Primers are an integral part of the cartridge system, just like powder, cases, and bullets.
In short, any variation in any of these can to a greater or lesser extent affect the pressures generated during firing.
Rule of thumb, is to refer to a competent reloading manual and only use magnum primers when the manual recommends it.
In general, .270 Winchester will not require the hotter ignition of a magnum primer, and use thereof could lead to problems.
BE SAFE!
D.
PS: If you would like to experiment with primers, changing primer manufacturer's within the category, such as F210M for WLR, CCI 200, BR2 or Remington 9 1/2 primers can affect accuracy in a specific weapon and are worth experimenting with. I generally only change one component at a time so that I can see the effects of that change.
Magnum primers can be used for very low temperature application, but this should be done with care.
[ 02-17-2004: Message edited by: DMCI ]