Do jacketed bullets create more pressure?

[44 AMP]

That does seem to make sense.

BUT,
Now I am wondering if we are making an assumption that might not apply to other cases.

Looking at other data, other sources, different powders, I see jacketed bullets using more powder at max than lead (and in some cases more powder for starting loads than lead bullet max), and in other cases, identical amounts of powder at max for both lead and jacketed bullets.

your data supports your argument (naturally) but I am not seeing the same thing as a constant in other data. So I am thinking we are not taking something into account in our discussion.

I stand by my belief that it more difficult to drive copper through a rifled bore than lead. What additional factors are giving one result in some data and something else in other data, I do not, at this time know, but I suspect we are missing something....

[steve4102]

Originally Posted by 44 AMP

I stand by my belief that it more difficult to drive copper through a rifled bore than lead. What additional factors are giving one result in some data and something else in other data, I do not, at this time know, but I suspect we are missing something...

That's why when the OP asked " Is the pressure increase in the 300 grain because of the copper jacket?", I answered "Maybe" in posts #3,7,15,17 and 23. We as handloaders without testing equipment just do not know for sure.

You maybe correct that it is harder to drive a copper jacketed bullet through the bore, but that may not be the reason for the higher pressure.

I posted this in #13 and I believe this could explain the reduced pressure with jacketed bullets. Again just a theory.

One theory why Jacketed bullets produce less "Chamber" pressure is "obturation".
A properly sized lead bullet seals off the bore and traps the gasses behind the bullet. A harder jacketed bullet does not seal the bore as well or as completely and gasses can escape past the bullet thus reducing "Chamber" pressure.

Notice the gasses escaping prior to the bullet leaving the bore.

https://www.youtube.com/watch?v=otpF...e_gdata_player

[steve4102]

Originally Posted by Brian Pfleuger

There is NO QUESTION that, all else being equal, a jacketed bullet requires more pressure to engrave than a lead bullet. That pressure can ONLY come from the chamber pressure.

Apparently others disagree. This is from John Barsness of Handloader/Rifle Magazines.

" Normally a lead bullet of the correct diameter and hardness produces more pressure with the same powder charge, because it does seal the bore better.
_________________________
John"

[Brian Pfleuger]

I don't care how many people disagree. Consensus does not make truth, numbers who disagree does not make wrong.

Here's a thread where UncleNick say almost exactly what I've been saying:

http://thefiringline.com/forums/showthread.php?t=187292

Here's another:

http://thefiringline.com/forums/showthread.php?t=187292

Don't think Nick knows either? Google it. Almost every thread, every where, says the same thing. It is generally true that jacketed makes more pressure than lead.

The "seal" around the bullet is a minor cause of pressure variation. Neither bullet (properly sized for the barrel) "leaks" enough gases to make any meaningful difference in pressure.

I can find people who think the earth is flat. That doesn't make it true.

[steve4102]

Yes, I read those threads. I can also produce just as many if not more that say just the opposite. I can also provide enough load data to prove both scenarios correct.

...and you should care! May in fact be wrong!

[steve4102]

More data that shows Lead produces more Chamber pressure.
This is also from John Barsness.

Here's somedata from Hodgdon's website:

.44 Magnum handgun--
240 cast/ 22.0 IMR4227/ 33,300 CUP
240 jacketed/ 22.0 IMR4227/ 28,400 CUP

.38-55 rifle--
250 cast/ 27.0 H322/ 27,000 CUP
255 jacketed/ 27.0 H322/ 25,500 CUP

250 cast/ 24.0 IMR498/ 36,200 CUP
255 jacketed/ 24.0 IMR4198/ 31,400 CUP

Please not that even though the jacketed bullet in the .38-55 weighs 5 grains more, pressures are less with the same powders charges. And in all the above instances, the STARTING load with jacketed bullets is the MAX load with cast bullets.

I don't know who "Nick on another forum" is, but all he has to do is look at the vast amount of pressure-tested data available today to realize he's FOS.
_________________________
John


Link.
http://www.24hourcampfire.com/ubbthr...ressure#UNREAD

[Brian Pfleuger]

UncleNick, the moderator of THIS forum? You know him? Obviously, you aren't even examining the evidence I present as that one link leads to another thread here.
You win, lead makes more pressure. I give up.

[steve4102]

UncleNick, the moderator of THIS forum? You know him? Obviously, you aren't even examining the evidence I present as that one link leads to another thread here.

Sorry Brian, but you presented NO evidence. I presented load data and evidence as well as opinions. You on the other hand presented no data and no evidence, only opinions.

If I missed your facts and evidence, I apologize, please refresh my memory.

[steve4102]

I took some time and read through my Lyman 48 and Hornady #7, looking for any information on bullet composition and pressure. Hornady had nothing. Lyman had a small paragraph in their, "Mystery of Pressure" section page 99.

It basically said bullets are not created equal and can have a huge affect on pressure. Length, bearing surface, bullet hardness and composition can all play a role in chamber pressure. Hard (jacketed) bullets can be sensitive to bore diameter and rifling style and cause higher pressure.

It went on to say, Don't assume any rule of thumb to be true, especially this one. Sometimes a "hard" bullet shows lower pressure while the softer bullet shows higher pressure. A soft bullet may cause higher pressure because the bullet is so malleable that the sides will push hard against the bore when high pressure is exerted on the base.

It ended with this, So the rule is simply this, "assume nothing".

[44 AMP]

Lyman has been doing things with bullets for a LONG time, and that sounds like pretty sage advice.

Hadn't thought of pressure on the base forcing the sides to grip harder, taking more pressure to move through the bore, meaning higher chamber pressure, which puts more pressure on the base, forcing the sides to...

I can see a loop right there....

and I think I found ONE of the things that we were missing.....

That being, while it does take more pressure to drive a copper slug through the rifling than it does for a lead one, that pressure (for both) is well below what is generated when a round is fired. SO, while true, to the question of why the lead gets to peak pressure sooner (less powder) it is a moot point.

[steve4102]

I got this from Western Powders.

Steve,
Lead bullets are generally longer than jacketed bullets, thus using up more case capacity, which in turn increases pressure. Lead bullets usually take less powder to reach max pressure, but generate more velocity than jacketed bullets.


Don W.
CSR Western Powders
406-234-0422