Pressure difference between large/small and pistol/rifle primers

[Freiheit]

I just had what I know to be a bad idea, but I'm wondering how bad.

What are the pressure differences between large pistol primers and small rifle primers?

[Griz44]

Since they don't even fit the same hole, why would it be important?

[Selena]

A: mold two light balls out of hard plastic and weigh.
B: drill out the primer hole of one (handgun) casing to accept small rifle primers
C: seat respective primer in both casings.
D: seat plastic ball
E: test fire first ball through chon & note velocity
F: test fire second ball through chron & note velocity.
G: calculate pressures for both rounds noting diff.

(Sorry, I've been around obsessed machine builders waaaaaaay too long.)

[Rollis]

One thing you can do is find some .45 cases that have the small primer hole's. Then get some with the more commen large primer hole. Make up a load. Then use a chronie, The more shot's the bigger your database will be. If you can find any rifle case's that were made using both size primer hole this will allow you to do the test with the rifle primer's. 7.62x39 is the only rifle case's that I, know for sure had this situation occur. Though there my be some .308 that had this happen in the very beginning of it's prodution life.

[Freiheit]

One thing you can do is find some .45 cases that have the small primer hole's.

Ha! I happen to have about 100 of them and no small pistol primers. I do have small rifle primers.

I'm trying to see if this is totally dangerous, or if its a matter of starting with a low start charge and working up.

[HOWARD J]

Go buy yourself a pack of small pistol primers.
Work up the loads from a good reloading manual.
Some mfrs. used small pistol & some used large pistol on their 45's.
Best to stick with what is known & not play unproven games.

[Freiheit]

I'm not planning on doing this. Even at current prices a box of small pistol primers is no big deal.

I'm still curious if there is any empirical data or load data out there on the differences in primer pressures and the effect on loads.

[HOWARD J]

Call a primer Mfr. like CCI, Winchester, Remington, etc.
Let us know what they tell you.

[RecoilRob]

The rifle primer IS a bit hotter than the same size pistol version...but not enough to cause you grief unless you are right on the red-faced maximum pressure for the cartridge. You might actually be able to measure the velocity difference between the two...but it won't be breath-taking.

I use small rifle primers in the 454 Casull as they have a stronger cup to withstand the pressures better than the pistol versions. Most load data was/is worked up with them in that cartridge.

Only really bad thing you might find with the rifle primers is a difficulty in setting them off due to the aforementioned thicker construction. My SRH will fire double action 45 Colts (pistol primers) no problem...but will sometimes fail to light the 454's. Single action no problems due to the longer/heavier hammer fall.

I have fired a fast cylinder full of 454's DA when I had the springs cranked up, but found that not really useful or pleasant! So it is now a SA only 454.