Older Pedersoli 1863 Springfield nipple thread?

I'm looking to replace the nipple on an older Navy Arms marked 1863 Springfield made by Pedersoli in the 1980s.

Would this be a 1/4×28 thread, since Pedersoli had not yet bought out Euroarms at that time?

AIR, ALL Pedersoli threads are metric. It is, after all, a European company.

Their "sporting" weapons like Kentucky, Hawken etc are 1/4×28 (same as T/C ) and some of their muskets like my 1816 Percussion Conversion use the original 5/16 x 24 American thread.

But their newer military Springfield muskets use the Euroarms thread, but the Enfields use another thread pitch that changed in years past. The Pedersoli Whitworth uses still another thread.

So , now I have a 1980s era Pedersoli but I don't know what thread they used. The 8x1 or whatever it is apparently will easily screw into a 1/4x28 which is dangerous, so caution has to be used here.

"The 8x1 or whatever it is apparently will easily screw into a 1/4x28 which is dangerous, so caution has to be used here."

They aren't even close. One mm = .o39", do the math. Did you mean to say the 8mm will screw into a 5/16 - 24? It will but needs to be forced and the pitch is a little different. The chances are you gun is 8mm. A 5/16 bolt has a major diameter of .3125" and the 8mm is .3150

I don't know, I dont have the thread sizes committed to memory , I know one of the metric sizes is nearly identical to a standard English measurement thread but interchangeably using them is horribly unsafe .

Tonite I will try to gently thread in nipples in various sizes I have , including a Euroarms size and at least it's a starting point.

5/16x24 screws in nice and easy, and tight.

.8x1 screws in sloppy and moves around.

I'm gonna check with Pedersoli before I fire this thing, just to be sure its 5/16x24.