spreadsheet for calculation of chamber pressures

[KenH]

EDG - I do think we're saying the same thing, except I must not be phrasing it very clear. Nothing to do with how long the curve is, nor have sharp the spike is, what matters is the area under the curve. The shape of curve could be a sharp spike and quick drop. OR - it could be a fast rise, but slow fall of pressure to end of barrel - and as long as the area under the two curves are equal, the velocity produced by both curves should be very close to the same.

The curves are not so similar that they would make your example true.
One half the pressure will not translate into a curve that is twice as long

OK, I agree the example I used was a bit on extreme size spec'ing one as "x" and the other as "2x", perhaps I should have used "x" (20K psi) and "1.25x" (25 psi) but having the shape of curve so the area under both curves are the same. Of course the barrel id the same length, bullet weight/shape is same, everything is the same except for speed of powder to give different curve profiles, BUT - repeat again, the "area under curve" is equal for both powders.

Interesting paper, and always amazing to me how tests from 50 or 100 yrs in past can still be so valid today - that paper was 1965. In your link, table IV on page 55 it is interesting how much difference there is in the same 40 grain charge of 3031 powder - from 44.3K to 51K psi. Seems like a good size range.

Ken H>

[KenH]

OK, I found a 2008 thread over on ASSRA forum that shows what I'm trying to say. A gentlemen did actual testing of pressure using BP and a couple of smokeless powders.

In this thread: http://www.assra.com/cgi-bin/yabb/Ya...=1202959756/15 on reply #20 about midway of page. This jpg drawing shows two powders in the same 45-70 rifle, same 410 grain bullet, both are in the 1100 to 1150 fps range, with one powder giving 30K psi range while other is only 16K psi range.

Looking at the pressure graph the high pressure powder shows a short high peak rapidly tapering off, while the lower pressure powder has a pressure peak 1/2 of the sharp high pressure, but tapers off much slower.

Ken H>

[EDG]

Ken
Thanks for bringing that thread to my attention.
The curves at post #20 illustrate the high peak short duration spike vs the flatter long duration spike very well. Your eyes can fool you but it is the area under the curve that gives the velocity. The Trail Boss data shows a really sharp spike and the SR-4759 is pretty flat.

The 4759 data was good to see. I use a 500 grain bullet with a slightly heavier load so I probably get about the same velocity and a little higher pressure.

One thing to keep in mind though with the smokeless loads is they do not fill the case. Powder against the primer will give a little higher velocity and pressure than with the powder forward against the base of the bullet.

[jonp]

Excellent assra thread, ken. Thanks for digging that up.

[KenH]

Jonp: My pleasure to find the thread.

Just a question here - the 4759 power actually has a lower peak pressure than BP with a tad more velocity. Shouldn't that make it a good choice for a 45-70 Trapdoor even at 1200 to 1300 fps with a 350 to 400 gain cast bullet? I just called local gun store who has it in stock - I'm on my way to pick up a pound.

I would REALLY LOVE to find a set of graphs for many different powders showing this info.

Ken H>

[EDG]

ken
SR4759 has been discontinued but it is a premium powder for BPCR type loads. Buy all you can comfortably afford because when it is gone there will be no more.

Jonp: My pleasure to find the thread.

Just a question here - the 4759 power actually has a lower peak pressure than BP with a tad more velocity. Shouldn't that make it a good choice for a 45-70 Trapdoor even at 1200 to 1300 fps with a 350 to 400 gain cast bullet? I just called local gun store who has it in stock - I'm on my way to pick up a pound.

I would REALLY LOVE to find a set of graphs for many different powders showing this info.

Ken H>

[KenH]

I got one lb of powder yesterday, maybe I'd better go back and buy the rest they've got if SR4759 is that good. Will this powder work ok for a 30-30 lever rifle? Cost was $30 tax and all - that seems to be a decent price.

[jonp]

Yes, it's main claim to fame is that it can be reduced for powder puff loads. I found a couple of pounds and was lucky. I'd buy all that I could afford of it if I were you as EDG said. It can be used for reduced recoil loads in everything from 22-250 to 375 H&H Mag.

[EDG]

The kernels are huge and will not run through a measure well but they take up a lot of space in the case. You will probably be better off dipping and trickling loads because the grains are so coarse. The Speer manuals especially some of the older manuals have loading data for everything from the .222 up to a .458.
Yes it will work in a 30-30 with cast bullets.
I also use it in a .375 H&H with 235 grain bullets for loads that do not beat me to death.

If you cannot find data 4227 and 5744 data are very close to the same.

I got one lb of powder yesterday, maybe I'd better go back and buy the rest they've got if SR4759 is that good. Will this powder work ok for a 30-30 lever rifle? Cost was $30 tax and all - that seems to be a decent price.

[KenH]

Thanks EDG, those powders will give me a good starting place to load 4759. I went back to store today to get "all they had", which turned out to only be 2 lb. One lb was $22.97 and the other lb was $27.97 (older order vs newer order). Sure wish they'd had more of that old order

Ken

[jonp]

If you have 3lbs of 4759 consider yourself lucky. I'm hoping that the gunshow this month has some left over but I'm not holding my breath. I might buy my sweetie a Barrett 50 Cal for Christmas, though. Everytime she see's one she oo's and ah's.