Cartridge case capacity a factor


Q:  Last  year,  for  the  first time in  40  years  I  purchased  unprimed Lapua .22-250 cases to use in my new Sako Varmint rifle.  I was very happy with these cases until recently. My carefully  developed loads using BM2 powder and CCI primers which originally  showed no pressure signs are: 40gn Nosler B/Tip 35gn BM2; 50gn  Nosler B/Tip 33.5gn BM2; 55gn Nosler B/Tip 33gn BM2; and 35gn AR2208 with the 40gn Nosler and 35gn AR2208 with the 52gn Sierra MatchKing. These loads are extremely accurate. My problem is that I bought Lapua cases because I believed I would be able to get 12-plus reloads from them, but after 5-6 reloads about one third  of the cases developed loose primer pockets and had to be discarded. I’ve heard that you can use less powder in Lapua cases than with Remington and Winchesters cases and get the same velocity, but I find this hard to believe. Can you confirm if  this is true? I’m currently using 33gn of BM2 with the 55gn Nosler, so how much should I reduce the charge to get 3600fps in  the Lapua cases? I intend trying some Winchester and Remington  brass using CCI primers with the same weight of powder to try  them. With careful loading, how many reloads can I expect to get  before they need to be discarded – 5 or 6? What is the best  hunting projectile in the 55gn range? The twist in my Sako is  1:14 inch which I believe won’t stabilize longer heavier bullets.  Finally, should I expect 5000 shots through my Sako before the  barrel needs replacing – or more or less in .22-250?
Lou Brown

A: Your load of 33gn of BM2 with the 55gn Nosler is near maximum; 33.5gn with the 50gn Nosler is 1.5gn below maximum; and 35gn with  the 52gn Sierra Match King is about 1/2gn over maximum. So it is  not surprising that with the hotter loads your cases are only lasting 5 or 6 reloads. This is perfectly normal. It is not just  a matter of buying the best brass, but rather how high the  pressures of your reloads are going to be. I’ll betthat cases used with 33.5gn of BM2 with the 50gn Nosler are lasting longer  than the others because chamber pressure is lower. Different  brands and lots of cases do vary in weight and therefore capacity, thus you may indeed get the same velocity in Lapua cases with  a grain or so less powder than what you would use in  Winchester or Remington brass. Some Norma cases I’ve used held quite a bit more powder than other brands – up to 10 grains in  7mm Remington Magnum. It is a good practice when getting a new batch of brass, whether it is the same brand or another, to  reduce the loads you’ve been using by 2 grains then work back up. This is because even a fresh lot of cases of the same brand may vary slightly in weight and capacity. My little crystal ball is on the blink again, so there is no way I can tell you how many reloads you are likely to get from any case. I’d stick with 55gn bullets for varmint/predator work, but the standard 1:14 inch  twist of your Sako .22 2-50 will stabilize the heavier Hornady 60gn soft-point and Speer 70gn semi-spitzer which are a lot more effective for pigs and goats. Barrel life is dependent on several factors. The quality of the steel, how well the bore is cleaned, the pressure of your reloads and how hot you let the barrel get. Firing long strings of shots overheats the metal and reduces barrel life. There is no way I can predict how long the life of your barrel is likely to be, but with proper care, I’d expect  around 3000 rounds before field accuracy starts to drop off.

 

 

 


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