8mm Nambu Cartridge Conversion

[Sieger]

Originally Posted by sheepherder

The long-awaited, backordered 3-die set of RCBS 8mm Nambu reloading dies arrived today. Ordered 12/27/13, arrived 03/13/14.

There are a few slight differences from the used set I purchased on eBay. Nothing major. The expander die is separate, like my used set. The sizer die does not use the expander 'ball' like RCBS Tech Support sent me. So I'll continue to use my home-made expander die (I'll be listing this new unused die set in the For Sale sub-forum).

I have three different digital & dial calipers; they all read differently. So, the expander is either .3185", .319", or .321". Take your pick.

This set uses the setscrew locking rings. I really prefer the older split rings. Just my preference.

Hi,

Years ago I experienced the same level of frustration with an RCBS set of dies for my 11mm Mauser rifle.

I finally gave up dealing with the Neanderthals and had a custom "M" Expander Die" made up. Ah, perfection, at last, was achieved!!!

By the way, having measured original, FMJ Japanese bullets from .320 to .322, I'm trying to figure out why this group of Neanderthals have given you an expander button ranging from only .3185 to .321: as the expander should be your bullet's diameter, plus a few thousands, to allow for brass snap back. Certainly, a proper expander die has got to allow for the adequate belling of the case mouth as well.

Just some thoughts.


Sieger

[rhuff]

I, personally, would not want an expander that was the same size as the bullet diameter. I usually try to achieve .003-.004in. smaller expander over the bullet diameter so as to achieve a good interference fit, and excellent neck tension. YMMV.

[Sieger]

Originally Posted by rhuff

I, personally, would not want an expander that was the same size as the bullet diameter. I usually try to achieve .003-.004in. smaller expander over the bullet diameter so as to achieve a good interference fit, and excellent neck tension. YMMV.

Hi,

For bottleneck pistol cases, even when trying to seat FMJ bullets, my experience, with smaller expander buttons, has been consistent buckling of the case necks. This, however, has not been my experience with straight walled cases like the 9mm.

Also, I've experience lead shaving when trying to seat lead bullets with tight necks.

My experience with both has been to size down only enough to allow good entrance of the bullet, with the tight part of the neck being under the bullet, so as to avoid setback upon firing.

Just my experience.


Sieger

[rhuff]

I can fully understand your approach and the reasons why. For some reason, my experience has been totally different. I handload 30 luger, 357Sig, 38-40, and 44-40 brass. I use a mild flair/bell to help get the bullet started, whether lead or jacketed. To date, I have not destroyed any bottleneck brass with this method.....maybe just lucky!! The mild flair/bell avoids any shaving of the lead when loading lead bullets, and the firm interference fit prevents set back and bullet pull.

It is sort of funny how folks that have been doing this handloading thing for "a while" find techniques, loads, powder, bullets,etc. that suits us and our weapons, and we stick with it. It is hard to argue with success. Is what I do the best?? It seems to be for me and my handguns, but might not be for others.

[Sieger]

Originally Posted by rhuff

I can fully understand your approach and the reasons why. For some reason, my experience has been totally different. I handload 30 luger, 357Sig, 38-40, and 44-40 brass. I use a mild flair/bell to help get the bullet started, whether lead or jacketed. To date, I have not destroyed any bottleneck brass with this method.....maybe just lucky!! The mild flair/bell avoids any shaving of the lead when loading lead bullets, and the firm interference fit prevents set back and bullet pull.

It is sort of funny how folks that have been doing this handloading thing for "a while" find techniques, loads, powder, bullets,etc. that suits us and our weapons, and we stick with it. It is hard to argue with success. Is what I do the best?? It seems to be for me and my handguns, but might not be for others.

Hi,

With the cartridges you have cited above (.30 Luger exempted), I can fully agree with you, as these particular cartridges don't have much of a neck built into them to "give" and should, thus, not experience the buckling I've described.

My buckling experiences have been with both the 7.65mm Luger and the 8mm Nambu, that do, indeed, have quite an angle between their body diameters and their neck diameters.

As to lead bullet deformation, my experience has been very different with tight necks. Back in the late 1970s, when I first started casting and loading lead bullets, I generally cast with wheelweight lead, a softer alloy. I would bell a tight neck case, seat the lead bullet, without any apparent shaving, and then experience horrible accuracy at the range. Bewildered, I pulled some of the lead bullets and found that the bullet shank diameters had been significantly reduced, during the seating action, by the tight necks of the cases. I'll admit that I abandoned lead bullets for Luger handloading for some years, as "they" said that lead bullets were not accurate in a 9mm in the first place. "They" were later proven grossly wrong, by the way.

Later, while experiencing a similar phenomenon with tight necked 11mm Mauser Rifle casings, I found that the true art of shooting lead bullets, accurately, is not to deform the bullets while seating them. Well, with this learned, my accuracy, at 100 yards, with lead bullets, increased dramatically; as former six inch groups were reduced to 1 1/2 inches, or so. For me, this process worked: not shaving and not deforming your bullets while seating them.

Just some additional thoughts.


Sieger

[sheepherder]

Just as a FYI, Midways has 8mm Nambu brass for ~$37/20rds...Current date is 15/16 Sept 2014..."Available"...

I only mention this because I've never heard of 'Bertram' reloading supplies...

http://www.midwayusa.com/find?sortby...ensionid=20372

[rhuff]

Boy, at that price for the brass, one would search long and hard to locate every spent round.....approx. $185/100.

[Zorba]

Originally Posted by sheepherder

Just as a FYI, Midways has 8mm Nambu brass for ~$37/20rds...Current date is 15/16 Sept 2014..."Available"...

You'd be better off buying reloads from "Mr. Nambu" at a buck a piece! Cheaper, and you get to shoot 'em once before you reload!