Pressure formula?

[usajeep1]

O.K., here's a tricky one. I am looking for a formula to determine pressure. I know, theres a lot involved with determining pressure, like measuring cases and stuff. I want a mathmatical calculation to determine pressure. What I,m looking for would involve;
1. Powder type and specific burning rate
2. Volume of powder to be used in the charge
3. Available volume in the cartridge
4. weight of bullet
Here's what I'm trying to do. I am loading a specific charge in .45, and am messing around with bullet seating depth. I never see in any reloading data, the effect on pressure that seating depth has. I know that if you seat a bullet farther into th ecase, it will increase pressure. How much? How do you determine the increase in pressure? What if your seating the bullet farther out than some specs? Is there a drop in pressure and velocity here also? Also, can anyone lead me to a place where I can determine the burn rates of powders compared to one another? Alliant lists their powders burn rates, but only compares them to Aliiants' different powders, not any other mfg's. I have a copy of modern reloading and it lists the powders according to which one is fastest, but does not give any scale or numbers as to how they determined the information. Help please....jeep.....

[BGregory]

Lee lists powder burn rates in a chart from fastest powder to slowest. He also lists useful case volume in cc, and in the back he lists charts to find the volume in cc for a given weight of powder in grains.

In chapter 9 he lists velocity & pressure factors for 1% reduction in charges for Hogdgon and Vihtavuori powders.

I don't know of any source for the other info you are looking for.

[brickeyee]

Buy a copy of Quickload and you can investigate to your hearts content.

[Ol` Joe]

Ditto Brickeyee. Just remember that the program uses a std model for the powder burn rate and other numbers such as, jacket hardness, friction, primer pressure, ect that are likely a middle of the road figures in the allowed tolerance found in real life. this is why the manauls say to start a certain percent low and work up. The program gives good data, but work up is still needed and the pressure figure given for a load is still only a educated guess.

[usajeep1]

What page is the powder burn rate on. My book only lists the names of the various powders, note a specific burn rate for each powder. Useful case volume is easy if you know your 7th grade geometry. Volume of a cylinder=3.14*radius squared*cylinder hieght. Subtract the amount of seating depth and you have useable volume. Yes, you can compare useable volume to specific load volume to determine if your are running a compressed load. But, my question also deals with useable airspace in the cartridge, and when does the pressure rise compared to seating depth. Does pressure rise before a load is compressed. I say yes, but my quandry is by what percentage. I am working on a range comparison that involves pressures as well as velocity. I only want to work this on .45's first, and then move on. I know there is a formula out there, I'm just trying to find it....jeep...

[brickeyee]

Burn rate is dependent on pressure and temperature. It is not a constant rate as these parameters are changed by the powder burning.
The lists for burn rate are generally a comparative result based on (at best) closed bomb tests. While they provide a general guide, they are not really useful for much. The old Powley slide rule worked pretty well for IMR powders (and a few others) but Quickload has pretty accurate burning models.
As noted above, there are a number of 'canned’ values used in Quickload, but most can be manipulated if desired. For a comparative analysis they are probably not going to be very important. Case volume (cartridge length and bullet seating depth) are the two first order pressure drivers.
Air space is not really that important except for preventing a compressed load. Air (oxygen) is not required for primer or powder combustion. You could fire a gun in space just fine; with none of the annoying atmospheric drag to affect the bullets travel.

[Sudden Death]

I have purchased a book from Midway called the One Book/ One Caliber my book being The Complete Reloading Manual for the .45 A.C.P. on the back page it list 70 different powders from the fastest to the slowest I will list you a few starting with the fastest and getting slower R-1,N31, Titewad, Red Dot, Clays, Hi Skor 700-X, Bullseye, Tightgroup, American Select, Solo 1000, Green Dot, International, PB, N-320, WST, No.2, SR 7625, HP-38, 231, Unique ........ Maybe some of this will help you..

[Ol` Joe]

If you check this powder burn rate chart you`ll see the powders positions change with the listing.

http://stevespages.com/powderrates.html

Powders have NO set in stone burn rate only a general listing is possible, and the rate varies with each cartridge you use it in. If you want to play with "what ifs" and try to find loads where no data is available go with the Quick Load program as suggested above.

[Sudden Death]

Thanks Joe, I have been uondering about that stuff too I've just got into reloading last week my new Dillon arived and as a mater of fact to day I was going to go to my local gun shop and buy a few different powders to try I'am wanting to try to find a good load for my Kimber TLE ll .45 with a 5" barrel. Do you happen to know of one? Thanks once again for any and all info.

[Ol` Joe]

Thanks Joe, I have been uondering about that stuff too I've just got into reloading last week my new Dillon arived and as a mater of fact to day I was going to go to my local gun shop and buy a few different powders to try I'am wanting to try to find a good load for my Kimber TLE ll .45 with a 5" barrel. Do you happen to know of one? Thanks once again for any and all info.

Run a search hee and you`ll get lots of suggestions. You don`t say what bullet wgt you plan to use but W231 (very popular), Titegroup, Bullseye, Unique, Clays (not universal althought it works) and a bunch of others will work well with most bullet wgts. Acually any of the powders from Bullseye to Blue Dot on the burn charts will do fine in the acp with proper weight bullets. I use Titegroup or VV320 with 185gr Nosler HP and 200 LSWCs. PowerPistol get used with 230gr Gold Dot HPs in my 5" Kimber. Any of these will work with the rest of the bullets, I just prefer these combinations.

Welcome to a great new hobby!! Don`t hesitate to ask any questions that come up. The guys here will surely have a good answer or at least can guide you to one. Remember the main objective is to keep what God gave ya. Safety is #1, the fun will follow..............