small pistol versus small rifle primers

[rumblebee1967]

Working up a load for 9mm USPSA major in 9mm and chronographed the same load using small pistol primers and small rifle primers. The small rifle primers consistently chrono at lower velocities than the small pistol. Using winchester Autocomp powder in a compressed load. I thought this was the opposite of what I would have expected in the velocities. Looking for similar experiences and/or an explanation of why.

 

[ArchAngelCD]

I can't give you are reason why SRP deliver less velocity than SPP but I will tell you the SRP have a thicker cup than the SPP and might not ignite as reliably as a pistol primer when struck with a lighter blow from a handgun over a rifle firing pin. Since you said this is a USPSA load I would shy away from anything that might not be reliable, especially in competition.

 

[rightside]

What is the difference in velocities you are seeing?

I use either SRP or SPP and have never had an ignition problem with the SRP out of my 9mm 1911.

 

[GP100man]

2 things can happen ,the srp is pushing the bullet out & giving a bigger "combustion chamber" or a lite strike affecting the primer burn.

 

[rcmodel]

This!! (post #4)

I'd guess the bigger pop is moving the bullet in the case before full powder ignition & full pressure takes place.

rc

 

[243winxb]

"Too Much Primer" as in Post 4. http://www.shootingtimes.com/2011/01/04/ammunition_st_mamotaip_200909/

 

[USSR]

"Too Much Primer" as in Post 4.

Not necessarily. Without knowing the degree of velocity difference, it's hard to make a call. Standard SRP's are less powerful than Magnum SPP's, so it could be just a difference between one make of primer and another.

Don

 

[DCT]

Might be thinking of another organization, but don't you have to use at least a 40 cal to make major in USPSA?

 

[rumblebee1967]

These are the actual recorded velocities, not huge differences, just surprising to find the rifle consistantly lower.

pistol primer rifle primer

1346 1336
1350 1315
1341 1329
error 1329
error 1348
1350 1348
1341 1315

1345.67 1331.40 this last line is the average for each string.

 

[rumblebee1967]

I believe a power factor of 165 will get you into major division.

 

[Jesse Heywood]

What primers? Different brands have different materials. They don't all go boom at the same time or with the same flash.

 

[rumblebee1967]

in both cases the primers are the same brand CCI

 

[USSR]

With only about a 1% difference and the same make of primers, nothing unusual here. You are likely to find that much variance from one lot of primers to the next of the exact same make and type primers.

Don

 

[rumblebee1967]

The part that surprised me is the consistency of the rifle primers being lower velocity than the pistol primers. I understand the difference is small and the variations in lots etc. none of that explains the consistency of the difference to me.

 

[ArchAngelCD]

Why is it in some threads everyone screams you should only use components that are listed in the published load data and then threads like this come along and no one mentions published load data and even tells the OP it's just fine to use a rifle primer in a handgun cartridge?

Note, I'm not one of those who thinks only strict load data should be followed but it just strikes me as strange as to the difference in some threads.

 

[Jim Watson]

9mm Major for USPSA Open is usually a maximum, often an overload.
Use of small rifle primers to disguise the signs of high pressure has been common for a long time. The guns are stoutly built and hold up pretty well.

This is fairly advanced hand loading, beyond the limits of manual recommendations or the Internet Recipe Hunt. Care and some assumption of risk is required.

I loaded a good deal of regular 9mm P with rifle primers in the 2009-2010 Panic with 100% ignition and no "pressure signs." Well, the primers wouldn't show pressure signs anyhow. But I was once alarmed by the appearance of primers in standard loads. That was when I used Federal primers out of my revolver supply instead of the usual WW or CCI.

Federal makes magnum primers now, but before they did, they recommended their small rifle primers for .357 Magnum.

Y'all be careful, now, you hear?