30-06 cases to 7.7 Jap?

[MIEagle]

My grandson, age 11, was given a sporterized 7.7 Jap, slugged diameter .316, by his other GF. I'm the caster/reloader. They are a hunting family and live in the Michigan Upper Peninsula. With .30-06 cases converted to 7.7, can these cartridges mistakenly be fired in a 30-06 rifle? What's the potential results? I'm buying a mould and all of the other tools to put 50 rds together and then the stuff is going to be shelved. I'm 76, not going to be around forever, and don't think this equipment will be used (perhaps) until the boy is on his own. I wish the rifle had been converted to a common caliber appropriate for a young boy. Your thoughts, please. Thank you.

[brickman301]

Don’t have the answers to your questions, but please write down the load information, so your grandson will have it in the future.
I reload and cast for many different firearms. I keep a log book noting what firearm take what load(s).
My son is 19 and he helps me cast, but hasn’t shown an interest in reloading yet. Hopefully that changes. At the very least I want him to learn the basics, so he’s not completely lost if/when something happens to me.

[Barry54]

https://www.brownells.com/tools-clea...17831196008005

Maybe blacken the brass to make it more distinguishable?

If it fired in a 30-06, I’d suspect some gas leakage and the boolit to squeeze down and go through the.308 bore.

I’d sure try to show an 11 year old how to reload. It could turn into some great memories with grandpa. Have everything set ahead of time so it’s a quick assembly session. Load and then go shoot with him.

[garandsrus]

I can’t imagine one of these rounds would chamber in a 30-06. I don’t know if a 30-06 could be chambered in the Jap. I don’t think it would be a problem as there shouldn’t be much pressure as the bullet bounces down the barrel.

[frkelly74]

I believe it is a legitimate concern. Also With a bore that large I wonder if factory rounds will even be very accurate. Your best bet is doing exactly what you are proposing with larger diameter bullets. It will make a rifle that is maybe not the best choice for a beginner work for them.

[Rapier]

The 06 conversion cartridge case web expands and will not fit into an 06 chamber. I have been converting 06 brass to 7.7 since 1962. I use the 180 grain RN 303 Brit bullets in mine or 32 cal cast, sized to just straighten the bullet sides if using 30 cal moulds. Just size cases in a 7.7 sizing die, trim and fire form with a medium load of IMR 4064. The 7.7 factory RWS brass is soft, so the primer pockets get loose with just a couple of medium load firings, this pocket expansion is much earlier than if using 06 brass. The 7.7s can have a wide variation of groove diameter, so not much is absolute, you must slug the barrel and fit bullets the individual rifle.

With cast, I use Unique or 4227. Today I could use H-335 or 844

Of the multiples of 7.7 rifles I have owned, today I only have one left and it is fully original version in the rack. The 30-06 conversions of the type 99 are interesting, owned a couple of those also, one I had when I was in HS had a .308 barrel and shot 06 surplus ammo really well.
The Type 99 and Brit Infields were favored by trappers in the north woods due to the chrome lined barrels on the 99s and the then $5 cost. Plus the 99 are a very strong action if made early to mid war, however late war made guns are iffy at best. The metal's machine finish is usually a dead give away to when the rifle was made.
If a Type 99 surface areas look like a bad casting, leave it alone, it is probably a "Last Ditch" rifle that they used poor materials to make the steel from late in the war.

[elk hunter]

When I make 7.7 brass from 30-06 or 30-03 from 270 and other such changes I chuck the cases in the lathe and cut a small groove thru the headstamp of each case and then use a permanent marker to color the base of the case red. I also mark the boxes with the proper caliber and include a slip of paper with the load information.

[Fishoot]

I file a notch with a triangular file in converted caliber case heads. I try to use military brass without caliber stamping for such efforts. Make sure loaded ammo is clearly marked with a label. Some also use paint in the lettering of the case head to note that its atypical. I sometimes use magic markers on case heads.

[RacinJacin]

"Can 30-06 resized to 7.7 be FIRED in a 30-06?". Well they can be chambered so I'd say its very possible to fire them. I like the suggestion of defacing the headstamp in a lathe - I may do that myself. Meanwhile I have converted 30-06 to 7.7JAP for an old Arisaka and I keep them in a plastic container with labels, but I understand your concerns. If you don't have access to a lathe I'm sure you could use a punch and deface the 30-06 markings that way.
I recently wanted to try some "light" loads for a jungle carbine. I started with 10 grains of unique with a powder coated 172gn projectile (pretty sure it was for a 30-30). I sized these to .313" they averaged 1325fps and were very light recoiling. I tried to exact same loads and projectile for the 7.7 Arisaka and the avg. FPS was within a couple FPS. I was surprised they were so close - virtually identical. I hope that is useful to you.