I've just run into something new to me, new Winchester 30-06 brass with really tight primer pockets.

Of the first twenty cases from a new bag, I had to double seat 6 of the cases to get the primers flush with the case and I mean really step on them!

I then took a sample of eight cases from the remainder in the bag and got these primer pocket measurements: three were .203", two were .205" and two were .207". I measured the CCI large rifle primers 200 and all were .210".

Do you think these pockets will stretch out with use or should I send them back to Winchester or the store?

Buy a Sinclair primer pocket uniformer and be happy they are a bit tight instead of a bit loose.

it could be just me, but i have noticed some differences in new brass. I just got through sizing some new winchester 270 brass and the mouths were smaller than i thought they should be for new brass, and you could feel pressure running them through the die. This is one new brass. I have heard but don't know for a fact that a lot of brass is made in serbia these days and just labeled whatever. It could be true and the tolerances aren't the same.

Try Winchester primers instead and you should be good. They tend to run a bit smaller (or is it softer?) I like CCIs (and other plated types) in older brass where pockets may not be "new" tight.





I've been running some Serbian make PRVI brass in my 7 Mauser. It's much better than the Remington stuff I previously bought in several lots. The primer pockets, however, are very tight in the Serb stuff.

I find Winchester primers un-useable due to seating so loosely in my brass, hence use CCI which are nice and tight.
Cheers...
Con

I have found that unplated (brass colored) primers are looser than plated (silver colored) ones.

I've had the same issue with some new Winchester 270 brass using WLR primers. I could barely get them to seat flush using a Lee Autoprime.

Was also wondering-Will they loosen up with use??

Or RCBS primer pocket swager. Easy to use and does a very good job. No oversize from using it.

The reason I started uniforming to begin with was because of the occasional batch of brass with tolerances on the tight end, not for the supposed accuracy increase.

You want TIGHT?
I have been running two batches, one is some brown box Federal Lake City XM stuff. Deprimed, then I reamed the crimps, and wow, those WSRs just had to be steered into the pocket. TIGHT.
Then the next project was to deprime some PMC. I thought I was gonna bust the pin (Hornady necker with RCBS rod) and had to put a backer nut on the rod, half-mooned those babies out past the crimp.
I have no idea what will happen later, I'm squashing the PMC's down for Fireball, but have a feeling it's going to call for --

A swager. RCBS makes one for your press, a PITA to use, and then Dillon has another.