Primers Foreign vs Domestic interchangeable?

[87th PVI]

Another thread went somewhat off topic & the following came up in regard to shot shell primers:

Q: What is wrong with Rios? I'm new to reloading so I've never used their primers but I have used their factory ammo without any problem.

A (from member #1): The same thing that is probably wrong with Fiocchi. They are metric and are a little bit bigger in diameter than American primers. I have a MEC 9000 and other guys at the club have told me that MEC loaders will not seat them properly and they stretch the primer pocket so that American primers fall out.

A (from member #2): I had heard the same thing about Fiocchi primers (That they were just a tiny bit oversized and they would then make the primer hole bigger as to not accept other primers) So I have kept the hulls that I have used Fiocchi primers in and that is all I use those for. Problem solved.

"guys at the club told me" & "I've heard" were not exactly the sources I was looking for so...
My dad is a machinist so I had him break out the micrometer.

Key:
bottom = diameter measurement at the base just above the rim of the primer
top = diameter measurement at the firing end of the primer
ID = inside diameter of the primer hole in the hull.
All measurements are in thousands of an inch
All measurement were taken at several places around the radius so in some cases there is a range indicating that the primer or hole was not perfectly circular.

Rem 209 unfired primers:
measured five primers, of those:
four were 243 and one ranged between 242 - 244 bottom measurement.
Two were 238 & three were 240 top measurement.

Fiocchi unfired:
measured five, of those:
four were 244 one was 243 bottom
three were 243 two were 244 top


One example each of fired primers removed from the following hulls & the ID of the primer holes:

Winchester AA Hull (reloaded) with Rem 209 primer:
primer 244 bottom, 240 top
hull ID 242

Federal Top Gun hull w/ factory loaded primer
primer 238-240 bottom, 238-241 top
hull ID 237-242

RIO Star Team Professional hull w/ factory loaded primer
primer 246 bottom, 243-245 top
hull ID 244-245

Fiocchi Crusher hull w/ factory loaded primer
primer 244 bottom, 239-242 top
hull ID 241-245

Remington Gun Club hull w/ factory loaded primer
primer 240 bottom, 238-241 top
hull ID 236-241

[JohnUSCG]

Wholly Crap. You are a very thorough guy!

Outstanding info!! Thanks, 87thPVI....that info is outstanding!!

[Flash]

Thanks, 87. I am enlightened. I had no idea there was that much difference.

Flash

[Iron Sights]

Nice job 87thPVI