some 44-77 questions

[Nuclearcricket]

Just out of curiousity I took my 44-77 roller to a match last month to have it weighed. About 10 1/2 pounds, pretty close to what I had figured. One of the shooters was interested in the caliber and was interested in shooting it. I took it along to the match for him to play with today. Good chance that a 44 is in his future.
I do have a question about vertical dispersion. The windage held all the way to the rams but the vert was kind of all over the place. The load was brand new brass, captec, CCI BR2 primers, 74 gr CTG Goex, 480 Gr greaser, ,030 lpde wad and a wax paper wad. Bore was wiped between each shot. Most notable it would thow a couple of shots low and then a high one, enough to shoot under and then over the rams. Any suggestions on what may cause so much vert and what I can do to make it go away?
I would guess that the horizontal was less than a minute as several shots were between the rams legs.
Other than that, the load seems to shoot fairly well and it sure seemed to have a good bit of zip to it. All of the targets that were hit went down quickly. One turkey was hit in the breast and it was driven straight back off of the stand.
Thanks for the help
Sam