Primers expand in diameter upon firing - how much is normal?

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JimGnitecki said:
Wow, you are running a very short (1.100") COAL versus what VV recommends. And apparently successful. What prompted you to go that short?

Jim G
Click to expand...

I was getting good accuracy in my primary gun with that OAL with other powders.

One of my 9mm barrels requires the 115 HAP to be loaded less than 1.079" just to fit in the chamber!
 
I measured the primer pockets on my brand new unfired Hornady 9mm cases. It was a primitive meaurement, as I do not have pin gages, so had to use the "other end' of myu digital calipers (the jaws that open from "0" as you roll the thumbwheel). Yeah, I know this is a crappy way to measure, but it was "adequate" as a rough measure.

Out of 14 cases I measured before the fragile combination of fine motor skills and sheer boredom got to me:
4 were .1670"
3 were .1675"
2 were .1680"
5 were .1685"

Since the unfired primers are .1475", that means that there is a .0195" to .02100" CLEARANCE, and NOT an interference, between the primer OD and the primer pocket ID. So, when I seat the primer down about .006" below the case's base surface on the Dillon XL750, and they do not "fall out", since the primers are so soft I am sure they deform outward to make an interference fit with the primer pockets! How much of an interference fit? Who knows!

But since the majority of my FIRED primers are measuring as .1745" to .1775", that means they are expanding only .0000" to 030", which is not unreasonable, even if the primer pockets were NOT so much larger than the primers.

Now, IF the seating process is actually expanding the primers to fill the pockets (which seems reasonable given the pressure applied in seating them and the softness of Federal GM primers), then the actual growth from the FIRING is, at most. (.1775-.1685)=.0095" to (.1775-.1670)=.0105".

BUT a handful of them (remember the 4 out of about 50) ranged in diameter from .1800" to .1820". THOSE primers expanded a lot more. They expanded by up to (.1820-.1685)=.0135" to (1.820-.1670)=.0150". I SUSPECT (no proof) that these were the primers from the shortest COAL cartridges, back when I was getting COAL variation of up to .010". A .010" variation would indeed raise pressure since the height of the combustion chamber in my 1.142" COAL cartridges was only about 0.58" (height from interior base of case to bottom of seated bullet) to begin with.

I have no idea whether the primer OD growth is a problem or just "to be expected".

The big surprise to me is how large the primer pockets are on the brand new unfired Hornady 9mm cases. Is that normal?

Jim G
 
Walkalong said:
That's not good enough, if you are going to measure for pressure you must be able to consistently measure correctly to the nearest .0001.
Click to expand...

My measurements on the unfired and fired primers ARE consistent. As for the primer pockets, like I said, I don't have pin gages, and before I spend the money to get them, I'd like to know whether measuring primer pockets more precisely is indeed worth doing. I'm asking because the Hornady 9mm primer pockets being so large a diameter, it seems natural to think that the primers simply expand outward while being seated. Otherwise, the primers would fall out since their Pre-seating diameter of .1475" is significantly smaller than that of the primer pockets!

If the primers do get expanded during seating, the approximately .0015" variation in primer pocket diameter that I found is unlikely to have any measurable impact on the firing process.

Jim G
 
JimGnitecki said:
...... Since the unfired primers are .1475", that means that there is a .0195" to .02100" CLEARANCE, and NOT an interference, between the primer OD and the primer pocket ID. So, when I seat the primer down about .006" below the case's base surface on the Dillon XL750, and they do not "fall out", since the primers are so soft I am sure they deform outward to make an interference fit with the primer pockets! How much of an interference fit? Who knows!

But since the majority of my FIRED primers are measuring as .1745" to .1775", that means they are expanding only .0000" to 030", which is not unreasonable, even if the primer pockets were NOT so much larger than the primers.
Click to expand...
New primers expanding to fit primer pockets so they won't fall out makes no sense. You can feel the interference fit when you seat primers. I don’t know where you’re getting your primer diameters from, but they’re wrong. SAAMI SP primer diameter is .1745-.1765”. See post #9. I measured some new CCI #500 SP primers and they were .175” +/- caliper resolution.

JimGnitecki said:
The big surprise to me is how large the primer pockets are on the brand new unfired Hornady 9mm cases. Is that normal?
Click to expand...
Yes, that's normal. I just measured primer pockets of a number of mixed headstamp fired and resized 9mm cases and a .174" gauge pin was a go and .175" was a no go in all of them.
 
higgite said:
New primers expanding to fit primer pockets so they won't fall out makes no sense. You can feel the interference fit when you seat primers. I don’t know where you’re getting your primer diameters from, but they’re wrong. SAAMI SP primer diameter is .1745-.1765”. See post #9. I measured some new CCI #500 SP primers and they were .175” +/- caliper resolution.


Yes, that's normal. I just measured primer pockets of a number of mixed headstamp fired and resized 9mm cases and a .174" gauge pin was a go and .175" was a no go in all of them.
Click to expand...

You are right. I reverse two numbers when I did my calcs. I accidentally used .1475" for the primer diameter versus .1745" ! Sorry. :(

Jim G
 
JimGnitecki said:
I measured the primer pockets on my brand new unfired Hornady 9mm cases. It was a primitive meaurement, as I do not have pin gages, so had to use the "other end' of myu digital calipers (the jaws that open from "0" as you roll the thumbwheel). Yeah, I know this is a crappy way to measure, but it was "adequate" as a rough measure.
Click to expand...
Walkalong said:
That's not good enough, if you are going to measure for pressure you must be able to consistently measure correctly to the nearest .0001.
Click to expand...
JimGnitecki said:
My measurements on the unfired and fired primers ARE consistent. As for the primer pockets, like I said, I don't have pin gages, and before I spend the money to get them, I'd like to know whether measuring primer pockets more precisely is indeed worth doing.
Click to expand...
I answered that, you need to be able to measure to the nearest .0001, not rounded off .0005, and correctly every time, to check for pressure on cases.
 
OMG!

I’m retired and still don’t have the time to do more than read this thread much less perform any of the measurements nor calculations mentioned.

Right now I’m just waiting for primer to dry on the windows I reglazed last week. Then there’s yard work once neighbors are awake.
 
JimGnitecki said:
My measurements on the unfired and fired primers ARE consistent. As for the primer pockets, like I said, I don't have pin gages, and before I spend the money to get them, I'd like to know whether measuring primer pockets more precisely is indeed worth doing.
Click to expand...
Long story short, IMHO, no.

Long story long, rather than speculating and theorizing, try an experiment. Do a load workup using your favorite loading manual’s starting load and work up to a higher safe load. Then load 10 cartridges with the starting load and 10 with your higher worked up load. Fire them, decap them and measure and compare spent primer diameters. Let us know if you find a reliably repeatable difference.
 
I do not accept the concept that you can measure anything that is related to "peak pressure" in a handgun without a proper test barrel with a pizzo electric transducer or a lead crush unit. I also think that "peak pressure" means little as long it is below the maximum for the cartridge. If you really want to know find a lab and send them in for testing.
 
Gosh I'm sorry I ever raised this topic for discussion. And demi-Human, there are at LEAST 2 problems with that micrometer you referred me to at Amazon.com:

1. It costs $300 US (with shipping) = $400 Canadian
2. I would have no idea how to use a bladed micrometer properly (never before had any reason to use one)

And, note that I realized a few postings ago in this thread that I did all those calculations using an incorrect unfired primer diameter (I used .1475" versus the correct .1745"). That means that most of my fired primers had basically expanded only zero to .003", and even my worst fired primer diameter (.1820") expanded only .0075", and since heck, even the depriming process in my Dillon die could have done THATsince the depriming pin would create a LOT of radial pressure, and since I had no primer cratering or piercing or other physical symptoms, I am not going to worry about primers any more.

Jim G
 
243winxb said:
Dont be sorry. I learned about "9 Major" loads. Ty.
Click to expand...

The thing is I am NOT using a "9 Major" load. A lot of people evidently think I am simply because the Vihtavuori load table for the load shows a maximum velocity of 1401 which sounds impressively high, and a 115g bullet traveling at 1410 fps has a power factor of 161. But, 161 does NOT qualify as a 9 Major load. You need 165 to make Major I believe.

Secondly, I am NOT shooting that maximum load of 8.7 grains at 1410 fps. I am shooting 8.0 grains at about 1325 fps.

Third, Vihtavuori clearly states on its load table website that ALL the loads on the website meet SAAMI or the basically equivalent European pressure standard. So, they are NOT high pressure loads. Even the 115g at 1401 fps.

Fourthly, Vihtavouri 3N38 is a very exceptional powder. That's why I chose it. It allows pretty high 9mm velocities withOUT requiring high pressures.

Here is what Brad Miller PhD, a frequent expert handloading contributor to Shooting Times magazine says about Vihtavuori 3N38 powder:

"
3N38
3N38 is another small granule powder. It works superbly in my full-power .38 Super loads. It delivers very high velocity for IPSC/USPSA loads and lots of gas for the compensator. Vihtavuori says this powder was specially designed for competitive shooting and they recommend it for the 9mm and .40 S&W. Its burning rate is similar to Blue Dot and Vectan SP2. With some loads listed in Vihtavuori’s manual in the 9mm, 9X21, .38 Super Lapua and .40 S&W, it will exceed velocities produced by N350/3N37 by 100 fps or so. Some folks use it for 9 Major because it makes power factor at low pressure. This is high performance powder.
"

My 1325 fps load might SOUND "high pressure" to traditional 9mm handloaders, but it is NOT. It generates 450 ft lb of energy but does not require high pressure to do so because the 3N38 burns so slowly and about 30% burns beyond the muzzle. And I don't know about today's liability-conscious factory 9mm offerings because I don't buy them, but in the 1990s when I DID, 427 ft lb 9mm cartridges were common factory offerings. I remember buying and shooting many, many boxes of them. They were all of course SAAMI compliant.

Jim G
 
JimGnitecki said:
And demi-Human, there are at LEAST 2 problems with that micrometer you referred me to at Amazon.com:

1. It costs $300 US (with shipping) = $400 Canadian
2. I would have no idea how to use a bladed micrometer properly (never before had any reason to use one)
Click to expand...

First, those are not problems with the micrometer, those are your personal limitations.

Secondly, a human as experienced and detail oriented as you claim to be would have the wherewithal to spell my username correctly.

A small detail I’m sure, but coupled with quoting me differently than anyone else in both your threads, as well as responding to my simple questions and kindhearted advice with text in a shade I’m colorblind to, and referring to me as Grasshopper in the previous thread, I shall take it as the rude slight that it is.

Please continue this charade, and guessing at what you are doing. Even though there is nothing to be found regarding pistol cartridge pressure and primer measurements, you will suffer my input no longer.
 
Demi-human said:
First, those are not problems with the micrometer, those are your personal limitations.

Secondly, a human as experienced and detail oriented as you claim to be would have the wherewithal to spell my username correctly.

A small detail I’m sure, but coupled with quoting me differently than anyone else in both your threads, as well as responding to my simple questions and kindhearted advice with text in a shade I’m colorblind to, and referring to me as Grasshopper in the previous thread, I shall take it as the rude slight that it is.

Please continue this charade, and guessing at what you are doing. Even though there is nothing to be found regarding pistol cartridge pressure and primer measurements, you will suffer my input no longer.
Click to expand...

Demi-human: I apologize. I transposed the capitalization on your name. And I agree that the limitations on using your micrometer idea are my own, personal limitations. No argument there.

I had no idea you were colorblind to red. I know that a certain percentage of males are colorblind to some extent, but the color they cannot see is almost always green, not red.

The Grasshopper reference was intended to convey a need for patience with my process. I don't follow up on everything right away, as I have other things going on. I see in hindsight that you might have taken the comment as implying you are a novice. That was not my intent as you obviously are very experienced. In hindsight, I should have instead just said "Be patient with the speed of my reactions to suggested ideas".

I am seeing now that there probably is indeed "nothing to be found regarding pistol cartridge pressure and primer measurements", as the ONLY reference I have found to primer diameter growth is that one article. That's why I said, after looking hard for more info on it, that "I'm not going to worry about primers any more" as long as they aren't flattened or cratered or falling out.

Forgive my dead end research into the primer thing. In hindsight, it was a wrong turn on the path.

And please KEEP providing advice. It has been very helpful. As a retired high tech contract consultant, I know how important it is to point out to anyone who is trying to improve a process, any avenues that they might not have thought of, or non-beneficial paths they might have started down.

Jim G
 
N-105 is even slower than 3N38, and it rocks in .38 Super. I was using 3N37 with 90/95 Gr bullets in 9MM and it's still a great load, but for .38 Super and 124/125 Gr bullets N-105 does it better than 3N37 with less pressure. @fxvr5 turned me onto N-105 in .38 Super. I need to try N-105 for my light bullet 9MM load and see if I can get enough in the case.

A .38 Super case with (IIRC) 10.0 Grs of N-105 under an RMR 124 Gr Match Winner. 1345 FPS from a 5" 1911 @ 97 Degrees
RMR 124 Gr TrFP MW & N-105 Pic 1.JPG
 

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    RMR 124 Gr TrFP MW & N-105 Pic 2.JPG
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Walkalong said:
N-105 is even slower than 3N38, and it rocks in .38 Super. I was using 3N37 with 90/95 Gr bullets in 9MM and it's still a great load, but for .38 Super and 124/125 Gr bullets N-105 does it better than 3N37 with less pressure. @fxvr5 turned me onto N-105 in .38 Super. I need to try N-105 for my light bullet 9MM load and see if I can get enough in the case.

A .38 Super case with (IIRC) 10.0 Grs of N-105 under an RMR 124 Gr Match Winner. 1345 FPS from a 5" 1911 @ 97 Degrees
View attachment 987852
Click to expand...

Yes, Brad MIller mentioned the N105 powder very favourably in his article as well. You can't get enough of it into a 9mm case, but the 38 Super case is larger. I did not pay attention to his N105 comments as I have ONLY the 9mm SIG. Your 124g at 1345 fps gives you 498 ft lb of energy and a power factor of 167, which qualifies (barely) as a major load for IPSC. But that's at 97 degrees temperature. It'll be a bit less at more moderate ambient temperatures, right?

Jim G
 
JimGnitecki said:
But that's at 97 degrees temperature. It'll be a bit less at more moderate ambient temperatures, right?
Click to expand...
Should be, just depends on how temp sensitive N-105 is. We have a lot of hot days here, so I have to have loads that can handle it.
 
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