Enfield 7.62x39 barrel

[Bruce_in_Oz]

Careful with those threads.

Both No1 and No4 barrels have the same pitch; 14 TPI, but have very different thread forms.

No4s are pretty much pure "Whitworth" (55 degree) form, whereas No1 (and earlier) breech threads are "Enfield Special" form, 49 degrees 40 minutes, with radiused roots and crests like a BA thread form. Full spec of a No1 thread is:

Outside Dia. .99555" (Dia. across radiused crests)
Root Dia. .9024"
Eff. Dia. .9574"
Pitch .0714"
TPI 14
Angle 49deg 40min
Crest radius .01411"
Root radius .00804"

One of these days I will stuff that data into AutoCad or similar and see if the numbers actually work to five decimal places like it shows on parts of the original paper drawings.

If you want to try a magazine version, have a close look at either Mini-30 mags, or the odd "single-stack" mags that came with the strange "compliance" AK sporters a decade or so back. They appear to have been made in both 5 and 10 round capacity. The trick is to use a mag that seats close to the chamber and is narrow enough to not require machining out of the sides of the receiver / body magazine well, especially at the thin, forward section.

Reliable extraction and ejection are the next challenges.