6,5 mm Geschichte
6,5-06 6508 Setztiefe
Betreff: Norma URP and 6508
I hope you are all well and happy.
I am puzzled by recent experience with the 6508 (which I take to be the ballist equivalent to the newer 6509). Recklessly and contrary to my habit of incrementally testing new reloads, I loaded up a batch of 6,5-06 cartridges for a rebarrelled Brno ZKK 600 (presumably the chamber dimensions are the standardized A-Square) with a 650 mm barrel.
LM: For You, my Friend, I drew above 6,5-06, just took a 30-06 Case, left L1 and Shoulder Angle, applyed typical 6,5 mm Neck dimensions and: Ha! Here You are. I assum A.A. earlier did just the same.
The average internal capacity of these cases (never fired and once fired in same rifle based on six / six randomly selected WW Super 25-06) is 4,42 g/4,48 g, respectively, of water.
LM: 25-06 Brass may show a slightly thinner Neckwall
25-06 | 65-06 | 30-06
The load data are as follows: 6508; OAL 77 mm, 3,66 g Norma URP, primer CCI-200. Powder metal canister has the following markings: EXP. 3490/99. This can hardly be a date if only for the fact that I am pretty certain I bought the powder after 1999.
LM: It may be have made, before You bought it
Possibly it is a production code/date. I note that on Norma's home page - https://www.norma.cc/us/Ammunition-Academy/om-handladdning/Powder-storage/ - it says
"Where possible, store the powder at a constant temperature, ideally between 12 and 15°C, and a relative humidity of 40–50%. If the air is too dry, it will dry out the powder, which will cause the pressure to be higher, thus affecting performance."
LM: Yes. Siehe Pulverlebhaftigkeiten#Feuchte
I have stored the powder under quite dry conditions and probably at around 25°C.
LM: Oh. Too warm. Every 10°C up or down halve or doubel the Shelf life of Powder. Nitrozellulose ist nicht stabil. Sie zersetzt sich langsam. Nitrozellulose brennt für Gewehrpatronen zu schnell. Deshalb wird die Schießbaumwolle gelatiniert, in grobere Gestallt gepreßt und oberflächlich im Abbrand verlangsamt. Damit das Pulver nicht irgendwann von selbst hochgeht, werden Substanzen zugesetzt, die die Zersetzungsprodukte binden. Die sind aber irgendwann verbraucht. Der Zeitraum ist auf 10 Jahre eingestellt. Deshalb soll man grundsätzliche keine älteren Treibladungpulververwenden.
When sniffing off the canister there is little or no typical powder smell. Cronograph reading of six cartridges was as follows in m/s: 1.160, 1.175, 1.162, 1.175, 1.170, 1.172 with average of 1.169 m/s. Quickload, however, predicts pressure of 4.001 bar and 1.090 m/s. I played a little with QL, increasing powder load until getting 1.174 m/s. The pressure is then given as 5.272 bar which of course is alarming! My guess is that the powder deteriorated during storage resulting in higher pressure as one can read on the Norma page. However the amount of pressure increase I get really does surprise me.
LM: Popped any Primers?
If you have any comments on this I would be happy to read them.
Best regards, Petur, Donnerstag, 13. September 2018 16:04
Betreff: Norma URP and 6508 - addendum
Thank you for your comments and the info on powder shelf life. Obviously I will have to act on it. The primers did not pop. There there was no cratering around the firing pin dent. Some of the primers were a bit flat though.
Again, many thanks for your comments, P, Freitag, 14. September 2018 19:43