7.7 jap

[tbierley]

I have a large lot of Russian HB ammo and I read some were that you and use the bullet and powder charge in the 7.7. I sluged the bore of the 7.7 and it is .311 and the HB is .310. What I worried about is the powder charge.

[dualsport]

It would be pure guesswork to attempt using the powder from the Russian ball in a 7.7 Jap. Not saying it can't be done safely, but it's uncharted territory. Might not be worth it.

[Larry Gibson]

The 7.7 Jap and the 7.62x54R have very, very close to the same case capacity to the base of the cartridge necks. Theoretically it is feasible. However, there are other things that effect psi; throat, types of L&Gs, dimensions of L&Gs, etc. Just to be safe I would drop the powder charge 10% from the 7.62 cartridges and work back up to the original weight of powder. Of course if pressure signs appear in the 7.7 Jap I wouuld definately stop and back off a tudge. The bullets should work fine and it's easy enough to just put the 7.62 powder in a jug and then throw charges in the 7.7 as in normal loading.

As mentioned; unchartered territory with the lot of 7.62x54R you are using and the 7.7 Jap rifle you have. Use caution if you attempt it. If I had plenty of 7.62x54R and not enough 7.7 Jap for my rifles I might just try it myself. I would work up to it as mentioned though.

Larry Gibson

[Japlmg]

I have been doing so for the last 25 years, to feed my Japanese MG's.
I reduce the powder charge a couple grains just to stay on the safe side.
I have never seen pressure signs, and the resulting load functions well in my MG's and rifles.
Gregg

[TommyT]

I've been doing this for years with Hungarian and Bulgarian HB ammo. I pull the bullet and reduce the powder by 10% to start.

[sukivel]

Can anyone recommend a good mould and load to go with it for the 7.7 Jap? I would like to dedicate it to hunting with lead.

Also, I mic'd a pulled bullet out of one of my factory loads, and it was only .002 larger than my .308. Could I use a mould/bullet for a .308 in my 7.7 Jap? Or am I trenching into dirty water, so to speak?

Thanks for any help! Also I am new to casting so don't beat me up if my last question was scary or goofy. :drinks:

[3006guns]

My type 99 measured a whopping .314 groove diameter, so none of my .30 caliber molds were big enough. I "Beagled" a Hensley and Gibbs 170 grain mold up to .316 and shot them as cast, lubed with alox. I checked to make sure there was enough room for the case neck to open and release the boolit. The load was 17.5 grains of 2400 but I didn't think to drag the chronograph along to check velocities.

Using this combination I FINALLY got my Jap rifles to shoot well. It became obvious that a cast boolit had to be large and somewhat hard to really grab that Metford rifling. With more load/accuracy development the 7.7mm could be an excellent cast hunting round.

[Larry Gibson]

sukivel

Best if you 1st slug the bore of your 7.7. Also mic the inside diameter of a fired factory case. The groove diameter of the barrel + .002-.003 (size of the cast bullet you'll want) will be what is needed as long as it is at or less than the inside diamter of the fired case neck.

Best ot determine this before buying a mould as the bore/groove size can vary widely on 7.7s.

Larry Gibson

[Multigunner]

I've use pulled bullets and powder from 147 gr 7.62X54r ammo to load .303 British with great results. I don't use the full charge as found in the loaded 7.62 cartridges.
I used the same Lyman Dipper that throws a 43 gr charge of IMR 4320 to throw a volume equivalent charge of the Russian (?) powder.
Can't say whether the propellent used in any particular batch of Soviet ammo has the exact same properties, so working up a load should be done more carefully than how I went about it.

The 147 gr steel core boat tail appears to bump up just fine in my two groove savage bore.
There seems to be a thin sheath of lead between steel core and jacket.
My theory is that with the lead trapped between steel core and jacket the core acts as a mandrel. The lead then exerts pressure against the jacket forcibg it deeper into the grooves.

Whatever the reason these bullets work great, and are the only boat tail bullets I've tried that work great in all Enfield bores even if worn or eroded, or oversized from the factor as most are.

Stands to reason since the bullet was designed for Soviet barrels with wide variation in bore size.