308 Win vs 308 Palma

[Raifuru]

Just browsing through the net I saw there was a chambering for 308 Palma. Looking on the net I found that there didn't see to be a definitive as to what the difference was. Lapua seemed to have the answer in that their 308 Palma uses a small rifle primer. The rationale being that the small rifle primers are far more consistant than the LRPs. Also as in the 6.5 x 47 the ability to cope with more pressure. If that is the case, could you use the 308 with the SRP in a standard 308 action? Realistically, would it do much for the accuracy potential?

[gbal]

Yes,and no.

[Laurie]

You may be confusing two things here.

 

1) There are two or more 'Palma chambers' and finishing reamer designs to produce them. The 'Palma 95' chamber was very popular with American Fullbore / Palma shooters until the newer 155gn Sierra MK #2156 was introduced, but has been supplemented by one with a longer freebore to suit the longer bullet - longer that is than the earlier 155gn SMK #2155.

 

2) Lapua makes a 'Palma' version of its 308 Win case, identical to the standard version except that it has been machined for the Small Rifle primer and also uses the PPC, BR etc small dia. flash-hole (1.5mm v 2.0mm). The rationale was that the use of a magnum or BR SR primer reduces velocity spreads and hence elevation variations at long ranges. Lapua has been licensed to use the jealously guarded and trademarked 'Palma' name as it undertook the original work and prototype production at the request of the US Palma Teams organisation. It does work, typically reducing ES / SD values by around a third compared to an equivalent loading with a conventional large primer Lapua case. It also changes the charge burn characteristics, typically needing a half grain additional powder to achieve the same MV as the LRP brass, but I have known it to vary by a full grain or even slightly more. The downsides are that the 'weaker' ignition may not suit some hard to ignite (usually ball) powders, and the SR primer is inadequate for very low temperatures. Depending on the powder, this effect may kick in at ~5-deg C down to around freezing. As a result, Lapua says the case is 'unsuitable for hunting', although that should perhaps read unsuitable for winter deer season type hunting. So far as ball powders go, I tried Palma cases and the CCI-BR4 primer with Hodgdon H414 in single figure temperatures a year or two back and had good results, but had major problems a couple of weeks ago with Italian Fiocchi SR primers and Hodgdon CFE223 ball powders under both 155 and 178gn bullets in ambinet temperatures around or just below 10-deg C. Two cartridges failed to ignite at all although demilling and depriming them shows the primers had fired and weren't duds, whilst several produced slight hangfires. The resulting MVs were shall we say unusual to the point of being scary, although nothing produced excessive pressure symptoms.

[Raifuru]

Thanks for that Laurie, obviously not a simple improvement. So in theory, extruded powders and a mag or BR promer should work quite well? It's worth a play I suppose.

[Laurie]

For match use, I'd not buy standard 308 brass now. If you anneal every few firings, or can have somebody do it for you, the Palma brass not only gives better results but lasts forever so you get the extra cost back and some. By contrast, primer pockets loosen on standard cases after half a dozen firings with a 'stout' load. With mild loads, there's a lot less between them.

 

If you do try the Palma cases, remember you also need a small dia. decap pin. The standard pin has a diameter just over 0.06" whilst the nominal diameter for the small flash-hole is 0.059" leading to a stuck or broken pin. The Lee decapper die is robust enough to cope but will swage these flash-holes larger which is a BAD thing.

[gunnery]

i second what Laurie has just said i use small rifle primer brass .308 and Anneal every second firing and it is lasting a long time keep using my same 22 rounds in comps FTR and pockets still tight after 8 firing and still going

[baldie]

The problem with running srp in a rifle designed for lrp,s is firing pin thickness.

 

My actions have a smaller diameter pin for 6.5 x 47 srp,s. We tend not to use them with lrp,s.

 

I haven't ever sectioned a primer, but they are bound to have different anvil sizes.

 

.308 palma is a better chambering for a repeater , as it will put most bullets onto the lands from an AICS magazine. IE , it has a shorter throat than .308 win. At least my reamer has.

[Leeman]

The problem with running srp in a rifle designed for lrp,s is firing pin thickness.

 

 

 

Personally I haven't found that to be a problem, going from large rifle primers to small rifle primers in rifles as diverse as Ruger no.1s to Remingtons and RPAs. The problem I experienced (with a Rem 40X) was excessive firing pin clearance in the bolt face which caused blanked primers even on relatively mild loads compared to using large rifle primer brass which hadn't even raised a mild crater. Different brands of primer, but the small rifle primer seems to demand minimal clearance in the bolt face. Bushing the firing pin solved that problem.

 

Richard.

[gbal]

"yes,and no"-expanded!

 

Yes-Lapua Palma brass can be fired in normal 308 chambers-but see Laurie's decap point if reloading,and maybe Dave's firing pin point.Also cold ignition etc.

 

"no"- Palma small primer brass will give more firings-prob because more brass around to resist primer pocket stretching under pressures (ther may be more if load needs increasing-see Laurie) but overall,better case life. But accuracy potential -expanding a little on Laurie-it eems the small primer case gives more consistent pressure/muzzle velocities-and as Laurie says,that means reduced maximum spread and probably SD for velocity-hence reduced vertical.....at long range.

 

For short range,it's worth bearing this in mind:

 

6mm@3000fps 80g : a 10 fps velocity change means a .16 inch elevation change at 300y.

 

308 will differ,of course,but the point is that at short range,any SD gains from 'small primer' case will be ...small !

 

So probably not worth the downsides in the "palma' case-for short range.Long range,well worth trying.

 

gbal

[Vermincinerator]

I too have not had any problems with standard "large primer" firing pin and small primers, my Stiller started life as a 22-250 AI and is now a 22BR.

600 rnds later it is still beautifully accurate and performs flawlessly

 

Ian.