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I'm shooting a 300 WSM with 165 gr Nosler AB over 60 grs of RL-15 and CCI 250 primers. I loaded up 10 rounds in Federal and Winchester brass. I was very surprised at the difference between the two. The Federal shot 40 fps faster (3070) than the Winchester brass and it shot 2" higher. Both are sub MOA. Ballisticly the 40 fps difference wouldn't make it shoot 2" higher.
Has anyone had any similar experiences?
I shot 1 round of each - 1 Win., 1 Rem & 1 Fed from my .243. They were all loaded identical with 41.7gr of 4895IMR. They made a perfect diagonal line 1.5" long. They made a 45 degree line.
Today I shot 3 rounds of Rem - perfect cloverleaf.... I shot on top of that 3 rounds with Fed brass. A reasonably tight group 1" away from the cloverleaf.
Different brands of brass will act differently with respect to ballistics.
It seems more prominent in smaller cases like .243 & 7mm-08. The 30'06 & 26'06 cases don't seem to be as sensitive to different brass mfg'ers
Frank in Fla
Yes it the different case volumes that do this.
They probably also result in different neck tension which would better explain the shift in POI than the difference in case volume.
Really if you have less volume with the same load doesn't that make more pressure same as more neck tension so there might be two things right there that are the problem ;-)
I think helotaxi is correct. The Federal was new brass while the Winchester was twice shot brass.
Thanks gentlemen...
I've also experienced the velocity difference in 300WSM brass, the increased velocity is due to less case capacity, in some cases Federal and Remington brass can hold as much as 4gr. less water than Winchester brass, this equals lower pressures with the same charge in the Winchester and less velocity for the same charge. Keep in mind, though, that because of this difference, Winchester can be loaded with a bit more powder (I have Winchester loaded with 1gr. more powder than Remington and .6gr. more powder than Federal), this bit of extra powder means more velocity is achievable with Winchester brass at the cost of extra powder.
I personally love Winchester brass in the 300WSM, as well as Norma. I dislike Federal since it only lasted me 4 firings before the primer pockets became too loose, and I absolutely hate Remington because I couldn't seem to get them past 3 firings. Of cours, ymmv, but this is my experience.