By John Kleespies
I’m currently researching a new .308win load for a rifle that I’m building, and in the process I discovered that there are actually two .308win brass choices offered by Lapua: “.308win” and “.308win Palma.”
When I asked Lapua what the difference between them was, they informed me that the brass is identical, except that the Palma version uses a small rifle primer rather than the standard large rifle primer.
This explanation also came with an unprompted warning: that, if I planned to use Palma brass for hunting in extreme cold weather, small rifle primers might be more prone to hang fires than large rifle primers, though the use of small magnum rifle primers might mitigate this.
I found this warning interesting and did an Internet search, and the consensus of the chat forums could be summarized as: “Small primers should be avoided for cold weather use because they are less reliable than large primers.”
That said, there are millions of soldiers out there relying on small primers to make their infantry rifles go bang in the wintertime, so this was not jiving in my brain.
Me being me, then, I reached out to an extremely well-respected primer manufacturer for an answer, and I now have an “official source who wishes to remain anonymous” that confirmed via in-house testing that small rifle primer ignition is just as reliable as large rifle primer ignition, regardless of temperature.
First off, it must be pointed out that both large and small primers use the exact same chemicals, just in varying amounts… and the same compounds will react in the same way in the same temperatures, regardless of the amount of the compound being used. In other words, if two differently-sized primers are struck by the same sized firing pin, with the same amount of force, and in the same temperature… then the chemical is either gonna go bang, or it’s not gonna go bang, no matter if there’s a little of it or a lot.
Per this company’s internal testing, failure to ignite and/or hang fires in cold weather are related to the powder, rather than the primer. Therefore, when this manufacturer assembles their own boxed ammunition for sale, they specifically choose powders that are less temperature sensitive, and their ammunition performs consistently at low temperatures.
I wrote a previous article on temperature sensitivity with gun powder, so this explanation makes sense to me. In fact, hunters who live in areas with extreme temperature variances—Alaska, and the like—will often have a “summer load” that uses one powder and a “winter load” that uses a different powder… because the summer load won’t go bang in the wintertime.
And…
Remember that Lapua’s warning was about “hang fires,” which again sounds more powder-related related than primer-related.
I suspect that we are arguing semantics here, and it’s unjustly giving primers a bad reputation.
It may be that large primers are putting out more power than small primers, and so the large primers are thus helping stubborn powder to ignite more readily than small primers; this is backed up by Lapua’s suggestion that magnum primers may be a better choice for cold weather— because they put out more power than standard primers.
This situation has created the perception that small primers are less reliable in cold weather, but that is merely a perception. The real issue is still powder related. The hand loader, rather than relying on the large primer to Band-Aid his powder problem, should instead change to a powder that is better suited to a cold environment.
I believe that it is incorrect to say that, “Small primers should be avoided for cold weather use because they are less reliable than large primers.” However, if I reword the statement to, “Large or magnum primers more reliably ignite temperature-sensitive powder in cold weather, versus small primers,” then I may have an appropriate warning.
So, if you feel better using a large primer for insurance against temperature-sensitive powder, then go for it – but properly lay your concerns on the powder, and not the primer!
As I mentioned in another article that I wrote on small versus large primer power consistency, I’ll add the disclaimer that my information is coming from a single “inside source” and probably should not be construed to represent all primer manufacturers. But, if every manufacturer uses the same chemicals between their large and small primers – which is almost certainly the case – then the cold-weather behavior of the two primer sizes should be consistent as well.
