maybe not, maybe they weren't correct and their ideas were simply based more on assumptions than actual test results.

I've come to realize that admitting one's concepts are not correct per say based on results from actual thorough testing isn't a negative reflection on one's self, it's actually a positive reflection. Unfortunately some don't see it that way and refuse to consider anything that may contradict what they've stated or believe....and that's ok.....I've gotten used to it here and just keep trying to further explain what I've learned from factual test results. Sometimes it's accepted, many times not. Yes, I have changed my mind or modified my ideas on many things the last 12 - 15 years in this game. It's called ......learning.....

As I said I don't really know the answer to the OPs question. I am seeking to find the answer though. We shall see.

[unique]

Wow, I suggest something to consider for your test and get a blast of hot air running the gamut from laws of physics, my grammar teacher, something about a supposition, murdered cows, and what comes across as a need for understanding and empathy.

I sure got a lot to think about...

[JSnover]

I doubt hard cast would provide the same resistance as a copper jacketed bullet. Even if you got close I imagine there would be enough of a difference to get valid results.

[Larry Gibson]

Unique

All that was a conversation in general regarding numerous post. As I said I no longer mind the discussions. Yours was a specific question regarding BHN......a good question btw. It's one that may or may not be answered in my test. My current test will compare bullets of COWW against the much higher BHN Laser Cast bullets of the same weight/caliber/load. If that doesn't answer that question then a better test might be as mentioned?

[Mal Paso]

When 300 MP first came out, Alliant's load for the 240g Speer GDSP was 25g for 1570 fps from an 8 inch test barrel. I was getting a Lot less velocity than I expected even with a shorter barrel. Ben at Alliant suggested it might be because I was shooting cast. So I did a side by side test, same brass, same Fed 150 primer they used, in a 4" Ruger Redhawk. 6 shot strings.

The .431" 250g NOE 429421 ran 1306 fps

The 429" 240g Nosler JHP ran 1235 fps

The powder was out of it's useful range, but I'll bet on lead being faster. You would think lower pressure ...

[Walkingwolf]

From my own experience with lubed cast bullets is they use less powder for similar velocity, PC coated cast take even less powder. So I gather from their claims that less powder means more pressure.

[JBinMN]

I have the test rounds loaded. They are in;

357 magnum
44 Magnum
30-30
308W
45-70

There are 280 test rounds loaded in 28 tests. There are 14 loads with jacketed bullets and 14 identical loads with cast bullets. A couple of the cast bullets used weigh a few grains more than the jacketed counterpart but they are all close. A complete description of each load will be in the test result report. I will probably start a new thread with that test result.

That will take 8 - 10 hours of testing given; set up, shooting, target changing, entering data in the computer, barrel cleaning, the usual range interruptions, changing firearms, etc.. I am not sure I will get it all done in one test session. If not then each test of a given load with both jacketed and cast will be conducted back to back to keep the conditions as close to the same as that is the comparison we are looking at; the pressure difference between the same load with jacketed and cast bullets of equal weight.

Next I'll enter all the load data into the Oehler M43's program test format in the laptop (part of the system) I use at the range. I am watching the weather forecasts for a good day and potentially a good day following. I'll report back with the results when the test is complete.

Mr. Larry Gibson,

A similar subject was being discussed & I mentioned this topic & your posts here to be checked out for more info.
http://castboolits.gunloads.com/show...Lead-vs-jacket

In re-reading this topic, I do not see the results of the testing, and I am thinking that you posted those results elsewhere in the forum, but am not sure. While I will search a bit to try to find those results, if you happen to see this post and can point me (& any others who might be searching) in the right direction to find those results, in case I don't find those results to post a link here to them, and as well in that other topic, I would appreciate it.

[swheeler]

Yah, I didn't see the results either? Maybe they didn't come out like he supposed, so he never posted them!

[Larry Gibson]

Yah, I didn't see the results either? Maybe they didn't come out like he supposed, so he never posted them!

Nice try...........

Reason could be as simple as I haven't finished the test........

[swheeler]

I hear ya Larry, that old age slows a guy waaaaaaay down

[JBinMN]

Nice try...........

Reason could be as simple as I haven't finished the test........

Thanks for clearing up my efforts to find the data& why I was not finding it.

G"Luck!, if ya ever get a chance to do the testing.


Please post up what ya find if/when ya do.

[Larry Gibson]

JBinMN

As you've seen on other topics I have posted results of recent and past tests. Those results have been what they were, not what I wanted them to be. I, like most everyone, fell for and believed a lot of myths, assumptions and theories proffered by supposed experts in the past and present. When many of those experts assumptions didn't work out I began learning, testing and discovering the facts. I made a lot of enemies but I also made a lot of friends but more importantly, I helped a lot of cast bullet shooters gain a better understanding of casting and shooting cast bullets.

I post the results of my tests. Some have proven my own concepts wrong yet I do post those contrary to someone's opinion. That's how I/we learn.