Velocity troubles with 7mm mag

[Gills]

I have thought about it. My only problem with fl sizing is when I tried neck sizing my groups where cut in half

 

[Gills]

If I 1x fire every new case I have to stretch them should I use the load I intend to shoot or would any load be ok for this

 

[FURMAN]

I did not read all of the posts but some cartridges/brass combinations will yield up to 100fps difference between new and once fired brass. The new brass absorbs some of the energy so velocities are lower. Once using once fired the pressure and velocities increase. If you had a load figured out with new brass when this happens you will need to lower powder charge to in the once fired cases to match the velocity of the new brass. This seems to be more noticeable with larger case capacities.

 

[FURMAN]

As far as sizing. Full length is without a doubt the best practice. It ensures the case is the same size every time. If you only full length size when the rounds get hard to chamber you will have two problems. The first is you are changing case capacity from shot to shot. The second is you run the risk of a round not chambering in a hunting situation. Consistency is the key to accuracy.

 

[entoptics]

If I 1x fire every new case I have to stretch them should I use the load I intend to shoot or would any load be ok for this

From my understanding, if you intend to fire form, then any load with moderate-high pressure will work just fine. You just don't want to use "light" loads, as they may not fully form the case.

If it were me, I'd at least work on seating depth or perhaps try an array of different projectiles. No sense in wasting the barrel life and components, without getting any other useful information.

 

[eshorebwhntr]

I have thought about it. My only problem with fl sizing is when I tried neck sizing my groups where cut in half

Ok. Good to know. I didn't know you had tested 1x FL sized. I thought you had only tried new and 1x neck sized.

If I 1x fire every new case I have to stretch them should I use the load I intend to shoot or would any load be ok for this

You're likely going to have 2 separate powder charges that give you good accuracy. 1 for new brass and 1 for the fired brass.

 

[Gills]

Ok ic

 

[bigedp51]

So does more volume generally mean more pressure or less

Below with the top .223/5.56 case on the chart at 30.6 case capacity and the bottom case with 28.0 case capacity you can have over 5,000 psi difference in chamber pressure with the same powder charge.

Quickload tells you to get the case capacity from a case fired in "YOUR" rifle for its pressure and velocity data.

NOTE, the larger the case capacity of a given caliber the less effect it will have on the chamber pressure reading. And due to the thickness and hardness of the cases by manufacture the chamber pressures and velocities can vary until the case is fire formed to your chamber.

So the case capacity will have more effect with a small .22 Hornet case than much larger magnum type cases.