Actually, you can get a different velocity with different shooters. It all depends on how much of the initial recoil energy they absorb. I proved it to myself by changing my grip when I was recording some pistol rounds and noticed a definite change in velocities recorded. Maybe not large, but it was repeatable.Rule3 said:Having different shooters shoot the same round? That has nothing to due with statistical validity of velocity?
The human factor does not change the load. Accuracy yes. A true test would lock the firearm in a ransom rest of test chamber and as mentioned extreme temp changes if you live in an area that has them.
Actually, you can get a different velocity with different shooters. It all depends on how much of the initial recoil energy they absorb. I proved it to myself by changing my grip when I was recording some pistol rounds and noticed a definite change in velocities recorded. Maybe not large, but it was repeatable.
I do this to get powder back readings, and just the opposite to get powder forward readings, then sometimes I shake the gun while level to get powder level readings. There is a definite pattern that most powders follow here.To get an accurate reading point the gun straight up and slowly lower it before pulling the trigger, The powder is then all clustered at the bottom near the primer.
To clarify, you certainly can change the velocity reading by changing the position of the powder in the case. To get an accurate reading point the gun straight up and slowly lower it before pulling the trigger, The powder is then all clustered at the bottom near the primer.
I would have thought so myself, until I tested several like that. For pistols, bringing the gun up from barrel down to level and firing still affects velocity, even with many 75%, and more, load density loads. Very few powders are unaffected by position when less than 100% load density. When I first started testing this, I was really surprised with the results. As I posted, I get different results with powder back, powder forward, and powder level shooting. And the results are generally consistent from load to load. Naturally some are better and some are worse, but PB will give the highest velocity, PF will give the slowest, and PL will be in between the other two. I have only had one powder give more velocity PF than PB, and it has been discontinued. Some are horrible PB, and some don't lose much, but most lose enough to get your attention, and matter when shooting with the barrel in a downward position and shooting longer ranges.A 3/4 case-full of powder isn't positional unless you shoot straight down.
PF can easily lose 100 to 400 (Or more) FPS from PB. The biggest losers are generally low pressure loads with lots of extra case. I had one load that ran 900+ FPS PB and would stick bullets PF.
Essentially for semi-autos, we are always testing "powder forward" as chambering force will slam the powder charge towards the bullet base.1SOW said:When the recoil spring on a semi-auto slams the cartridge home, wouldn't the sudden stop when it seats throw the powder forward? Assume the pistol is level, aimed at a target.
For a Chrony, wood dowels make good replacements for the diffuser rods, 1/8" diameter if I remember correctly.
I shoot10 round groups for accuracy and velocity testing.