Tight Primer Pockets

Internal Volume of Brass Case

Regarding the Peterson .308 family of casings, in large-rifle-primer size, your primer pockets seem tighter than others?

On the first firing of a cartridge, whether it is ours or most others, the primer pocket diameter opens up about .0007 of an inch. SAAMI spec for large rifle primer pocket diameter is .2085 to .2100.

Our pocket diameters start out .2075 to .2078. So prior to its first firing our primer pocket diameters are slightly tighter than the bottom of spec. If we started out at the SAAMI min diameter, after your first shot you’d be in the middle of spec, or higher depending on how hot your load is.

Most of the growth in a primer pocket happens during the first firing. We size our pockets to have you at the bottom of spec after your first shot, so you can get more reloads from our casings.

Many of our customers are long-distance and competition shooters who want many, many firings from each casing.  They value our longer casing life, especially important for accuracy after the brass is fire-formed to the chamber. And of course, longer casing life translates to cost savings also.

Sometimes a customer will call in and report their primer pocket uniforming tool won’t fit when they are loading our cases for the first time. Our pocket uniformity is excellent without that, but typically after the first shot the tool will fit, if a shooter prefers to do that.

Our tight pockets present no issue for inserting primers if you are using single stage, progressive, or automated loading equipment. But they can be tight if you are using a hand priming tool. One time a shooter customer called in who was using a hand priming tool and reported that the primers he was using were difficult to seat. He also reported that he is a dentist. He said, “I don’t know if you are aware of this or not, but dentists as a group have unusually high hand strength.” I thought that was an odd thing to say, but I guess he told us that so we couldn’t come back and say he was the problem for being a weakling. Which we would never do.

We know our pockets are tight. We make them this way intentionally because our customers tell us they appreciate the longer life expectancy from Peterson casings. As always we remain eager for any input you have for us. Happy shooting.

At Peterson Cartridge our .308 family of calibers as of this writing (March 2018) consists of: .308 Win.; 6.5 Creedmoor; 6 Creedmoor; .260 Rem.; .243 Win. and 7mm-08 Rem.