I was going to add this to my RL 19 post but decided to just add another topic.
I had my gun sighted in shooting factory Rem core lokts and IMR 4064 powder, the bullets were impacting the same place on the target which was around the bullseye. I then switched to RL 19 loads with the same bullets and primers and they grouped much better, but hit 3" lower and 2" to the right of the others. Does this mean that the RL 19 powder has slower velocity than the others are likely to have???? I know that the others are faster powders than RL 19 on the burn scale chart, but does that mean the ones hitting lower are moving faster or slower velocity wise?? I don't have a chrony and have no access to one. I know this is just a theory question but it is one I am very interested in learning how to read these targets. Thanks
Brian

It would be hard to guess whether or not RL 19 actually has that different a velocity than the other powders. You really will have to chronograph it some time to see.

What is happening for sure is that due to the change in burning rate, the bullet is leaving the barrel at a different point in the barrel's vibration. That is, as the barrel whips due to the bullet and powder traveling down the bore the RL 19 loads are leaving at a different time in the cycle.

This is often seen when switching components in some barrels. I once had a 25-06 barrel that would shoot 87 grain Sierra bullets way to the left of Speer's or Hornady's even when using the same load.

Hope this helps, R F

Grouping in a different portion of the target is not a good indicator of relative velocity with such a change of components. Bullets exitting the muzzle in a diffent node of vibration can account for several inches at 100 yds.

With no chronograph you can get a rough estimate of velocity by zeroing a load at 100 yds then measure POI distance below POA at 400 yds. Repeat for your other load. Play in a ballistic program like JBM ballistics on-line entering different velocity till you match your actual trajectory.

I would about guarantee that your Rel 19 load is going slower than your IMR 4064 load. If we go by charge weights, it will take about 12% more weight of Rel 19 than IMR 4064 to achieve the same velocity.

So if your load was 150 gr bullet and 44gr of IMR 4064, you would need to use ~ 49 grains of Rel 19 to get approximately the same muzzle velocity. IMR 4064 is about optimum for the 308, by the way. Rel15 is a tad slow, but several competitors favor it.

Scott

Bullets impacting lower than a comparison group usually indicates that they are traveling faster, thus they get a milisecond less of upward whip due to recoil. When someone told me this I refuted it for a long time, until I fired enough rounds through my chronograph to verify.



The other guys are right. The harmonic of the barrel are impossible to predict. The bullets will leave the harmonic/whip "cone" (the barrel actually vibrates in a cone shape) at different times. Thus the reason your second group went right as well as down.

Fur,

Would you mind terribly telling my rifles that they are supposed to shoot lower with faster loads!

For instance, my 405 Winchester:

54 gr of Rel7 & 300 gr Hdy (2400 fps)- bulls eye @ 100 yds
62 gr of 4895 & 300 gr Hdy (2300 fps) - 4" low @ 100 yds

50 Beowulf:

40 gr of IMR4227 & 335 gr Rainer (1600 gps) - bulls eye @ 100 yards

42.5 gr of H110 (W296) & 335 gr Rainer (1820 fps) - 6" high at 100 yards. This load is TOO HOT by the way so don't use it!

416 Rigby:

300 gr Barnes X & 107 gr of IMR 7828 (2650 fps) - bulls eye @ 100 yards

350 grain Speer & 104 gr of IMR4350 (2785 fps) - 5" high at 100 yds.

460 Weatherby mag:

500 gr Hdy & 110 gr of IMR 4350 (2360 fps) - 2" low at 100 yds

500 gr Hdy & 118 gr of IMR 4350 (2570 fps) - 2.5" high @ 100 yds. This load is TOO HOT by the way so don't use it! At least it was a sticky bolt maker in my Weatherby MkV!

See, my trouble? My rifles just aren't doing what they are supposed to! It is so very frustrating.

I have more examples, by the way.

Scott