Why use pistol primers in a small rifle 25-20 cartridge

Question

Loading Question >>> why use small pistol  primer in your load instead of small rifle primer. I've not loaded for this round before and am gathering info , I inherited a Savage 23 in 25/20 and want to shoot it. Been handloading 50 years and am just doing my research before buying some of your bullets. Really looking forward to playing with it. Thanks for any response ! 




Answer 

There are several good reasons on why to use a small pistol primer in place of a small rifle primer in this type of small volume low pressure small rifle cartridge.

#1 primer brisance – The lower primer brisance (amount of and duration of flame) from a small pistol primer often gives more consistent powder ignition with the small charges of powder in the appropriate powder burn rate. Ignition uniformity lends to uniformity in pressure/time and velocity and in turn lend to potentially better accuracy.

#2 Pistol primers are targeted to max pressures of apx. 40,000 psi where as rifle primers are targeted to pressures of up to 60,000 psi. For this reason rifle primers generally have thicker cup material. The thicker cup material of rifle primers will not show sighs of pressure until far beyond the safe chamber pressures of this type of old rifle cartridge. Substituting pistol primers for rifle adds a pressure indicator so adds a margin of safety to load development.

#3 Some of the vintage rifles for this type of cartridge have marginal firing pin strike energy. This condition can cause powder ignition variation an so greater extreme velocity spread from shot to shot leading to poor accuracy. I have tested firing pin energy variation and found extreme velocity variation of up to 800 fps with a pin energy low enough to cause long hang fires and total misfires. The thinner cup material of pistol primers is more compatible with the marginal firing pin energy of some of these vintage rifles. 

These are all good reasons to use pistol primers in this type of small volume low pressure rifle cartridges.