Anyone use 7.62x54R Bullets to reload 7.7 Jap?

[FrankenMauser]

My understanding is that it is impossible from a practical standpoint to re-barrel one of these rifles even if you have the spare barrel off of some other T99 rifle (e.g., by buying one on GunBroker, etc).

No.
It is no different than rebarreling a Mauser with a take-off barrel.
Same procedures. Same checks. Same inspections.

Where the "impractical" aspect can come into play is rebarreling with a commercial barrel blank. Type 99s have a thread pattern close to, but not quite, 1.050" - 17 tpi (and always between 50 degree and 60 degree V-thread; but not consistent). Many gunsmiths have a hard time replicating it, or just don't want to try. And the problem has only gotten worse with real gunsmiths retiring and giving way to a world of AR and Glock parts swappers. The few that do try it often don't try to replicate the existing thread pattern. Instead, they just cut 1.050" - 17 tpi and crank that barrel into the receiver so the receiver threads swage the barrel threads to match.

Type 38s and Type 44s are a little better, with at least an understandable metric pattern of M26x1.75mm 60 degree V-thread. But, again, most 'smiffs won't or can't cut it.

But for take-off barrels, it generally is not a problem. Yank the barrel, clean up the receiver and replacement barrel, spin the replacement in, check alignment, clocking, and head space, and adjust if necessary.

[Unclenick]

17 TPI is 1.494 mm. I would guess they may actually be a 1.5 mm thread (16.93 TPI) and that would certainly explain some of the difficulty. I've got a little 1/4" 55° lathe threading bit for threading barrel blanks for my 98 Mausers. Brownells still sells it if someone needs to thread a blank for a 55° profile thread.

[valleyforge.1777]

Thanks for correcting me, sorry if I misunderstood other info I'd gotten at another time. Thanks, too, for explaining why I was wrong.

I was (still am? not sure...) trying to put a 7.7x58 Japanese T99 barrel onto a Browning BAR or Remington 7400 action to convert it to a semi-auto 7.7x58 Japanese rifle. Even found a relatively decent barreled action-only for a BAR in 30-'06 but lost that auction to someone else.

[44 AMP]

I was (still am? not sure...) trying to put a 7.7x58 Japanese T99 barrel onto a Browning BAR or Remington 7400 action to convert it to a semi-auto 7.7x58 Japanese rifle.

I think that's going about it the wrong way and will be more work than worth.

Waste of time trying to fit a WWII surplus Jap barrel onto the Browning or Rem action. May not even be possible.

Get a barrel made to fit the action you're going to use (with the correct shank size and threads), and have it bored and chambered for the 7.7 x58 Japanese cartridge.

[Drm50]

I’m in process of selling out my stuff due to health. I just sold my 7.7 Jap dies and Norma brass on Cast Boolits. I never loaded 7.62 X54 for Mosin. I had Win 1895. It shot lousy with .308” and .311” jackets. The Jap 7.7, Brit 303, Bel 7.65 all did well with Sierra .311 bullets. The 7.7 Jap was one of first military cartridges I loaded. My dad brought one home WW2 and in early 60s bought a box of Norma ammo. He cried about the box of shells costing more than rifle was worth. At the time he was right. Any way I got a set of used dies and loaded 30cal 150gr bullets and they shot all over. The rifle was ugly but would shoot well with 311 bullets.