Revolvers, Brass, and Primers

The place to discuss ammunition, reloading, ballistics, loads, and chamberings.
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JAG2955
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Revolvers, Brass, and Primers

Post by JAG2955 » Wed Oct 07, 2015 8:43 pm

So if you recall, I have that S&W 325 that just doesn't want to work right.

Today I deprimed some .460 Rowland and .45ACP that had fired. I loaded some of each with large pistol primers and some with large rifle primers.

I put on ear and eye protection and set them off in the garage. All of the large pistol ones went off just fine. Most of the large rifle ones took more than one hit. I was hoping to rule out something, other than the revolver. As I did this, I noticed that the cylinder would become hard to turn/not turn at all. The primer would back out of the pocket after firing, sometimes to the extent that it would require a plastic hammer to get it loose.

Now that I was thinking about it, that did happen the last time that I tried to shoot it, after the smith worked on it. Assuming that Newton's Laws are still in effect, I'm assuming that primers backing out without a charge or bullet is even less desirable than with a charge.

Sounds to me like it's a definite gun problem. Too much headspace? Moon clips measured out to just over .04".

Suggestions on checking headspace? And if it is a headspace problem, am I boned?

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Netpackrat
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Re: Revolvers, Brass, and Primers

Post by Netpackrat » Wed Oct 07, 2015 8:56 pm

I assume you know that large rifle and large pistol primers are different exterior dimensions, right? Large rifle primers will normally protrude from a large pistol pocket because of this. Small rifle and small pistol primers, on the other hand, have the same exterior dimensions. At least, that's how I understand it to be.
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First Shirt
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Re: Revolvers, Brass, and Primers

Post by First Shirt » Wed Oct 07, 2015 9:11 pm

According to my handy-dandy Starrett calipers, large pistol primers measure 0.121 from front to back. Large rifle primers measure 0.128. Rifle primers tend to be helluva lot harder than pistol primers, which may explain the need for multiple strikes to get ignition.

And without the back pressure of a loaded round, primers tend to back out of the pocket, which is why PawPaw drills his cases' flash holes out to about 1/8th of an inch.

Checking firing pin impact with a primed but unloaded case will only tell you if the firing pin is going far enough, and hitting hard enough. You really need loaded rounds to determine if the headspace is correct.
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JAG2955
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Re: Revolvers, Brass, and Primers

Post by JAG2955 » Wed Oct 07, 2015 9:19 pm

Netpackrat wrote:I assume you know that large rifle and large pistol primers are different exterior dimensions, right? Large rifle primers will normally protrude from a large pistol pocket because of this. Small rifle and small pistol primers, on the other hand, have the same exterior dimensions. At least, that's how I understand it to be.
My next step was going to be to cut down .308 to use with the large rifle primers. Buffalo Bore told me that they used large rifle primers in their .460 Rowland that "were within industry specifications" for hardness. I wanted to rule out a problem with the brass, which I suppose that I did. It just looks like the revolver isn't hitting the primers hard enough. I even cannibalized my Apex XP Firing Pin out of another revolver to try for this test.

First Shirt, shouldn't the additional pressure from the loaded round make the primers *more* likely to fall out?

I'm checking headspace right now via the method described at the end of this article. And since they all headspace off of the case mouth, why would they have to be loaded?

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First Shirt
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Re: Revolvers, Brass, and Primers

Post by First Shirt » Wed Oct 07, 2015 9:43 pm

Because the firing impulse involves the entire primer pocket, not just the flash hole. The initial impulse pushes the primer back out of the pocket, then the powder ignition, and increased pressure, pushes the case back onto the primer.

Does that make sense? If it does, I may have said it wrong.
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JAG2955
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Re: Revolvers, Brass, and Primers

Post by JAG2955 » Wed Oct 07, 2015 10:08 pm

First Shirt wrote:Because the firing impulse involves the entire primer pocket, not just the flash hole. The initial impulse pushes the primer back out of the pocket, then the powder ignition, and increased pressure, pushes the case back onto the primer.

Does that make sense? If it does, I may have said it wrong.
Squeezing the primer as opposed to just pushing through the flash hole?

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First Shirt
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Re: Revolvers, Brass, and Primers

Post by First Shirt » Wed Oct 07, 2015 10:40 pm

The primer flash creates back pressure, if the flash hole is the correct size. This pushes the primer back out of the pocket (part way) until the powder ignites, and the resultant pressure pushes the case back onto the primer. In normal operation, you don't notice it, it's only when you fire a primed-but-not-charged case that it becomes a problem.

That's why the CFDA cases have an oversized flash hole, because the wax bullet doesn't create enough pressure to force the case back down onto the primer. With a standard sized flash hole, the back pressure will force the primer far enough out of the pocket to cause the cylinder to bind up.

Anyone with experience using wax bullets with a primer-only charge, has seen this happen.

It's why I have a couple dozen cases, well marked, with 0.125 flash holes, in calibers .357, .41, and .45. Grandkids loves them some wax bullets!
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Captain Wheelgun
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Re: Revolvers, Brass, and Primers

Post by Captain Wheelgun » Thu Oct 08, 2015 12:31 am

First Shirt wrote:The primer flash creates back pressure, if the flash hole is the correct size. This pushes the primer back out of the pocket (part way) until the powder ignites, and the resultant pressure pushes the case back onto the primer. In normal operation, you don't notice it, it's only when you fire a primed-but-not-charged case that it becomes a problem.

That's why the CFDA cases have an oversized flash hole, because the wax bullet doesn't create enough pressure to force the case back down onto the primer. With a standard sized flash hole, the back pressure will force the primer far enough out of the pocket to cause the cylinder to bind up.

Anyone with experience using wax bullets with a primer-only charge, has seen this happen.

It's why I have a couple dozen cases, well marked, with 0.125 flash holes, in calibers .357, .41, and .45. Grandkids loves them some wax bullets!
They do the same thing on brass for subsonic rifle loads, for the same reason. I've got some 7.62x39 brass that I'm going to drill and mark for this.
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JAG2955
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Re: Revolvers, Brass, and Primers

Post by JAG2955 » Thu Oct 08, 2015 1:08 am

So while I had the 325 apart, I learned of a trick, mod, hack, whatever to strengthen the mainspring, at least, according to the internet.

Take a spent primer, and pull the anvil out. Use a punch and hammer to knock the primer dimple back out. Put it over your strain screw and tighten.

I did it already, and I'll test it tomorrow, but it does feel like the hammer is harder to pull back. Hopefully it can set off those mystical rifle primers.

My google-fu has failed me, does anyone know of an extra power mainspring?

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Re: Revolvers, Brass, and Primers

Post by toad » Thu Oct 08, 2015 3:31 am

I'm assuming you checked the "face" of the frame for any unnecessary rough spots. :?: Any chamfer burrs in rear of the cylinder :?:

Some times a little flit or bore shine polishing where the primers slide will "cure" a problem. :?

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