Home Forums Reloading Big Game Rifles why do powders vary so much in different guns

The reason I am asking is I have been experimenting with different powders for my Fw 7-08. From what I have been reading big game and mag primers are supposed to be a good powder but my results have been terrible. Last weekend I ran three different powders ( minus) the mag primers and the big game was the worst but Varget and R15 were close. Today I loaded up 140 grain partitions and 47 grains of 139 hornady with H4350 42 grains but the big game was 6 inches lower no chrono today. But I am guessing they were no where near the velocity. So what makes the difference from gun to gun. My results with 120 grain Varget were around 2950 @ the big game were around 2830 again no mag primer. I have no complaints with the Varget just curious.

Well, let me throw this out to blow your theory to bits: faster loads often hit lower on target at 100 yards or so.

#1 rule of rifle reloading -- no guessing.

Where changing components, where one load hits on the paper in comparison to another load is not relevant. It provided you with no meaningful data to compare different loads.

Find a load that gives you the group size and velocity you desire, then turn the turn the dials....problem solved....

Anything you change can change barrel harmonics, and size every barrel is different, each has it's own harmonics. Consequently they can be as fickle as women. No use arguing with either, just figure out what they like and give it to them. It will make your life simpler and easier in the end.

... and velocity cannot be predicted by comparing how high or low the bullet hits the target.

Harmonics.
http://www.varmintal.com/amode.htm

Words of wisdom, my friend, words of wisdom.

I will run them though a chrony. Kitch That is something I can get my head around the fickle part.:)

Well, you can get a pretty good idea of its directional component.

The 308 would have to drop 6 inches in 100 yards meaning
it was traveling about as fast as a 22 lr. Think about it
it has to be the vibrations, or something mechanical like
a loose scope.

I hate it when someone says tells me, "It is what it is" but in this case "it is." There's no rhyme or reason why one powder will have widely different points of impact from another even at 100 yds. The same thing happens when shooting different brands of bullets with the same powder charge.

I've even seen 4-5" difference even when shooting the same brand and same weight bullet but of different design. I have a favorite load for my .30/06 that uses a 180 gr Accubond and I wanted to see if I could use the 180 gr Ballistic Tip for practice. Same cases, same primer, same powder and charge weight, same distance off the lands.....no luck; they were 3" left and 2" lower.

As mentioned above, chose the one that gives the accuracy and velocity you can live with and run with it.

I have a rifle that will change POI as much as six inches with just a primer change.
As was said above it's in the harmonics and where in it's arc the bullet leaves the barrel.