1.) The Curtis report referring to these 25 pieces of Artillery croosing the Mississippi in Arkansas on July 20th, '62. I had thought that Curtis was referring to Parson's crossing of the Mississippi in this report but surely Curtis wasn't that off in his dates on his report.
2.) Bull's diary reporting the crossing of 100 wagon of supply with Parson Infantry Brigade on July 31st, '62. Bull does not mention any Extra artillery on his crossing only his battery. Hindman elludes to a "secret" operation at this time in the Hindman Telegraphs Copybook. He also states to send the supplies on to Little Rock.
3.) The capture of the Steamer "Fairplay" at Vicksburg and the 16,000 arms being shipped to the Trans-Mississippi. The investigation of the incident and the correspondence between Holmes and Sec. of War. Randolph at quite enlightening. The inventory of the arms captured on the "Fairplay" in the Federal Reports indicated that these were castoff weapons from the east.
I am sure that there were other smaller shipments as indicated by the "Fairplay" incident for certainly other arms were shipped by other methods and ships to make up the 11,000 arms not captured on the "Fairplay".
During the Peninsula Campaign Lee's Army of Northern Virginia captured 40 pieces of Federal artillery and 30,000 arms. Lee refitted his army with these better weapons and returned the older weapons his army had been using to the state armoury. It was from there and those 'battlefield pickups' that these 25 Pieces of Artillery and 16,000 arms were drawn from. If you will notice the Table of Organization of Hindman's army at the Battle of Priarie Grove almost all of Hindman's artillery was 12 pd Mountain Howitzers, 12 pd field howitzers and 6 pd smoothbore guns. These were not a suitable match against the Union field artillery during the Peninsula Campaign, or for that matter of fact even against the Federals at Priarie Grove. The Confederate Offensive during the Peninsula Campaign was noted for its ineffective use of artillery. Some of that ineffectiveness could have been the type of artillery Lee had for service at the time.
Another hint is that other strange weapons appear in the Trans-Mississppi particularly in Louisiana. To be specific two Ellsworth breechloading rifled artillery pieces which were part of a group of 20 such guns taken from Harpers Ferry by Stonewall Jackson in September '62 during the Sharpsburg campaign. Certainly those weapons could not have been sent to the Trans-Mississippi prior to late October '62 at the earliest.