[provalov]

When I started reloading pistol rounds, the friend who got me started suggested that I use small rifle primers in my pistol rounds for a more sure ignition of the powder. Said that's what he and the old-timers who trained him had always used.

Well, that's what I have done in my 38Spl, 9mm and 40S&W loads. However, as I have read the various reloading boards, I've never seen any other reference to this practice. So, anybody else do this? Any reason not to? Thanks in advance for the input.

[KP95DAO]

This is what is generally done, and what I do , with loads that generate relative high pressures. This helps with primer flow. There is no benefit other than that and is harmful in that it takes a stronger blow to set them off.

These primers are also used in a couple of the normally large primer pocketed rounds such as 454 Casull and 45 Super. This because of the better pressure handling of small primer pocket cases (as compared to large pockets in the same case).

[Quantrill]

A test done a few years ago by the NRA found that the practice of using rifle primers for pistols doubled the size of the groups as well as needing a stronger hammer strike. Quantrill

[bogie]

Essentially the only difference between SR and SP primers is that the SR ones are made of a stronger metal. Which means that they need to be hit harder to go off. If you want a hotter primer, there's the SPMagnum variety. Start low, and work the load up.

[FCoelho]

Provalov - In developing loads for the .40 Super cartridge I started with a standard large pistol primer. Depending on the gun that was converted to handle the cartridge we would sometimes see primer flow. We then re-designed the case for a small primer pocket and used a small rifle primer. The problem with primer flow went away and reliable ignition was the norm. This was also the case with the 450 SMC cartridge where we used a small rifle primer versus a large pistol.

However, when it came to .38 Spl, 9mm and .40 S&W we used standard small pistol primers (Fed 100). There was never a need for anything harder or hotter.

[Bottom Gun]

I use small rifle primers to load .38 special and .357. I haven't seen any difference in performance or group size.
You can't do this with large rifle in large pistol though. There is a height difference.

[KP95DAO]

Bottom Gun,

You can if you deepen the primer pocket with Sinclair's large rifle primer pocket uniformer. Works quite well, and you can still use the pistol primers.

[Jeeper]

Most people that shoot in USPSA use small rifle in both 38 super and 40.

[trapshooter]

Vihta Vuori lists thier .357 Mag loads with a SR primer. I follow whatever recs I find in manuals in this respect, as I don't have a chrono, and can only check pressure visually on the fired case. I don't experiment with swapping components.

[Bacchus]

Some of the larger calibers require small rifle primers (such as 454). I stick with pistol primers.

[PaulS]

Using a rifle primer where a pistol primer is supposed to go is less (LESS) dangerous than using a pistol primer where a rifle primer should go.
Rifle primers have more brisence than the corresponding pistol primers which means they produce a "hotter" flash that travels further. It can raise pressures BUT a pistol primer is not made to take the 50000 psi that some loads can generate. As a result the primer will rupture causing damage to the gun or shooter or both. ALWAYS use the recommended primer for your load.

PaulS

[provalov]

Thanks to all for your replies. I've learned some interesting information from them.

Jeeper: Why do most people that shoot in USPSA use small rifle primers in both 38 super and 40S&W?

[Jeeper]

Basically for the reasons listed above. The rifle primers can take higher pressures which is good since a lot of competition loads run at very high pressures. Most competition loads are above where you would normally run. Both 38 super and 40 are high pressure rounds anyway.

The power factor for USPSA just got lowered which might change this a little but I doubt it.

[Pistolsmith]

Bottom Gun, who posted above, has it right. Therre is no difference in group size or performance in general.
What small rifle primers do in high intensity cartridges is to give more brisance, and thus more powder is being burned.
Place a large sheet of white paper about 10 fet ahead of the muzzle and fire a shot with a standard pistol primer. replace the paper and fire a shot using a small rifle primer. The latter will show less unburned powder granules, as demonstrated by less burns and scorch marks around the bulet hole.
The "larger groups" noted by the NRA were due to a psychological
reaction. Tests from a machine rest proved, in every caliber tested using small rifle primers, that the only difference was that more powder was burned. It is altogether possible that a given load in a standard loading book shows more powder than necessary. If it doesn't burn in the chamber and barrel, it is wasted. Adding more powder than necessary raises chamber pressure, not from the effect of more powder burned, but from the unburned powder taking up space in the case and the lesser available expansion space creating more pressure. Tests show that after the optimum amount of powder is introduced, restricting combustion space with a commensurate amount of Cream of Wheat, rather than additional powder, will raise presure identically. The only conclusion to be drawn is that you cannot have too much brisance, and many scientific tests by Frankford Arsenal (such as the addition of frontal ignition tubes) bear this out.
You might want to remember that unburned powder granules have a "sandblast effect" on a barrel, throat, topstrap and forcing cone. That is the downside of using a slow burning powder. Obviously, the effect causes deterioration at a very slow rate in some cases.