Thread: Overpressure signs on Belted Mag

Originally Posted by Vandros

Thanks all for the replys - very helpful
Yes was using Winchester Magnum large rifle primer
Definitely not going to go that high again
Didn't have the Chrono working on those ones so don't know the speed but 70 grains usually gives me around 2,830 fps

Greetings Vandros and all,
That seems to identify the problem. Your velocity shows that you do not have a hot lot of AR2217. The test I referred to about the Winchester Large Rifle Magnum primers determined that they gave significant increases in pressure without increases in velocity which I suspect is what you have experienced. I strongly suggest that you stop using them and switch to either Federal 215 or CCI 250 primers whichever you can get. It is possible that even your 70 grain load is over pressure with the WLRM primers. An old Winchester pamphlet that I have recomends the standard Winchester Large Rifle Primer for the 7mm Remington Magnum. I used WLR primers in my 7mm SAUM and got good velocity and accuracy with 68 grains of AR2217 and 150 grain projectiles until I switched to the Federal 215 primers. Winchester primers are formulated for the hard to ignite Winchester ball powders and they are best only used with them.
Regards Grandpamac.