Due to the non-availability of primers at a reasonable price. I still have about 600 rounds of brass I'd like to load. I am out of the CCI 450 Magnum Small Rifle primers. But, I do have plenty of CCI 550 Magnum Small Pistol primers. I've read that these are interchangeable, but the primer base is thinner on the pistol primers than on the rifle primers.
Is there any difference? An inquiring mind would like to know.

Thanks
Chris

Apart from the primer bases being thicker or thinner I understand that rifle primers also have a bit more priming compound that their 'equivalent' pistol primer. Using small pistol primers in small rifle cases is heading in the safe direction rather than small rifle in small pistol cases in so far as priming compound, however there is still the issue of the base thickness and resistance to the firing pin blow.

If the rifle has a lighter firing pin blow and good rounded tip on the firing pin then you may get away with using small pistol primers. You could always load a 223/5.56 cartridge with the 550 primer and try it. Needs to be a fully loaded cartridge not just a primed case. Wear safety glasses and being a 223 you can hold away from the body. Some shooters experience a pierced primer on the odd occasion and it is usually not a big event with modern rifles.
I wouldn't recommend it as a good practice to use small pistol primers in place of small rifle but it may be an expedient practice under some circumstances.

Providing you are not shooting a ball powder on a really cold day, I see no problem.
If you see "cratering " back your load off one grain.

Thanks for the replies guys.
Chris