Shooters who load their own ammunition generally rely on published loading manuals, at least as a starting point. Many handloaders own a chronograph, to measure the velocities of handloads. Advanced handloaders also own an Oehler pressure-measuring system to get pressure data of their loads. And at least one enthusiast bought an ammunition company's entire ballistics lab when that company (Super Vel) went out of business in 1976.

Those of us who have progressed to the point of designing and making our own new calibers and/or loading bullets considerably heavier or lighter than the ones the factories offer face another issue: Where to start? In some cases, it is possible to find an existing cartridge/bullet combination that is proportional, i.e. a bigger or smaller cartridge that fires a bullet of the same sectional density with the same case capacity to bore area ratio as the new design. Then, known loads for existing calibers can be scaled up or down (starting low, of course.) Sometimes, no such proportional cartridge exists.

The Powley Computer is a marvelous slide-rule-type device invented by ballistician Homer Powley in the 1960s, which will give good starting loads when you plug in the appropriate numbers. I have used one since 1972. (I don't know if they are still sold. Anyone have a source, email me and I'll update this page.) The Powley Computer has its limitations, mainly that it lists only DuPont powders, and many cartridges fall outside its parameter ranges, such as heavy-bullet handgun ammo, and any ammo loaded to less than modern rifle pressures. There are now sites on the Web that have computer versions of the Powley Computer (they still are limited to DuPont powders.) Do a Google search.

A decade ago I came across a DOS-based computer program called Suggest-A-Load that does exactly what I want in load development. You can download it here. You specify maximum acceptable pressure in CUP (which is not exactly the same as PSI, I'll explain this in another article), case capacity in grains of water, bullet diameter, bullet weight, bullet length, barrel length, and overall loaded cartridge length. It gives you calculated powder charges (not just DuPont powders) and pressures. My tests with chronographs and pressure guns confirm that the predicted data is very close to the results experienced.

To use this program, you need a good scale (electronic is easiest), a good dial indicator caliper, and a syringe or eyedropper. Measure the case capacity full to the mouth in grains of water. Don't rely on what some printed source tells you the capacity is, measure it yourself in the cases you will be using. Double check it and get it right. Same with the case length (usually .010"-.015" shorter than listed in manuals) and overall length of your loaded ammo. Plug in these numbers, along with the maximum allowable chamber pressure of your gun (be conservative here), and Suggest-A-Load will give you the powder type, charge weight, predicted velocity, predicted pressure, and recoil energy.

I used Suggest-A-Load to get numbers for the new S&W .500 Magnum cartridge that are nearly identical to the actual experimental results seen here that Peter Pi at Cor-Bon achieved. Then I used it to determine that my long-nose bore-riding 650 grain bullet I designed for this cartridge should be able to be driven over 1250 FPS safely. When S&W sends me my gun we'll find out. 8/1/2003 UPDATE: I achieved 1265 FPS in the S&W .500 revolver with my 650 grain bullet I designed, using 10% less powder than Suggest-A-Load recommended. Pressure was 58,000 PSI in the S&W pressure gun, which is about 49,000 CUP. (S&W says 60,000 PSI is max. allowable, so this is a top load.) Suggest-A-Load said the load would generate 48,560 CUP. The 10% less powder I needed can be explained by a different burning rate production lot of the non-canister powder I was using, which is why you should always start low and use a chronograph during load development.

My only complaint with Suggest-A-Load is that the program asks for data one line item at a time and does not display previous line items until the final calculation. If you are doing "what if" exercises, such as changing only the barrel length to see what the velocities will be in guns with different length barrels, you have to start from the beginning and enter everything all over again. I would like to be able to see all lines of data and change one or all of them and hit "ENTER" again to get another calculation. If some programmer out there wants to tackle this computing problem and rewrite the program to change the layout of the data entry system, I'd appreciate it. Email me at jrinvest@earthlink.net. The original software developer no longer supports Suggest-A-Load.

I have found one small error in Suggest-A-Load that could potentially cause a problem. If you are asking it for data on a cartridge with an extremely high case capacity shooting a bullet of extremely heavy weight for its diameter, it may give you a powder slower burning than 5010, which it calls H570. H570 is an obsolete Hodgdon powder unavailable since 1979 that is a bit faster than 5010, and would cause dangerous pressures if used. What I think Suggest-A-Load meant to say instead of H570 is T570, a surplus 30mm cannon powder sold by Thunderbird Cartridge in Arizona in the early 1980s. T570 is slower than 5010. It too is obsolete and unavailable, though some people who shoot cannons still have some. The only small arms cartridges I've found for which Suggest-A-Load will recommend "H570" are an Improved .50 Browning cartridge shooting bullets of 750 grains or greater, and the 20mm Solothurn/Lahti cannon round with bullets of over 2000 grains. (T570 is the correct powder for these case/bullet combinations.) Use caution and don't follow any program blindly.

It should go without saying, but I'll say it anyway: Use this article as a starting point for your own investigation into Suggest-A-Load or any other loading aid, not as the gospel. Handloading is serious business, be cautious and proceed methodically and slowly. The author makes no claims about Suggest-A-Load, the Powley Computer, or handloading in general, other than his own personal experience in his own lab with his own guns and ammunition.

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