VBA code in excel operates inconsistently with very simple code - excel

Question

I wrote some pretty simple VBA (excel macros) code to manage my audio licencing excel experience. The code is supposed to look through the excel sheet in column 3, look for any that have "AMC" in their column, and then copy and paste the row to sheet 2 and continue searching through entire excel document. This code is very simple and worked once right before it stopped working right. It only takes the very last AMC value and puts that on sheet 2 but not the other 5 rows that have AMC in their column 3 value.
Please help! I would appreciate it very much :)
-Jeremy
VBA Code:
Sub CommandButton1_Click()
a = Worksheets("Sheet1").UsedRange.Rows.Count
b = 0
For i = 2 To a
If Worksheets("Sheet1").Cells(i, 3).Value = "AMC" Then
Worksheets("Sheet1").Rows(i).Copy
Worksheets("Sheet2").Activate
' b = ActiveSheet.UsedRange.Rows.Count
Worksheets("Sheet2").Cells(b + 1, 1).Select
ActiveSheet.Paste
Worksheets("Sheet1").Activate
End If
Next
Application.CutCopyMode = False
ThisWorkbook.Worksheets("Sheet1").Cells(1, 1).Select
End Sub

Answer 1

This should solve your problem :
If Worksheets("Sheet1").Cells(i, 3).Value = "AMC" Then
Worksheets("Sheet1").Rows(i).Copy
Worksheets("Sheet2").Activate
Worksheets("Sheet2").Cells(b + 1, 1).Select
b = b + 1
ActiveSheet.Paste
Worksheets("Sheet1").Activate
End If

Answer 2

You could use Instr and Union.
Union is very efficient as you store all the qualifying ranges in memory and then write out only once to the sheet. Much less expensive operation than continually writing out to the sheet.
Instr allows you to use vbBinaryCompare which means you are doing a case sensitive match i.e. only AC not ac will be matched on.
The code belows avoids .Activate, which is again an expensive operation that isn't required.
UsedRange means you may be looping many more rows than required. You only want to loop to the last populated row in column C of sheet 1, as that is the column you are testing. Hence, I use .Cells(.Rows.Count, C").End(xlUp).Row to find that last row.
Use Option Explicit - research why! It will make your VBA life soooooo much better.
Code:
Option Explicit
Sub CommandButton1_Click()
Dim lastRow As Long, sSht As Worksheet, tSht As Worksheet, loopRange As Range
Set sSht = ThisWorkbook.Worksheets("Sheet1")
Set tSht = ThisWorkbook.Worksheets("Sheet2")
With sSht
Set loopRange = .Range("C2:C" & .Cells(.Rows.Count, C").End(xlUp).Row)
End With
Dim rng As Range, unionRng As Range
For Each rng In loopRange
If InStr(1, rng.Value, "AC", vbBinaryCompare) > 0 Then
If Not unionRng Is Nothing Then
Set unionRng = Union(unionRng, rng)
Else
Set unionRng = rng
End If
End If
Next rng
If Not unionRng Is Nothing Then unionRng.EntireRow.Copy tSht.Cells(1, 1)
End Sub