How to tell differences in primers

[Huskerguy]

I load mostly small pistol and small rifle. So to make this easier I have two autoprimers, one for small pistol primers and one for small rifle so I don't have to keep taking them out when I change between rifle and pistol.

Anyway, I wondered how I could tell the difference between a small pistol and a small rifle if someone mixed them up. This hasn't happened and my lovely wife would never play such a dirty trick on me no matter how much time I spend at the bench I mic a few and found some minor differences but thought that may just be a tolerance.

Just curious

 

[okiefarmer]

I think if you do a search, there has been a number of threads on the SP/SR primer debacle. Personally, I have loaded a buttload of pistol rounds with small rifle primers, they shoot just fine. Only thing I have ever heard that would cause me to not load a small pistol into a rifle case is that the primer cup material is softer in pistol primers, thus a slam fire might be possible with a heavier floating firing pin. Dunno, never had it happen, just heard that rumor. I have also heard the rumor that Obama is not a natural born U.S. citizen, but he still has the job as Prez, thus, so much for rumors.

 

[darkgael]

I believe that the difference, as in large primers, is that they are different heights. Rifle primers are "taller". The difference is about 0.003".

 

[NWPilgrim]

There is NO difference in exterior dimensions between small pistol and small rifle. Only in the large size does the rifle primers have more heighth than the pistol primer.

The SR primers have a thicker cup so a weak handgun spring might not be enough to set it off, but I have not heard of this being much of an issue. In the case of CCI SR and SP, there is no difference of any sort and they are basically interchangeable (though I would not do so just to not get into a habit that would not apply to other brands).

I have heard that manufacturers color code the inside of their primers to be able to distinguish them. I have not paid attention to my own primers so I can't vouch for this, but you could compare yours to see if the insides are blue, red, yellow, green, etc.