Nipple Threads

[52Bore]

Thinking of threads - especially for rifles (I'm not a pistol guy).
Seems 1/4-28 is the standard for #11 rifles. OAL and thread length vary with pistols and slightly with rifles that have drums.
I've made a few M6-1.0, but very few.

5/16-18 with a musket cap is common on percussion military style rifles (including original Parker Hale's).

Here is the one that confuses many. 5/16-20; when PH sold off and things started to be made in Italy - it's actually a M8x1.25, even todays Euroarms as well as Navy Arms and Pedersoli.
8mm = 0.315" vs 5/16 = 0.3125" (0.0025", 1/2 the thickness of a hair on your head..) M8 is larger.
1.25 is 20.32 tpi. vs 20. This is Treads per Inch. Since the threads are roughly 1/4 inch long = 5.08 threads. vs 5.
They are virtually interchangeable theoretically, throw in tolerances and they are.

Like IDlewis, 24tpi is seldom seen.
I've made some 1/4-30, 1/4-32 and 12-28 for originals over the years..

 

[Idaholewis]

52, it is an odd deal? I knew better than to take this nipple over to BACO without knowing exactly what the thread pitch was myself, Good bunch of Guy’s that work there, but they wouldn’t have known? I first called Navy Arms themselves and asked if they had any record? They had no clue whatsoever? I took the nipple up to the hardware, i was Confident it was either 5/16 or Metric M8, There is a wall board in Ace that you can test fit a nut, or bolt for thread. The ONLY one it fit in was the 5/16-24 and it was a perfect fit, it wouldn’t even start in the others, I tried them all, even tho it fit perfectly in the 5/16-24 i wanted to see how close it was the other way? (Metric M8) it was No Go in anything else

I even took a picture so I wouldn’t forget

 

[Idaholewis]

And of course when i got over to BACO they didn’t have what i needed in stock, they had the 5/16-24 (Oversize) but not the Regular? I went ahead and brought 1 of the Oversize home to check, but it was NO GO, and I wasn’t about to force on it. I take it the Oversize must be for an older gun with wallowed out threads? They didn’t know over there? All they knew is that’s what they had in stock. I ended up ordering 2 Treso/Ampco nipples from Jedediah Starr that take the 11 Caps. This original nipple is brass, and the Flashhole is BIG, like .040, i am thinking it might have been drilled out? I wouldn’t even shoot it like this for fear of it going half cock, or worse. I am confident this rifle is new unfired, if someone did shoot it, they were DARN good at cleaning it back to new