Primer question

[Klaus Von Richter]

[tdbru]

KVR,
most 6.5 Grendel ammo is shot out of the AR design rifle. it has a floating firing pin. so thick cup primers are recommended to prevent slam fires. CCI450. CCI41, Rem 7 1/2, WSRM, etc. with standard thin cup primers the potential for a slam fire goes up quite a bit.

if you only shoot your 6.5 Grendel ammo out of a bolt gun it won't matter to you which primer you use, pick the one for best accuracy then, or availability, or price.

but if you use an AR platform, it's highly recommended to use small rifle primers with the thicker primer cups to help reduce the risk of slam fires. if you are using an AR and have some factory ammo, next time you're out at the range, load 2 in the magazine, shoot the first one, and extract the second one and look at the primer. you'll see a light dimple from the firing pin since the AR has a floating firing pin design. thin cups up the probability that when the bolt slams home, and due to inertia the firing pin hits the back of the primer, the energy of just the inertial strike of the firing pin will set off the primer. with a thicker primer cup the firing pin inertia doesn't have enough energy to set off the thicker cup primers, it takes the hammer blow on the firing pin to deliver enough strike energy to set off the primer.

short answer, for safety reasons use small rifle primers with the thicker cups for an AR platform rifle.

for a bolt gun, it won't matter.

-tdbru

[grayfox]

Agreed. Magnum primer does not mean use for magnum rifles. It is hotter, but the main reason is a tdbru says, 450, cci41, benchrest primers like br4 and rem 7 1/2, all have thicker cups. Slam fire is a lurking enemy and thicker cups ward it off.
Your choice of primer will affect your MV and maybe ES so re-calibrate loads after changing. But you should Recalibrate any time you change any of your variables.

[1Shot]

With not just the 6.5 Grendel but with most any caliber most loading manuals suggest that you use a mag primer when using any ball powders. They are harder to ignite than stick powders and especially when it gets really cold you need the mag primer to get good ignition. Basically a mag primer has a compound that burns hotter and with a longer flame. As said they have thicker "harder" cups which can withstand higher pressures without deforming primer pockets or piercing. This is one of the reasons that I think that you can not go by primer condition so much to judge pressure signs with the 6.5 Grendel fired in ARs like you can with this round and others fired in bolt rifles. The AR platform is not designed to handle as a steady diet the higher pressures that most bolt rifles are. Basically by the time you start to see high pressure signs on primers in the AR you are already over pressure for what the action is designed for. Slam fire as mentioned is a real concern with any free floating firing pin semi auto. I learned a long time ago with my first M1 Garand certain primers are a NO NO. I was using Federal 210M primers my first time out. First clip I had a double fire. I thought it must have been trigger control related. Rifle recoil rebound causing me to pull the trigger again. Next clip I had it triple fire. An old fellow came running down the line calling cease fire. First question he ask me was are you using Federal primers. I said yes. He said you can't use them in M1s. Then he explained why. I have never had another slam fire with any free floating pin rifle because I heeded his advice. I have seen slam fire once with an AR and an SKS and a few with M1s and M1As from newbie shooters over the years being a range safety officer or just being at a range. Mainly it happens when someone drops a round into the chamber and then lets the bolt go home hard. These rifles are designed to feed from the magazine which slows down bolt thrust. I have used CCIBR4, CCI 450, Rem 7 1/2 and Wolf Mag primers with the Grendel with no problems. With 223/5.56 I have used those and CCi 400 and Winchester SR with no problems also. Federal does now make a primer just for the AR and it is labeled so. Problem right now is finding ANY primers.

[White Smoke]

For a bolt rifle, it doesn't matter. For AR's, I highly recommend the CCI #41 primers. They are specifically made to military specs for AR's to prevent slam-fires.

[FLshooter]