Thread: Overpressure signs on Belted Mag

Greetings Vandros,
The front of the belt is not supported by the solid case head and can expand more than the rear. This may have contributed to the odd mark. The 7mm Rem Mag often shows quite wide variations in pressure and the best evidence of this is velocity. Your 71 grain load should develop about 2,850 fps in your 21 inch barrel so if your velocity is much more than this your pressure is higher. Your PPU cases may be the culprit if they are significantly heavier than the US cases. Also you don't mention the primer you have used. The Winchester Magnum large rifle primer can produce high pressures with AR2217 and other stick powders based on pressure tests in Handloader a few years ago. Also the ELDX is a long projectile that will seat deeper into the case which will increase pressure. Loads over book max probably should not be explored by someone just getting into handloading. Dropping back to 69 grains of AR2217 would reduce velocity by around 70 feet per second which the deer will never notice. Keep up the handloading, a thoroughly worthwhile pastime, but please take it slowly.
Regards Grandpamac.

Originally Posted by grandpamac

Greetings Vandros,
The front of the belt is not supported by the solid case head and can expand more than the rear. This may have contributed to the odd mark. The 7mm Rem Mag often shows quite wide variations in pressure and the best evidence of this is velocity. Your 71 grain load should develop about 2,850 fps in your 21 inch barrel so if your velocity is much more than this your pressure is higher. Your PPU cases may be the culprit if they are significantly heavier than the US cases. Also you don't mention the primer you have used. The Winchester Magnum large rifle primer can produce high pressures with AR2217 and other stick powders based on pressure tests in Handloader a few years ago. Also the ELDX is a long projectile that will seat deeper into the case which will increase pressure. Loads over book max probably should not be explored by someone just getting into handloading. Dropping back to 69 grains of AR2217 would reduce velocity by around 70 feet per second which the deer will never notice. Keep up the handloading, a thoroughly worthwhile pastime, but please take it slowly.
Regards Grandpamac.

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

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.