Track of the Wolf lists two nipples in 1/4-28 for T/C rifles ( not Senecas or Cherokees) with cone heights of 0.440 or 0.300. I would get the taller one. Actually, that is the nipple i have on my T/C Hawken. Rifles are less sensitive to cone height than revolvers as the throw stops on the nipple's cone, not the lock plate.
What is important is the thread journal length. One has a thread journal length of 0.195" and the other has a thread journal length of 0.200". Either will work.
@Robertakamagoo has ordered nipples and a mold. So while the new nipple is not yet installed, a replacement has been ordered.