257 Roberts +P

[Aberhan]

We all know the +P designation regarding the 257 Roberts refers to the increased SAAMI pressure rating to 58,000 psi. My question regards the Nosler +P rating on Nosler 257 Roberts brass, which I just acquired. Is there a definitive difference between this brass and other 257 Roberts brass? I have noticed over the years that I get case neck cracks more often in my 257 Roberts brass than any other cartridges I reload for. Is the Nosler brass thicker? If so how much would this affect case capacity? Just curious.

 

[Bruce Mc]

There is no definitive difference between different 257 Roberts brass. Different brass have very slight dimensional differences due to brass web and wall thickness. Remington brass has less powder capacity then Winchester and I've found the Nosler brass very close to the Winchester. Some brass is stamped + P and some aren't. All recent brass is capable of + P loads. I use nickle plated Remington brass that is not stamped + P. My loads that exceed 58k show no pressure symptoms. Recent brass marked + P is to identify the factory loaded ammo is loaded to 58k. It is not an indication of different brass than standard pressure ammo. I have no explanation for your increased cracked necks, I have not experienced that.

 

[Blkram]

Regardless of the stamp on the brass, all manufacturers must build in a factor of safety into their product so that it can tolerate additional pressure or stress, as they have no control over the end user. What that factor of safety may be, may well be up to the manufacturer and their risk management protocols, as well as to what SAMMI may stipulate (just not sure what they require, but IIRC it's 70K psi??? ).

As for cracked necks, there are several variables that can cause that, and you would have to eliminate them through analysis of your reloading practices and firearm's particular chamber tolerances, as previously discussed in your other threads.

 

[PJGunner]

As brass gets resized more and more, the stiffer the brass becomes. Then necks crack. You might try annealing the necks of those cases that have survived and see if that helps with your problem.
PJ