Small Rifle Primer Ignition Question
- Thread starter Phil
- Start date
Hi Phil,
The Lapua 308 Palma uses the small rifle primer, as did the old Remington 30 UBR cases. This was essentially a thin-walled 308 Win case (with a small primer pocket) that was intended to be used to form 7BR, 6BR and any of several other wildcats then in vogue. Some Long Range competitors tried them in competition and found that the small primers were a good bit less "lot sensitive" than the large primers. The Large Rifle primers normally require some serious testing at 1,000 yards to isolate a truly good batch. The Small Rifle primers, not so much. Anyway, they were lamented by this bunch when Remington discontinued them, and hoarded by those who had them on hand. When we introduced the Palma case, it was at the behest of the US Palma team shooters, and it was they who requested we build these with a small primer pocket.
A quick word here; most matches take place in reasonable weather, generally in the summer. Call it 70 degrees and above for a norm. I'd generally plug 45-46 grains of powder as about the limit of good, reliable ignition when using a Small Rifle primer. Slow burning powder, ball powder or very much cooler tempereatures and I think you're setting yourself up for hangfires or outright misfires. We warn against using the Palma cases for hunting applications simply because these factors can all become an issue in hunting ammo. Word to the wise, but no problem as long as they're used within their intended venue.
Hope that helps!
The Lapua 308 Palma uses the small rifle primer, as did the old Remington 30 UBR cases. This was essentially a thin-walled 308 Win case (with a small primer pocket) that was intended to be used to form 7BR, 6BR and any of several other wildcats then in vogue. Some Long Range competitors tried them in competition and found that the small primers were a good bit less "lot sensitive" than the large primers. The Large Rifle primers normally require some serious testing at 1,000 yards to isolate a truly good batch. The Small Rifle primers, not so much. Anyway, they were lamented by this bunch when Remington discontinued them, and hoarded by those who had them on hand. When we introduced the Palma case, it was at the behest of the US Palma team shooters, and it was they who requested we build these with a small primer pocket.
A quick word here; most matches take place in reasonable weather, generally in the summer. Call it 70 degrees and above for a norm. I'd generally plug 45-46 grains of powder as about the limit of good, reliable ignition when using a Small Rifle primer. Slow burning powder, ball powder or very much cooler tempereatures and I think you're setting yourself up for hangfires or outright misfires. We warn against using the Palma cases for hunting applications simply because these factors can all become an issue in hunting ammo. Word to the wise, but no problem as long as they're used within their intended venue.
Hope that helps!
I looked at this question vis a vis the .308W Lapua Palma case in the February and March issues of Target Shooter online magazine (back issues available as free Adobe pdf downloads on http://www.targetshooteronline.com/ and the May issue just gone live.)
Providing the ambient / ammunition temperature is reasonable (certainly above 5-deg C, better still 10C / 50F or higher) it will ignite charges up to 48gn of all powders tried without any problems. Use a SR Magnum / BR primer throughout.
Somewhat to my surprise, the Palma case / CCI-BR4 primer combination did very well with Hodgdon H414 (same as Win 760) ball powder in charges running up to 49.9gn under a 175gn Berger BTLR on a not particularly warm day - 9/10-deg C ie around 50 F. It did substantially better than the same combination in standard Lapua brass + CCI-200 fired in the same range session as a control. The reason for the surprise was that as Kevin says, ball powders are normally harder to ignite than the extruded variety thanks to thicker non-flammable 'deterrent' coatings.
In any given bullet / powder / charge weight combination, the small primer gives lower MVs, usually in the 20-35 fps range and so loads have to be adjusted up to allow for this. In .308 Win, the main benefit for me and other F/TR shooters is that we get better results from heavy bullets >200gn with relatively slow burning double-base powders, primarily Reloder 17 and Viht N550. The Palma case is also very strong and takes a lot of full-pressure firings before the pocket expands and the case has to be scrapped.
I'm not sure how it works out with still slower powders in the N160 / 4831 class in smaller calibre cartridges based on the 308 - .243W, .260R, 7mm-08. There is the occasional query on this forum asking if anybody has necked the Palma case down to these calibres, especially .260 Rem which is very 'in' at present, and if so how does it work out. The response has been small to nil suggesting most .260R users are content with standard large primer brass, especially now that the outfit that Kevin represents makes VERY good quality examples.
Providing the ambient / ammunition temperature is reasonable (certainly above 5-deg C, better still 10C / 50F or higher) it will ignite charges up to 48gn of all powders tried without any problems. Use a SR Magnum / BR primer throughout.
Somewhat to my surprise, the Palma case / CCI-BR4 primer combination did very well with Hodgdon H414 (same as Win 760) ball powder in charges running up to 49.9gn under a 175gn Berger BTLR on a not particularly warm day - 9/10-deg C ie around 50 F. It did substantially better than the same combination in standard Lapua brass + CCI-200 fired in the same range session as a control. The reason for the surprise was that as Kevin says, ball powders are normally harder to ignite than the extruded variety thanks to thicker non-flammable 'deterrent' coatings.
In any given bullet / powder / charge weight combination, the small primer gives lower MVs, usually in the 20-35 fps range and so loads have to be adjusted up to allow for this. In .308 Win, the main benefit for me and other F/TR shooters is that we get better results from heavy bullets >200gn with relatively slow burning double-base powders, primarily Reloder 17 and Viht N550. The Palma case is also very strong and takes a lot of full-pressure firings before the pocket expands and the case has to be scrapped.
I'm not sure how it works out with still slower powders in the N160 / 4831 class in smaller calibre cartridges based on the 308 - .243W, .260R, 7mm-08. There is the occasional query on this forum asking if anybody has necked the Palma case down to these calibres, especially .260 Rem which is very 'in' at present, and if so how does it work out. The response has been small to nil suggesting most .260R users are content with standard large primer brass, especially now that the outfit that Kevin represents makes VERY good quality examples.
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