10mm Small Primer Pockets

[Braxton1]

We go through a good amount of 10mm at my job. I have recently become interested in 10mm as I've bought a G20 Gen4.

I remember when 10mm Auto was being developed in the 80s. One of the reported "downsides" was its use of the Large Primer. Lot of folks disliked that because on that small casehead, the Large Primer occupies a large portion of the real estate and makes it more-likely that the ejector will strike the primer while you're unloading a live chamber. This results in an out-of-battery detonation. Every reloading manual/website that I can find on the 10mm still refers to it being loaded with Large Pistol Primers.

Imagine my surprise when I found that a majority of the brass I was seeing had Small Primer pockets. I am finding no reference to that change in SAAMI paperwork. I can see why they did it (streamlining the logistics chain), but the change eliminates my option for loading 10mm on my Dillon 1050s. Trying to cram an LP into an SP pocket is a sure-fire way to have a Primer Magazine explosion. I've lit one Large Primer like that whilst loading 45 ACP, but luckily didn't light the tube....

 

[atljetmech]

45 ACP has both large and small primers too depending on manufacturer. I sort them in batches accordingly and only reload one type at a time. I have no problem accommodating either size as I'm single stage press one at a time anyway or sometimes I'll even use my hand primer tool which is also one at a time.

I'm not familiar with progressive presses or Dillon really but can you not change something out to accommodate batches with the small primer?

 

[palmettomoon]

45 ACP has both large and small primers too depending on manufacturer. I sort them in batches accordingly and only reload one type at a time. I have no problem accommodating either size as I'm single stage press one at a time anyway or sometimes I'll even use my hand primer tool which is also one at a time.

I'm not familiar with progressive presses or Dillon really but can you not change something out to accommodate batches with the small primer?

Pain in the ass to change. Most of us buy another progressive for LP or SP.

 

[1006]

I have not seen any of the Small Primer 10mm, but I like the sound of it. I prefer to be able to use Small Rifle or Small Pistol in everything.

Incidentally, I have had an out of battery detonation while clearing a jam on a10mm 1911. It surprised the heck out of me, blackened my thumb and stuck a small piece of brass into my shoulder-just far enough to draw a drop of blood, but not any deeper than a thorn caught in the leg while brushing up into briars. Anyhow, it taught me not to look into the ejection port while clearing jams-just roll the port towards the ground and rack, ect.

 

[Braxton1]

Has anyone done side-by-side chronographs of 45 ACP or 10mm to see if there's any appreciable velocity or consistency differences between the two?

If not, that'll be my project for next weekend...

Edit to Add: I sorted out all of the brass that I have. The Hornady, Double-Tap, and Starline brass is all LPP. Only the "HEVI-SHOT" headstamp is SPP.

 

[gyppo]

External detonations are a real thing. I saw a lady experience one in a match last summer. She was shooting 40 major. The bullet hit her in the lip and cut it pretty deep. There wasn’t enough of the case left to identify on sandy soil. When she lifted her lip there was so much blood I thought her tooth was gone but it turned out that it did not break any teeth. She finished the match. I was impressed.

 

[Overwatch1]

Ordered some 10mm from Federal last year and it was all SPP, first that I had seen. Been shooting 10mm since late 90’s.

 

[Cruisers460]

Interesting, I've saved a can full to reload but never bothered to check out the primer size yet. Guess I better plan on some unexpected sorting.

 

[gyppo]

45 ACP has both large and small primers too depending on manufacturer. I sort them in batches accordingly and only reload one type at a time. I have no problem accommodating either size as I'm single stage press one at a time anyway or sometimes I'll even use my hand primer tool which is also one at a time.

I'm not familiar with progressive presses or Dillon really but can you not change something out to accommodate batches with the small primer?

You can change them out. A Dillon 1050 or 1100 requires the change of a few parts that need to be tweaked to get them exactly where I want them. I load range pickup brass and there is a range of depths in the primer pockets of the brass.

 

[MILSURP Collector]

I just reloaded some FC head stamps that took small primers, shot great.