Peterson's .22 Creedmoor SRP brass is specifically built for long-distance predator and varmint hunting. This is a low-recoil, flat shooting, wind-bucking round; deadly accurate up to 800 yards. Plus, the round is just straight-up fun to shoot.
 

The brass has increased head hardness so it can tolerate higher pressures. Peterson also increased its internal volume slightly so it works better with the slow-burning powders (like RL 26, or H1000) which shooters tend to favour for this round.
 

Prior to the introduction of Peterson's .22 Creedmoor, shooters had to take 6mm or 6.5 Creedmoor casings and neck them down to .22. There are a few problems with necking down. When you take a larger calibre with the correct neck wall thickness and neck it down to a smaller calibre, that excess brass bunches up in the neck. It creates a tension band, what some people call a doughnut of brass in the neck, which has a negative effect on loading, bullet release and accuracy.
 

A trait of cartridge brass is that it work-hardens – which is to say the brass gets harder each time you “work it.” So the effect of necking down a casing which has been properly annealed, is that after you “work” it, it is no longer properly annealed.
 

Finally, necking a larger calibre into a smaller one results in neck walls that are too thick. The ideal neck wall thickness for a case the size of .22 Creedmoor is .0143 to .0148. Necking down results in neck walls thicker than that. Peterson .22 Creedmoors all fall within that ideal spec.

Small Rifle Primer (SRP)

Many competitive shooters prefer Small Rifle Primer pockets (SRP) because they experience longer primer pocket life due to the increased material in the head of the case. There is also a belief that Small Rifle Primers produce a more consistent ignition. Some people even report better groupings and lower velocity spreads.

However, SRP are not recommended for shooting in extreme cold or hot temperatures. And Small Rifle Primer Brass sometimes requires the firing pin on your gun to be bushed. This depends on your rifle and your bolt. If that is not done, you risk getting pierced primers. 

To make sure you don’t have any problems shooter should talk to their gunsmith and understand what their rifle is set up for before using SRP brass.