Reply with quote #1
I want to reverse engineer the Ammo, which has a velocity of 2790 fps per Lapua. So I took a cartridge apart.
Well the powder is 30.3 grains of something. The COAL is 2.322 which is lower than the 3.362 in the manual.
I ran the numbers with N140, N150, N540 and N550 and some others just to check.
Per Quickload the N140 has a velocity of 2793 out of a 26 inch barrel.
Now the Max load in the VV manual for the 105 Scenar is 28.9 grs for N140 though QL shows 30.3 being close to max.
The Max in the manual for N540 is 30.4 but QL is showing high pressure at 30.3, additionally the predicted velocity is 2828 fps.
N550 velocity is 2689, and N150 velocity is 2752.
Visually I cant tell if it is 150, 540 or 140 since they look about the same.
N-135 and N-133 are showing way too much predicted pressure and velocity.
Also ran numbers for N160, N165, 560 and they dont come close to the velocity at the given charge wieght.
So my plan is to load 5 cartridges each with N140, N540, and N150 and go test at the range and see what happens.
Do you think it is a reasonable assumption and approach. All hinges on the following:
Lapua is using one of their commercially sold powders, and not some other manufacturers powder.
Reply with quote #2
Here is the speed I got from the factory ammo out of my 26 inch Shilen.Almost 100 fps than advertised.
Factory Lapua 90 gr – 2978 / 2935 fps
Factory Lapua 105 gr. – 2894 / 2883 / 2907 fps
Reply with quote #3
It's a bad assumption. Lapua (VihtaVouri) manufactures and uses many non-canister powders. Factory ammo (of all types) is loaded to a pressure specification, velocity is secondary, powder lots vary so quantities are adjusted to make the pressure spec.
Reply with quote #4
Lapua states that their powder choice and weights are in the ranges presented in their reloading guides. However they do not publicly state exactly which powder or load is used.
It is an experiment in any case, who know maybe I will strike the right load. Then again pigs might fly someday.