Question on Case Capacity changing brass to Lapua

[HllCntryHrrcane]

In my 300win mag shooting Accubond 180s, I have a load worked up for brass measuring 91 grains capacity, and I am in the process of switching to better and more consistent Lapua brass, measuring 90 grains capacity. With everything else, staying the same, how much do you think I need to drop the powder load on the Lapua brass, to achieve the same accuracy, velocity, barrel, harmonics, etc.? I anneal, full length size, and set neck size and tension using mandrel. Quick load shows to need to drop the powder charge quite a bit to stay in the same velocity and pressure and barrel time. Trying to not completely start my load development search over with a hunting trip coming up.

Thx in advanced!

 

[Straightshooter1]

In my 300win mag shooting Accubond 180s, I have a load worked up for brass measuring 91 grains capacity, and I am in the process of switching to better and more consistent Lapua brass, measuring 90 grains capacity. With everything else, staying the same, how much do you think I need to drop the powder load on the Lapua brass, to achieve the same accuracy, velocity, barrel, harmonics, etc.? I anneal, full length size, and set neck size and tension using mandrel. Quick load shows to need to drop the powder charge quite a bit to stay in the same velocity and pressure and barrel time. Trying to not completely start my load development search over with a hunting trip coming up.

Thx in advanced!

So. . . I'd just drop the charge to match the barrel time you get in QL. I assume you've already adjusted the Ba for the lot of powder you using. You should be close enough that you should be able to make some adjustments without having to "completely start" your load development over.

 

[HllCntryHrrcane]

So. . . I'd just drop the charge to match the barrel time you get in QL. I assume you've already adjusted the Ba for the lot of powder you using. You should be close enough that you should be able to make some adjustments without having to "completely start" your load development over.

Yes sir I have tweaked the burn rate in quick load to match up with my chronograph. That brings me to another question, which is tweaking quick load via burn rate versus tweaking quick load via the starting pressure to match your real world chronograph data will affect barrel time. Not totally sure with quick load which to be adjusting to true it up. I am shooting with bullet sitting death .050 off of the jam.

 

[HllCntryHrrcane]

I have played with Quickload using the stock initial pressure of 3625 and also 9365 per some recommendations of 10825 for jam minus 146 per .005 off and then true. Barrel time and pressure are obviously changed even after truing using the different initial start pressures.

 

[HllCntryHrrcane]

Did a 2g MV ladder test today and surprisingly no change in velo really between cases despite the 1g volume difference. In fact, with just a 1 shot ladder I saw a pretty nice velo flat spot between 75.4 and 76.0. Guess I will shoot a round robin 5 shot test tomorrow and see what I shows.

 

[Straightshooter1]

Did a 2g MV ladder test today and surprisingly no change in velo really between ass despite the 1g volume difference. In fact, with just a 1 shot ladder I saw a pretty nice velo flat spot between 75.4 and 76.0. Guess I will shoot a round robin 5 shot test tomorrow and see what I shows.

Be aware . . . velocity flat spots for 1 shot ladders really doesn't tell you anything. If you were to shoot the same ladder 2 or 3 more times, in each case you'll very likely find very different flat spots.

 

[HllCntryHrrcane]

Be aware . . . velocity flat spots for 1 shot ladders really doesn't tell you anything. If you were to shoot the same ladder 2 or 3 more times, in each case you'll very likely find very different flat spots.

For sure. I dont use flat spots to tune or developed but was surprised to see it here and little velo change between case volumes. Was prepared for a 1g drop. Will see what the target tells.

 

[HllCntryHrrcane]

Did some testing today and suprisingly the happy/accuracy powder load node did not change from case to case. Again, surprised, but believe the target...I was expecting a .5-.8g drop needed. Got to work up some math to see what the averages, ES, and SD were across the tested powder loads, but the group liked the same powder load. Dunno