Problem with belt cartridge

[Mada]

So I finally went out to the range today to test out my reloads.

I used:
Remington brass
Winchester WLRM primers
H4831
and Hornady 139 BTSPs

I loaded from 56.0gr to 64.0gr in 1.0gr increments

And this is what I have

[Mada]

My best group was the 56g at .619minutes

57.0g was measured to 1.113 lengthwise

58.0g was measured .564 without the straggler up left, What I think is that after the 4th shot, the 5th shot is thrown off. Could it be because of the barrel heating?

59.0 g wasnt included as the group wasnt as good

60.0g had a decent 3 shot group that measured .483, but had two stragglers both right and left of the groups, Im curious to what could of caused it

61.0g isnt shown

62.0g has a 1.279 group measuring vertically

63.0g has 1.113 measuring farthest to farthest

[Mada]

And last:

64.0g which had one pattern on the left that is just one hole, but as you can see the whole grouping is really thrown around. I didnt measure the MOA of this group as it wouldve been useless, but I was wondering what you guys think could be the problem.

[Mada]

This is my first load so I'm asking what you think I should work with to improve, what grain should I work around with to try and find that right load.

Im really liking the 64.0g because of the two shot/ one hole pattern.



Critique me, please

[bman73]

go back to 56 grains and play with seating depth

[Mada]

alllrighty

[Mada]

Do you guys do 3 round test groups or 5? If not, what is it you do?