We reload ammo to save money, or at least that is what we tell ourselves. It is a canard in the industry that reloading saves money, and while that is true, it becomes a hobby in itself, the crafting of fine ammunition that you just can't find anywhere else. An entire industry has built itself around reloading, with names such as RCBS, Lee, and Lyman leading the way for tools and equipment so that we can assemble ammunition.
Component manufacturers are doing okay, too. There are a lot of folks like me who choose to assemble their own ammo, and the manufacturers who make powder are few and far between. Gunpowder manufactory is a dangerous business, and making small lots of powder for reloaders is problematic. The distribution and marketing drives prices up, and when powder prices go up, so does the cost of a single reloaded cartridge. The government buys powder regularly, to manufacture ammunition for our Armed Services. They buy powder in huge lots, from the same manufacturers that sell to reloaders, but they buy such vast quantities that the price per pound is significantly lower than what I can buy it for in the retail market.
Gunpowder is made in large lots. It is tested for burn rate and pressure. Reloaders know that burn rate and pressure on a particular powder can vary by as much as 15% from lot to lot, and we adjust our practices to remain safe. Buying powder of one lot number is one of our practices. A pound of rifle powder might make 300 individual cartridges, but when that pound is gone you have to buy more powder. If that lot number is different, you have to work up your loads again to make sure that it is safe and accurate.
Neophyte reloaders are well served by retail powder. I have a fair stock of powder that I use regularly, all from established manufacturers, and all purchased over the counter from my local retailer. I continue to use standard powder, and will for the continuing future.
When you have been reloading for a number of years, you learn that there is surplus powder on the market. Powder that the government or the large outfits that manufacture for the government have purchased and is now finding its way to the market as surplus. If a single pound of powder can make 300 cartridges, then 8 pounds of powder can make 2400 cartridges. An 8 pound jug of surplus powder is all in the same lot, so it will remain the same over its useful shelf life, which stretches across decades when properly stored.
One problem with surplus powder is that it might be labeled differently than retail powder. The government wants particlar things from its gunpowder, and each type is manufactured differently, so powder that is suitable for one application might not be suitable for another. The careful reloader starts his loads in the moderate range of power and slowly works up until he finds a load that suits his needs. Most of the ammunition I load is in this moderate range. Surplus powder is a caveat emptor commodity. The buyer should beware that he is buying something that is different from other powders on the market. It was manufactured for a particular purpose.
Hodgdon makes a powder it calls H4895. IMR makes a powder that it calls IMR4895. They are similar powders but differ in burn rate. They are suitable for military rifle cartridges such as the .308 and .30-06.
Hodgdon owns IMR and one might think that the two powders carrying the same number are identical. One would be mistaken. They are different powders, differing in burn rate and pressure. Data from one can't be used safely with the other. The third powder that uses the 4895 designation is the surplus variety. It was manfactured for a particular purpose, and may or may not share the properties of either H4895 or IMR4895. The reloader is in unfamiliar territory and must use extreme caution until the powder is a known variable.
But, surplus powder is available at a considerable discount. It costs 30% to 50% less than retail powder. I just ordered an 8 lb jug of surplus 4895 and it will be delivered to my door at a considerable savings over retail. This is my first foray into the surplus powder market, and I am looking forward to the journey.