Why do pellet weights vary?
by B.B. Pelletier
I'm writing this post for myself, as well as for the customer reps at Pyramyd Air. The situation is this...Pyramyd may list a certain pellet with a weight of 7.5 grains; but, when the customer receives his, they weigh 7.3 grains. Or. I may write a post in which I use a certain pellet that I say weighs 6.9 grains, but Pyramyd is listing it at 7.0 grains. Readers see these disconnects and wonder if anything they read is correct. Why should the weight of lead pellets vary?
Not talking about tolerances
Everyone knows that there will be small weight variations from pellet to pellet in the same tin. That is not the issue I'm addressing. I am talking about when the average weight of a certain pellet does not agree with the listed weight on the site or with the weight I have written in a posting. Why should pellet weights - the weight the company publishes - vary?
The business of making pellets
Pellets are made on automated machinery that runs constantly and turns out thousands of pellets each hour. In the larger companies (e.g., Gamo, H&H and Crosman), there are batteries of these machines turning out several million pellets every day. If you look at the types of pellets a company makes, and that includes different calibers within the same type, you'll soon see the number is very large. No company can afford to run machines to make every type and caliber of pellet they produce all the time, so these machines are scheduled to make different pellets to keep up with the demand.
The pellet-making machines are fed lead slugs that weigh a little more than the final pellet. These slugs are usually cut from lead wire that is wound on large spools and fed into a cutting machine (large companies have many machines).
Pellets are formed by precision dies
A multi-piece steel die forms the lead slug into the pellet by either mechanical or hydraulic force. The pellet-making machine operates this die set, forming the pellet and removing the excess lead, called a sprue, after the pellet is made. In a large company, there are dozens or even hundreds of dies, all are either working in pellet-making machines or in storage awaiting their turn in the machine.
Let's say a pellet company sells 50 million of pellet "B" every three weeks. It takes them four days to make that number; so, when they reach 50 million, they stop making pellet "B" and switch over to pellet "C." In another couple of weeks, it's time to start up the pellet "B" line again, so the dies are installed in all the machines. They're run and adjusted until the weights are as close to the nominal weight as they can get them. Because these machines are adjusted with each new run, they are not able to make the exact pellet weight of the new pellet until they have been adjusted and run for some time. Every time they get a new shipment of lead wire, they have to check the output of the machines to ensure they still make pellets of the same weight. If the metal supplier sent wire with a slightly different lead alloy, it will produce pellets of a different weight. Sometimes, that can be controlled...and sometimes, it can't.
Naturally, the company tries to smooth out the production cycle as much as they can, so there won't be any variation whatsoever, but you have to realize that it's also nearly impossible to control. Whenever anything changes - new pellet-forming dies, a new pellet-making machine, a fresh lot of lead wire, major maintenance to a pellet machine or anything else, the weight of the pellet can change.
There's a good analogy in reloading
Reloaders know that a turret-type reloading press with multiple functions will deliver good results, but not so good that there are no variances every time the press is run. The ammunition they make is often as good as factory ammo, but it's hard to make it any better with a fully automated reloading station. That's why benchrest shooters load at a single-station press and hand-weigh every powder charge and every bullet they load. They are like the JSB factory or the H&N factory making match-grade pellets.
If you have a real need for uniform pellets, do what the 10-meter shooters do. Buy your pellets 30,000 at a time and get all the same lot number. But, if all you want to do is have some fun shooting, you need to know that pellet weights are sometimes going to vary from the published numbers.