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

[waksupi]

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.

Pretty hard to beat empirical data. Thanks for making it available.

[Messy bear]

I am not making any predictions. Western has some pressure barrels set up to mimic the free bore in a revolver (throat and gap and forcing cone). In straight wall cartridges, they have found that peak pressure mostly occurs before the bullet leaves the case.
And sometimes before much bullet movement.
In that senerio, it seems that a bullet that seals the case and NOT the barrel is going to develop more pressure. It will be interesting...

[303Guy]

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?

Knocking or pushing out a lead boolit has the problem of expanding the boolit at its base as force is applied to it whereas a jacketed bullet does not do this. On the other hand, if the pressure of firing is high enough, the same could apply, except that the barrel gets expanded behind and partially up the length of the bullet/boolit by the gas pressure behind it. Hence the ability to measure pressure within the bore using strain gauges. This might explain the seemingly contradictory reports.

[swheeler]

Some day we will have the answer, guess it's just a waiting game now. Carry on

[DonH]

I did not read all posts in this thread but... Googled coefficient of friction and saw several tables showing coefficient of friction of various metals on other metals. The Western guy is correct: copper on steel is .23, lead on steel is .54. But then another site (engineering IIRC) showed LUBRICATED lead on steel... .14!!!
The guy should have done more research. We didn't know the numbers maybe but a fool knows lubrication changes things.

[303Guy]

There are many variable to take into account. I once fired some 218 Bee bullets in my hornet - .224 bullets in .223 groove bore with light charges. These shot erratically with some actually stopping in the bore. After a short while some of those would just drop out. They showed heat scorching. The jackets were expanding from heat, seizing the bullets in the bore. One of them was fired into a non-cotton fabric rag and actually melted the fabric to itself. There was no sign of pressure which would make sense since the bullets would enter the bore normally then heat up and stop without enough pressure to overcome the increased friction.

These bullets were also inaccurate with both light charges and full power loads, possibly due to the expanding jackets leaving the core loose within. Other .224 bullets shot just fine in this rifle.

Cast boolits could be exhibiting the same sort of behaviour. I would guess that harder alloys would show lower pressures than softer alloys under some conditions.

[DonH]

A simple test: .223 case, 55gr lead and jacket bullets, a fast powder and one rifle. Which bullet, lubed lead or jacketed will require the lowest minimum charge (think cat sneeze) to be expelled from the bore?

What is in play in (and maybe missing from) this discussion is that when a powder charge ignites behind a cast bullet launching it into a CONDITIONED bore the bullet obturates not against barrel steel but against the film of lube in the bore. Thuse the importance of the type of lube used. At low pressure anything that "greases" a bullet may suffice but the higher the pressure the more important the "film strength" becomes. Anhydrous lanolin is used in some lives but is also used in industrial drawing operations. It has great film strength. It is in my BPCR/Schuetzrn lube.
I have read and heard serious rimfire shooters talk of the importance of bore conditioning as in fouling shots after scrubbing a bore clean. Ruminating on this lead to my practice in my smokeless powder lead bullet rifles of not cleaning the bore down to bare steel, leaving some amount of lube film in the bore. My reasoning is that lube on a bullet lubes the bullet from it's grooves back and lubes the bore for the NEXT bullet fired. Given a good lube, the only bullet at risk of obturating against steel is the first shot from a thoroughly clean bore.

[Gohon]

My reasoning is that lube on a bullet lubes the bullet from it's grooves back and lubes the bore for the NEXT bullet fired.

Glen Fryxell gives a long explanation on what bullet lube really does. http://www.lasc.us/FryxellLubeCastBullets.htm One of the things he says is " In summary, bullet lube is pumped from the lube groove to the barrel surface by compression, linear acceleration and radial acceleration. In addition, lube is injected forward during the firing process, as the result of high-pressure gas leakage into the lube groove. This injection process forms a floating fluid gasket around the bullet, and serves to limit gas cutting and is a kind of ballistic stop-leak.".

Basically what he is saying is lube is formed around the entire length of the bullet...not just from the lube grooves rearward. Seems to make sense, otherwise the forward driving band would be smearing lead.

[KenH]

.....(snip)........ 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........ (snip).... 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.....

Larry, I couldn't have written a better explanation of my thinking - While I love to be right, I'm much more interested in the "correct" answer.

I'm looking forward to the results of your test.
Ken H>

[DougGuy]

I would venture to say it's like comparing apples to apples and oranges to oranges. All things being equal, the cast boolit would have less friction in the barrel, which would obviously lessen pressure in comparison to the J word.

HOWEVER.. If that cast boolit is hardcast, BHN22 and it uses that hard crayon lube, I could see where this boolit would present more resistance against swaging into the rifling, and more resistance against travel in the bore because the lube was hard and not really doing it's job, and so this boolit could raise pressures in comparison to a softer boolit with soft lube. I would figure a J word in the same weight range would fall somewhere between the two.

As far as which bullet/boolit raises pressures in comparison to the other one, the answer could go both ways depending on the boolit you use to compare.

[DonH]

Glen Fryxell gives a long explanation on what bullet lube really does. http://www.lasc.us/FryxellLubeCastBullets.htm One of the things he says is " In summary, bullet lube is pumped from the lube groove to the barrel surface by compression, linear acceleration and radial acceleration. In addition, lube is injected forward during the firing process, as the result of high-pressure gas leakage into the lube groove. This injection process forms a floating fluid gasket around the bullet, and serves to limit gas cutting and is a kind of ballistic stop-leak.".

Basically what he is saying is lube is formed around the entire length of the bullet...not just from the lube grooves rearward. Seems to make sense, otherwise the forward driving band would be smearing lead.

I do not dispute Fryxell but I am not sure how his theory can be proven. I do know that unless the bore is cleaned with harsh degreasers between shots each bullet fired conditions the bore for the next one. I could be wrong as to the reason but my practice works.��

[303Guy]

I would venture to say it's like comparing apples to apples and oranges to oranges. All things being equal, the cast boolit would have less friction in the barrel, which would obviously lessen pressure in comparison to the J word.

HOWEVER.. If that cast boolit is hardcast, BHN22 and it uses that hard crayon lube, I could see where this boolit would present more resistance against swaging into the rifling, and more resistance against travel in the bore because the lube was hard and not really doing it's job, and so this boolit could raise pressures in comparison to a softer boolit with soft lube. I would figure a J word in the same weight range would fall somewhere between the two.

As far as which bullet/boolit raises pressures in comparison to the other one, the answer could go both ways depending on the boolit you use to compare.

I lean the other way. I suggest that the harder alloy boolit will give less resistance in the bore. More initial resistance in the throat but less in the bore. That being due to having more strength to resist upset and exert pressure against the bore. So it would depend on each circumstance.

[OS OK]

Let me state a few things that I am assuming....

*The easier it is to push a projectile down the bore...the less pressure in ft/lbs of energy is required to move it along inch for inch.

*The projectile that moves easiest...travels farthest in the barrel within any given time and creates the most volumetric space behind it at a lower pressure.

*The more volumetric space there is, the less the pressure can build to a maximum before the projectile leaves the barrel and uncorks the pressure vessel...the increasing pressure is expanding into an ever increasing space...all this in such a little time frame that it boggles my mind, too many thoughts going in too many directions and I end up fogged.

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I read this years ago in an article in Speer and have tried to reflect on the events here but this is about pressures in a rifle and prolly a proof round to boot.
Anyway, I thought it worth mentioning as the first few milliseconds are prolly relative though the powders have a wide difference in burn rate.

This following 'interpretation' is from an article published in "SPEER, Manual #7 for Reloading Ammunition", pub. 1966-7. author; DR. Edgar L. Eichhorn

I had to read it several times endeavoring to understand exactly what happens in this 'Internal Ballistics' subject as it was different than I'd imagined. Another problem for me was this event all took place in 1.35 milliseconds, .00135 second, 135/100,000's second.




The 'Pyrostatic Epoch' begins with 'primer ignition'
elapsed time (et.) 5/100,000's second
the boolit is just this instant going to 'START' to move, but it has not
6,000 lbs./sq.in. pressure develops, the brass swells in chamber and seals it
4,000º F. temperature/in chamber
3 1/2% of powder charge is consumed

The tip of the boolit has traveled 1 inch, is now fully in lands/grooves and engraved, acceleration has begun
et. 40/100,000's second
70,000 lbs./sq.in. and pressure is now at maximum
3,470º F. temperature in barrel
38% of powder charge is consumed
1,000 FPS Velocity and climbing
681.8 MPH and heading toward the sound barrior [ V x FPS x .6818 = MPH ] {this my extrapolation, hope it is correct.)

The boolit has traveled 9 inches and the 'Propulsive Epoch' has ended
et. 75/100,000's second
24,000 lbs./sq. in. pressure and is in 'decline' as the accelerating boolit is making more volume behind it than the 'hi-pressure gasses' are able to fill.
2,300º F. also in decline
100% of charge is consumed
2,200 FPS Velocity and climbing as it is under 'Hot expanded gas propulsion' only, from here on out
1,499 MPH has broken the sound barrier and continues to climb

The boolit is exiting the 27 in. barrel
et. 135/100,000's second…1.35 millisecond… .00135s
6,000 lbs./sq. in. remaining pressure flashes into atmosphere and is luminous to the eye…
1,490º F. gasses and powder and lube smoke fill the air...
2,700 FPS Velocity and this now is in decline
1,840 MPH and when it travels downrange aprox. 900 yards, it will again cross back through the sound barrier where its RPM will be a critical factor in flight.
162,000 RPM as it emerges from this 1:12 twist barrel [ ((12/T) x V)60)=RPM ]…short version > [ (V x 720)/T = RPM ]…T=twist, V=velocity

"So how does this have anything to do with pressure differences questioned in this post? I haven't a clue, just thought I'd throw it in the mix and give Ya's something more to chew on."

[swheeler]

http://castboolits.gunloads.com/show...e-weight/page9

I have found dozens, if not hundreds, of examples of empirical data like this shot in real ballistics labs. You will notice that both are loaded to same OAL(HOW WE WOULD USE THIS DATA IN REAL LIFE), max charge for 230 FMJ 5.6grs and 19.7k psi, 230 Lead RN max charge 4.9 grs and 20.1k psi. Wow .7 grs more powder is a LOT in the 45 ACP case. If one used the starting load for FMJ to load that lead bullet you are close to +P pmax

[JBinMN]

Something to always remember is the length of the projectile itself & how deep into the case the Lead boolit is, vs the Jacketed bullet.

If the Jacketed bullet is .3" long & the Lead one is .4" long but the OAL is 1.20" for both, the Lead boolit when seated to that 1.20" OAL will be taking up more space(volume) inside the case than the Jacketed one, since the Lead one is longer than the Jacketed projectile even though both are the same weight. The remaining length of the round from the base of the projectile to the head of the case ( In this hypothetical .8" for the Lead while .9" for the jacketed) and thus, the volume inside for the Lead boolit would be smaller & thus allow for more pressure than the jacketed bullet would have. That would also be the reason for the difference in the powder amounts used. Less powder is needed for the Lead boolit since the powder & the resulting hot gases have less space to expand, the pressure will build faster than with the Jacketed bullet that has more space(volume) in the same size case.

The reduction in powder amount is to keep the pressure in a "safe zone" for each type of projectile in the same case, to prevent over pressures, so of course they can be different even though the rest of the data/components appear the same. ( case type/mnfr, OAL, projectile weight, etc.).

So, just using the comparison of the two, without taking into account that the remaining volume in a case is not going to be an accurate comparison. The remaining volume in the case when the two are seated is not supplied & is likely the reason for the difference in pressures between the two projectiles.

[swheeler]

You don't know how much bullet is in the case because they don't publish the "lead' bullet used, it and the FMJ could very well have the exact same seating depth, actually the lead bullet could likely have less inside the case! I wonder if Johan loubster is still at Accurate

[OS OK]

That is just 'starting pressure' from only a %'age of the powder being ignited, when the projectile starts to move that volume behind the projectile increases and that changes the volume and pressure increase until all the powder is consumed and pressure reaches maximum.

[shdwlkr]

maybe this question has already been answered and I just missed it.
Is there any difference in resistant of a lubed vs jacketed bullet? what if the lead bullet is powder coated?
I understand a lot of physics, just have not solved the resistant question

[JBinMN]

You don't know how much bullet is in the case because they don't publish the "lead' bullet used, it and the FMJ could very well have the exact same seating depth, actually the lead bullet could likely have less inside the case! I wonder if Johan loubster is still at Accurate

Yes, they "could be" the same length, or likewise, they "could be" not the same length.

Let us consider the odds a little bit.

What is the likelihood that the length of the Lead ones are the same as the Jacketed ones, Verses the likelihood that they are the same length for all the different combinations of Lead boolits & Jacketed bullets?

My bet would be that there are more differences between lengths than ones that are the same in length.

I am not trying to argue, BTW, just pointing out something that some that read here may not have taken into consideration. ( I don't remember exactly but someone mentioned this same thing some time back. I think it was Mr. Gibson, but it may have been someone else.)

Anyway, in that other related forum topic I mentioned in a post a short time back, it seems that some folks are OK with using data that is for Jacketed bullets in place of data for Lead boolits. The consideration of just where in the case the base of the same weight projectile is "highly important" for safety reasons, and thus it IMO, it has a lot of bearing on this discussion as well. If the volume remaining in the case when the projectile is seated is different than one another, then the results of any experiments will not be accurate as a comparison.

So, I was trying to point that out in the last post, that while the OAL is the same & the projectile weight is the same, the volume in the cases being compared may not be the same, so the powder amounts & pressures will not be the same.

"All things are Not Equal" for good comparisons so far & isolation of all the factors we are talking about, except Lead vs Jacketed. would need to be tested to find out, so until someone testes with all things the same, but for the difference of Lead vs Jacketed projectiles, we will not have the correct answer, but only supposition about what the correct answer might be.

We need to have projectiles that are the same in caliber, weight, powder amount, primer, case, etc., and the OAL should not be as important as having the base of each type of projectile be seated to leave the volume in the case the same. Remove all differences in variables that have an effect on the projectiles travel thru barrels of the same length with the exception in type of materials used to make the projectiles.

Until then, or until someone can show us all where such testing has been done, I don't think there is anything else, but hypothesis being presented with no proof to prove anything for a definite answer.

[Jeffjmr]

I don't really have a dog in this fight, but I will share my thoughts. Personally, ALL ELSE BEING EQUAL (which it only is sometimes) I freely use target load jacketed data for starting points for lead loads after running it through Quickload.

I think part of the problem is getting married to the theory that if velocity goes up, pressure must have gone up. You can test this theory easily if you have a HP-optional mold. Cast one boolit with the HP, the other without. The one without the HP will be heavier. Load them identically. Shoot over a chrony. The lighter bullet, same load, same OAL, same driving bands same lube will be faster. Do you really think the bullet that got out of the case easier and required less force to accelerate down the barrel produced higher max pressure?

There are simply too many variables to make a rule that lead makes more pressure than jacketed. Powder burning rate, primer, bullet depth, leade, crimp, lead hardness, ad infinitum.

Another source of data that may lead some to believe lead makes more pressure as a rule, is the loading manuals for lead that list considerably lower max powder loads for the same weight lead versus jacketed bullets. But if you read the fine print, and also apply some logic, most recipes limit lead velocities to 2200fps or less. THAT is often why the max loads are so much lower than the jacketed. Pressures are not always listed for the lead loads but when they are be careful not to mix CUP and PSI. They only rarely coincide.

Lastly, bullet ogive shapes and bullet length sometimes limit OAL, and it is possible a lead bullet will need to be seated deeper than a jacketed bullet for chambering as well as magazine fitment. This could result in a higher peak pressure depending on the powder being used.

I use Quickload religiously. Often the velocities predicted by QL are phenomenally accurate. If someone uses QL and also has pressure test barrels, I would be very interested in knowing if QL's pressure estimates are as accurate. QL graphs bullet travel vs. time vs. pressure at millisecond granularity. It is very educational. I shoot mostly milsurp, so I keep predicted and/or known pressures well on the safe side.

My $.02, free for Prime day today.

Jeff