Variance in primer size

[Hypnogator]

Last night I reloaded some twice-fired LC-13 cases with CCI-41 and CCI-400 primers to test different loads. I found, to my surprise, that the CCI-41s slipped easily into the primer pocket, with almost no resistance. Now, an enlarged primer pocket is usually a sign of very high pressure, but all of this brass had been loaded with fairly mild loads. Some of the cases were so loose that I was able to deprime them by hand!

I finally found 25 cases that retained the primers adequately, then, just for gits and shiggles, I tried priming the "too loose" cases with CCI-400 primers, and they all primed with what I consider "normal" resistance. So I miked the primers, and found that the CCI-400s uniformly measured 0.175" in diameter, while the CCI-41s uniformly measured 0.174".

I don't know whether the batch of 41s that I bought are slightly out-of-spec, or whether they are manufactured smaller, perhaps to facilitate crimping.

Just wondering if anyone else has experienced this phenomenon?

 

[rcmodel]

If you can de-prime them by hand, the cases are beyond their useful life.
Get rid of them.

Normally the primer cup will expand in the cup to fill all available space and seal off the hole.

If the pocket has expanded so much they don't, or can't?

The brass is scrap metal.

rc

 

[ArchAngelCD]

I finally found 25 cases that retained the primers adequately, then, just for gits and shiggles, I tried priming the "too loose" cases with CCI-400 primers, and they all primed with what I consider "normal" resistance. So I miked the primers, and found that the CCI-400s uniformly measured 0.175" in diameter, while the CCI-41s uniformly measured 0.174".

I can not for the life of me think a difference of only one one-thousand of an inch will make a difference in the seating of a SRP in .223 brass. I could be wrong but that is such a very small number I doubt it can be felt.

 

[Blue68f100]

0.001" can make a interference fit NOT be. Just depends on what they were to start out at. Did you measure your pocket to see if it was in spec? Normally if I recall there is 0.005" - 0.001" interference between the pocket and primer. The spec is rather large ± 0.002" for the primer pocket if I recall.

 

[Reloadron]

You can look at it this way. Small rifle:

Primer Diameter is between 0.1745" to 0.1765"
Primer Pocket Case is between o.1730" to 0.1745"

Those are the SAAMI specifications. You may want to look at your case primer pocket diameters. The worst case scenario would be a primer diameter at the minimum of 0.1745" and a pocket maximum of 0.1745". On average the CCI 400, CCI 41 and CCI BR4 small rifle primers I have sitting here come in around 0.1755".

Ron

 

[spitballer]

I agree maybe it facilitates crimping. Some sealer might keep them from expelling gas before they smoosh against the pocket wall.

 

[Sunray]

The CCI-41's are just magnum primers. However, like RC says, if you can deprime by hand pitch those cases.

 

[mdi]

I'm with the guys that say toss 'em. I would sincerely doubt anyone would manufacture a case or primer that depended on a crimp or a sealer to take up the slop, difference in diameter, in the pocket diameter even it there was "tolerance stacking"...

 

[wild willy]

Years ago I got some Winchester LRP that were undersize I only bought 100.
Every other LRP I had fit fine other brands and other Winchesters.So yes it can happen.

 

[243winxb]

LC-13

Was the crimp removed by swaging the primer pockets?

 

[Hypnogator]

Was the crimp removed by swaging the primer pockets?

No crimp. They were new unprimed cases.

FWIW, the cases I reprimed with the 400s all fired normally, no sign of loose primers or gas leakage.

 

[twofifty]

pinholes and undersized WLRs

I ran into a similar problem this month, with a new lot # of Winchester WLR large rifle primers. The WLRs measured a consistent .209" ... they should have been .211".

The primer pockets (Lapua at 3rd firing) measured a consistent .209". (Measured with a caliper not a micrometer, so the results are likely +/- a thou).

Anyhow, the end result is that gases burnt a small hole through the primer radius (not the firing pin indent), allowing gases to etch a circle in the bolt face. The same under-max load with the previous lot of WLRs had worked flawlessly.

An online search revealed that Winchester was making undersize primers for awhile in 2013. I have yet to hear back from Winchester on this.

I have re-worked this load with CCIs (dia. of .211") in the same Lapua brass and have had no problems whatsoever.

 

[mdi]

First post talks about twice fired brass? So, are they new or twice fired?

 

[Hypnogator]

New brass, loaded, fired & reloaded then fired again. Was reloading them for the second time.

Again, loaded fine with CCI-400s, fired without incident. No signs of gas leakage around the primers.