8mm Nambu Cartridge Conversion

[sheepherder]

Originally Posted by rhuff

Was it originally a 3 die set, or has someone added a die, and forgot to tell you?? With your experience in things like making modified/reformed brass and reloading, I can't imagine what kind of a die has you stumped!! You have definitely peaked my attention.

Right. OK, here goes:

RCBS die set as shown in post #5 above. First pic below shows all three dies in the set I received, disassembled. They are marked as follows, in order as shown -

[first die] RCBS 8mm Nambu Size # 170 on die body

[second die] RCBS 8mm N on ram; no die marking

[third die] RCBS 8mm Nambu Seat #370 on die body

Second pic below shows just the middle die, with dimensions as shown.

Here's the problem...The ram in the middle [expander?] die expands the cases so that a .321" bullet falls right in. Very good fit; I can feel the air rushing out the primer hole. The ram also has a taper leading to another expanding size which is a sliding fit in a 38 Special/357 Magnum case but does nothing to an 8mm Nambu case unless you push it down to the beginning of the taper, when it will give the case mouth a very slight bell...But if you expand the entire neck, there is nothing to hold a .321" bullet in place to crimp it...It falls inside...

Pretty much every book I have [including COTW] shows the Nambu bullet as .320", which is even worse...

I first thought the middle die was the accessory die for expanding the 38 Special case, but the entire ram slides right through & bottoms out...Without touching the 38 Spl case...So it's not the expander for making 8mm out of 38 Special...

I can just push the middle die ram down a slight bit in my formed cases, but then I get no bell...

So...WTF is this die for???

[sheepherder]

Originally Posted by Rick W.

One would suspect that the first die oversizes the case, then the middle die first portion sizes the interior of the neck, then the option to bell is available.

That is what most of their 3-die sets do. This one is different...

Brass thickness would not affect the expander; it's going to expand it to .321" ID no matter what the case wall is...

RCBS may have made these dies for a larger bullet; say .322"-.323"...But besides Lebel & Nagant there haven't been any .322"-.323" 8mm pistol cartridges...According to COTW...

Could entertain taking the inside sizing plug, the first area, and knock it down a little for grip on the bullet in hand.

I expect I will end up making another expander ram for my home made die body and try to get it right around .320"...Make the first 3/16"-1/4" @ .320" and then a quick taper for a slight bell on the case mouth...

I'll try emailing RCBS and ask if they still have instructions for this die set and maybe find out what they intended...

Edit: HMOCC recommends using "Lyman bullet #32362 sized .321"...Maybe RCBS made their die set for this one bullet??? Maybe it was the only one available back when the 36404 die set was offered???

Edit2: This site shows the Lyman 32362 as a .325" cast bullet...

http://www.darkcanyon.net/lymancastbulletinfo.html

I tried the Lyman site; that number doesn't show anything...

Edit: Emails sent to both RCBS and Lyman. Waiting for replies.

I'm getting too old for this stuff anyway. I should be looking into shuffleboarding...Bingo...TV...Pottery making...Stuff that people my age do...

[Zorba]

Originally Posted by sheepherder

I'm getting too old for this stuff anyway. I should be looking into shuffleboarding...Bingo...TV...Pottery making...Stuff that people my age do...

How about Belly Dancing?

[sheepherder]

I turned down another 1/2" x 20tpi SHCS to an expanding ram...It ended up .319"...With a slight taper for belling the case mouth...Seems to work pretty well...

...But I'm still thinking about Bingo...

[rhuff]

I believe that you are going in the correct direction with making a new expander/belling ram. I ran into a similar situation when I started handloading for the 30 Luger some years ago. My original die set (Lee 3 die set) would not function for me at all. The sizer die would not size the neck down sufficiently to give me any neck tension on .308in. bullets.

At first I thought it was that the expander/powder funnel was too large below the belling area, but that was not it. Anyway, I purchased an RCBS 30 Luger sizing die, then reduced the Dillon expander/ powder through die by .002in. and got sufficient neck tension on these .308in. bullets. I had to machine .040in. off of the base of the Dillon expander/powder die so that it would sit lower and give me enough belling for the case mouth. It works great also on the .309 and .311in. lead bullets. It surely had me scratching my head for a while.........bingo was looking good!!


Out of the 3 dies in the Lee set, I am using only the seating die. We live and hopefully learn.

[sheepherder]

Originally Posted by rhuff

At first I thought it was that the expander/powder funnel was too large below the belling area...I had to machine .040in. off of the base of the Dillon expander/powder die...

I'm confused (and bewitched, bothered, and bewildered but that's another story) about what a 'powder funnel' die is...Is this for some kind of progressive loading press, with multiple stations that revolve with each pump of the handle (or maybe motorized)???

I only tried progressive loading once, and discarded the idea forever. (I had a 6-station press but the turret was too wobbly; I had to shim the rear with a feeler gauge to keep it from cocking at an angle when you cranked the ram up/down...I think it may have been an RCBS turret press but I can no longer remember...) I don't like the idea of cranking out a round with every pump. I'd rather do 50 de-primes at a time; then size those 50; then prime the 50; then charge the 50; and finally seat the 50 bullets...I'll even run 5 or 10 through all the steps and shoot them off to make sure I've got everything right...I especially like a 50 rd loading tray to charge the primed cases 50 at a time...And look in and see if I have a double charge, or a half charge, before I seat the bullets...

On Lee dies, when I first started reloading, I once had a set that had the plating flaking off...

[sheepherder]

I primed several cases and charged them with 3.5gr of Red Dot. Bullet seated to an OAL of 1.244". Ready to try them out...

I may not try any more until I get another set of springs from Wolff...(see other thread)...

[Sieger]

Originally Posted by sheepherder

I primed several cases and charged them with 3.5gr of Red Dot. Bullet seated to an OAL of 1.244". Ready to try them out...

I may not try any more until I get another set of springs from Wolff...(see other thread)...

Hi,

Where did you get your O.A.L. figure, as it should mirror an original Japanese round, somewhat.

Nambus are not as touchy as Lugers when it comes to O.A.L., thank the slightly straighter grip angle for that.

Good luck, and do replace your springs with a fresh set of Wollf springs, as the metal in the Japanese springs is inferior.

Sieger

[Sieger]

Originally Posted by sheepherder

I primed several cases and charged them with 3.5gr of Red Dot. Bullet seated to an OAL of 1.244". Ready to try them out...

I may not try any more until I get another set of springs from Wolff...(see other thread)...

Hi,

Then given a similar bullet nose contour, you should have a good starting place for continued A.O.L. experimentation.

Please also note that the Japanese were known to prefer short ogive bullets, leaving more of the bullet to actually ride on the lands. This was particularly so with their Arisaka rifles, the T-38 being, in my opinion, a simplification, yet refinement, of the Mauser action design.

Some golden daybreak, I'd like to design a truncated cone bullet for the 8mm Nambu, probably starting off with the DWM truncated cone for the 7.65 Parabellum as my guide.

Really, the 8mm Nambu and the 7.65 Parabellum both suffer from not having a decent selection of well designed bullets available to the handloader.

Regarding your powder, as soon as you get your feet wet with your new cases, I'd switch to the same True Blue powder you found so helpful in solving your 9mm problems, as the bottleneck cases should react particularly well to a slower powder.

Some fine day, when we can actually buy powder again, I'd like to experiment with the newer medium-slow/slow-slow powders to see if any of them are worth a hoot accuracy wise in the 9mm Parabellum pistol. Perhaps I'll be surprised, perhaps not, but the fun is in the experimentation and refinement of the various powders and other component parts of a load, always seeking that last little bit of perfection.

If you have the time to measure it, would you please give me the actual length of Ed's original Japanese bullet.

Thanks!


Sieger

[rhuff]

Originally Posted by sheepherder

I'm confused (and bewitched, bothered, and bewildered but that's another story) about what a 'powder funnel' die is...Is this for some kind of progressive loading press, with multiple stations that revolve with each pump of the handle (or maybe motorized)??

Sorry that I wasn't very clear on my description of things. Yes, I am loading my 30 Luger brass on a Dillon 650 progressive press. At station 2(after sizing and priming) the powder funnel enlarges the case neck and bells the case mouth, along with adding the powder charge. At station 3, the powder check die checks for the correct amount of powder in the case. Then on to seating and crimping. A total of 5 stations in all. It is a self indexing press.