I'm not a gun expert although I have a few books (I'm better versed in ACW arty.)

If I understand correctly, the 1st MSM would have been by far the most heavily engaged of Philips command essentially at the center of the Union line, followed by the 7th and then the 4th MSM farthest to the right/west. This appears to be supported by Buresh's Appendix IV casualty recap. Buresh also posited that some of the 1st MSM was armed with Henry's based on pg. 110 (note 11). His reasoning was that Grover's PEMM at Warrensburg had purchased or been issued some Henry's and that the 1st MSM must have obtained some while they were stationed there as well. Buresh makes broader assumptions about the brigade in general having some of these arms. I haven't examined his sources. I don't have a strong basis, but I find the likelihood of large numbers of Henry's in Missouri at the time, unlikely. Purely speculation on my part but if KY bought 20,000 Ballard's, it wouldn't surprise me if MO ended up with a thousand or more.

Lees' battlefield archaeology study and maps support there being .44 Henry's and/or Ballards at the site. He states that they appeared to be Ballard ammo and not Henry. However, on the basis of Buresh's work he concluded that these must be Henry's since Ballards "are not known to have been used by any of regiments engaged at Mine Creek." Based on what Bruce has found about the 3rd MSM, this might have been a premature conclusion. Of nine cases recovered at Mine Creek, only two relatively complete cases were found. One was unfired, and Lees identified the other as from a Henry (twin firing pin marks) and that came from Doug Scott's survey work a few years previous. So it appears some Henry's were present. Interchangeable ammo makes a mix distinctly possible.

Whether Henry's or Ballards, a clear line of "dropped" unfired ammo of this type is seen and it is in front of the concentration of fired artillery projectiles (Confederate shell and canister) as well as fired Enfield rounds. This marks the heavily engaged portion of the MSM and the center of the Union line. Per Lees' study the primary action took place in the field northeast of the present battlefield park site.

To the right/West there are a large number of Gallager or Smith type rounds (the study figure labels them as Gallagers.) These are most likely from the 4th or 7th MSM. Unfortunately the survey could not extend north onto private land to confirm a Union firing line (unfired rounds and some Confederate counterfire.)