Odd results? Question related to powder quantity

[rtracer13]

I was trying out various powder amounts for my .303 brit to get one with the smallest moa at 100 yards. Lee's 2nd edition manual recommended a minimum 40.1 gr for 180 gr bullet of reloader 15.. and make of 45.. so I made 20 rounds at 40.1 gr, 20 rounds at 42.7 gr, and 20 at 39.1 gr.

Out of these 3 loads the 39.1 was by far the most accurate. and the 42.7 gr was hitting low (to the point where a lot of rounds didn't hit paper).
I'm new to reloading so perhaps this is to be expected, but I would have thought 42.7 gr would have higher velocity and be more likely to shoot high rather than low..

I kept a couple rounds to make sure I hadn't mixed up the order and remeasured them.. the 42.7 gr were definitely the low-shooters.

edit: oh forgot to mention, the day I was shooting was in the mid 20c. This may have played an effect.

 

[Dogleg]

With a lot of rifles, barrel whip plays a bigger part in POI than velocity does. This is what you're seeing.

 

[rtracer13]

With a lot of rifles, barrel whip plays a bigger part in POI than velocity does. This is what you're seeing.

So if this is the case, I should likely focus any further load changes around the very minimum load to reduce barrel whip correct? Or is it possible that the barrel whip would be reduced in higher loads as well?

 

[Dogleg]

So if this is the case, I should likely focus any further load changes around the very minimum load to reduce barrel whip correct? Or is it possible that the barrel whip would be reduced in higher loads as well?

It's entirely possible that you will find another sweet spot at the higher end of the powder range, it's more about timing the whip than minimizeing it. When a barrel switches directions it stops for that instant, just like a piston in your your trucks engine.
There's nothing wrong with a mild accurate load for an old rifle.

 

[Ganderite]

Accuracy is group size. Do you want the smallest group? Then experiment around the powder charge that got the best group. it does not matter where it grouped. That is why the sights are adjustable.

If you are using a lee Enfield, they almost always shoot hotter loads lower. make sure the main action screw in front of the magazine is tight.

 

[rtracer13]

Accuracy is group size. Do you want the smallest group? Then experiment around the powder charge that got the best group. it does not matter where it grouped. That is why the sights are adjustable.

If you are using a lee Enfield, they almost always shoot hotter loads lower. make sure the main action screw in front of the magazine is tight.

I am wanting to go for accuracy. The 42.7 load had some on paper and some in the dirt though, so I believe I can safely say that wasn't one of the better loads.
Never the less, good point to consider.

 

[H4831]

I am wanting to go for accuracy. The 42.7 load had some on paper and some in the dirt though, so I believe I can safely say that wasn't one of the better loads.
Never the less, good point to consider.

With a "group," as you describe, some on the paper, some in the dirt, you have a much greater problem than barrel vibrations, or a small change in the charge of the powder.
Either you or your rifle needs help.

 

[rtracer13]

With a "group," as you describe, some on the paper, some in the dirt, you have a much greater problem than barrel vibrations, or a small change in the charge of the powder.
Either you or your rifle needs help.

The 39.1 gr were a decent grouping though. I'm not going to discount that it may be myself or the rifle, but the rifle has got 2" groups at 100 yards with factory ammo in the past (i'll doublecheck nothing has come lose though) and I had a buddy making sure I wasn't flinching when I was firing after I saw the first few hit the dirt.

 

[mmattockx]

I'm new to reloading so perhaps this is to be expected, but I would have thought 42.7 gr would have higher velocity and be more likely to shoot high rather than low..

As the others have explained, the barrel whips around and POI will change all over the place.

The pic shows some load testing I did with my .338 Win Mag. The top left group was from a separate batch, but the other 7 show progressively higher charge weights, all shot on the same day under the same conditions and with no changes to the scope zero. You can see the groups clock around and shift POI all over, there is an especially abrupt shift in POI between the 77.0gr and 77.5gr loads (the middle two on the bottom row).

Mark