Faulty info and believes

[Chickenthief]

100+ pages back i read a thread about high pressure and speed.

There were much back padding and sayings like:
“pressure = speed and speed = pressure” and “there is no suck thing as a free lunch”

I would like to address this because I do not agree with the above statements.

Let’s take the first one “pressure = speed and speed = pressure”
Simply not so!
Load a cartridge with fast pistol powder to say 60kpsi and compare the speed to a case loaded to 60kpsi with the appropriate rifle powder.
So someone made half a statement where the rest goes something like this: “given that the powder is the same”.

And secondly I have witnessed several instances where a loading that went from @100% filling to 103-105% filling actually lost a few fps, this is due to less optimal ignition and burning of the compressed powder column.




There is indeed a thing called a free lunch in reloading, it’s called double (or triple) base powders.
If I load a case with some of Vihravuoris N1xx series to a certain pressure I will gain some % more speed at the exact same pressure using their N5xx series of powder (which contains up to 25% nitroglycerin).
Throat erosion is higher but that is another issue.






See?
I got @ 100fps for a couple of hundred psi less.

[Chickenthief]

Crappy photobucket and their downscaling.
I'll redo the calcs and crop the pics tog et higher resolusion.






I even used less doublebase powder and still got higher speed for the same pressure.

[wally bennett]

I cant recall the post you mentioned but to my eyes if you increase the charge weight you increase the pressure and the speed "WITH THE SAME BATCH OF PROPELENT".
If you use a different lot of the same powder or a different powder then you might be right because of the different burning rate of the powder whether its compressed or not. i use Viht 120 powder and in three different lots the different in charge weights to get to my desired 3.650ft/sec was 0.6grs and that my friend is a gun blowing disaster in a small 17A.H case if not lowered and worked up slowly so in my case a lowered charge weight dropped my pressure and speed witch is exactly what people are try to say.
Wally

[Dean2]

I was very possibly the one who made the statement speed = pressure. I have used it often but almost always in the context of talking about published loading data and to the effect that when you reach the published max velocity for a certain powder, bullet combination you have also likely reached the same or close to same pressure the load book developed, even if you are not at the max published charge weight. The reason for this comment is that most of the classic high pressure signs on most brass, flattened primers, sticky bolt lift, rim or case expansion and loose primer pockets do not show up till about 70,000 psi or higher, so when you see pressure effects you are already well over most high limits for cartridges. Velocity with the same bullet/powder and accounting for barrel length differences is a far better way of judging pressure if you don't have pressure gear, than reading brass and why I strongly advocate all reloaders chronograph their loads, particularly in the small cased cartridges. This clearly pre-supposes the same powder. A different powder would naturally have a different speed/pressure curve.

Even the set of variables that you advance to disprove "there is no free lunch" seems flawed. Yes the switch in powder gives you more speed at the same pressure, but the more rapid barrel wear means the gain was not actually "free".

Any saying or short cut has its limitations and there are a ton of variables that can be introduced in any conversation on reloading. I am not clear what it is you are trying to prove or disprove with this post.

[georgeld]

Don't recall the details of that thread.
BUT: I have seen many times where more powder produces less
velocity, sometimes even a loss to below what a previous charge
produced. That's what I call: "the point of no return".
Just cut it back to a reasonable level.
I went thru that stage of "faster was better and found out it's not really true'
Since then Iv'e never been a MAX loader. Just don't believe in it now.

[Bayou City Boy]

Good comments, Dean2.....

-BCB

[LT17]

Throat erosion is higher but that is another issue.

No it isn't another issue, it demonstrates that there really is no such thing as a free lunch. Whilst you may theoretically achieve higher velocities, the fact that you are paying for it with reduced barrel life perfectly illustrates the tinstafl adage.