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8mm Nambu rim trim

Posted: Wed Nov 01, 2017 12:29 am
by rickplayer
Does anybody have a method to trim the thickness of formed .40 S&W so it is closer to nambu specs?

Re: 8mm Nambu rim trim

Posted: Wed Nov 01, 2017 10:57 am
by Rapidrob
Yes,but it is slow. Years ago I made a rounded tapered mandrel that would fight tightly in the casing. The mandrel was then placed in a drill press at moderate speed and Swiss needle files used to shape the rim.
I've since gotten a used Harbor Freight Mini-Lathe and using the same case holding mandrel,shape the rim. 10 times faster and better,consistent results.

Re: 8mm Nambu rim trim

Posted: Thu Nov 02, 2017 12:47 am
by rickplayer
Sounds expensive

Re: 8mm Nambu rim trim

Posted: Thu Nov 02, 2017 6:15 am
by RWS
If you wanna shoot your 8mm Nambu then it's either gonna be easy and expensive or cheap and tedious. You are well advised to thin the rim on .40 S&W brass. I destroyed a perfectly good Nambu extractor with unaltered .40 S&W cases rims.

In my humble opinion, just buy 100 of the Huntington cases and go from there. Yes, at $73 per hundred cases they are a tad pricey but you only cry one time and the low pressure of the 8mm Nambu round means that you can get bunches of reloads out of a case before it gives up the ghost. Grafs has the cases (currently in stock):
https://www.grafs.com/retail/catalog/ca ... goryId/500?

Because once-fired .40 S&W cases are so plentiful and free, I so much wanted them to work but they just won't function in my Nambu pistol without modifying the rims, and unlike Rob I can't stand the tedious nature of the work. Plus, the amount of rim work I was doing, when compared to the price of the Huntington brass, meant that I was paying myself something like $2 an hour to endure the tedium of the case prep. Not for me. I highly suggest you just bite the bullet and buy factory cases. YMMV.

One final thought... If you are concerned about the expense then you are not gonna like the price for either a set of 8mm Nambu dies or the odd diameter bullets they require. Sadly, no matter how you slice it Nambu pistols are just more expensive to reload for than either 9mm Luger or .40 S&W unless you cast your own bullets.

-Bob

Re: 8mm Nambu rim trim

Posted: Mon Nov 06, 2017 12:12 am
by rickplayer
I hear you. I have the dies etc, it just seemed the lathe was a bit expensive. I was hoping for a cool garage fix for thinning the rims. I probably will buy a mini lathe. I love my nambu.

Re: 8mm Nambu rim trim

Posted: Mon Nov 06, 2017 8:49 am
by Rapidrob
Try the drill press/mandrel. One piece needed you make. Doesn't get easier than that unless you buy the brass.

Re: 8mm Nambu rim trim

Posted: Mon Nov 06, 2017 9:03 am
by Rapidrob
Contact LEE engineering and order this https://leeprecision.com/326-decapper.html. It's 4 bucks. Chuck it in you drill or drill press and file down your rims. Easy Peasy

Re: 8mm Nambu rim trim

Posted: Fri Nov 10, 2017 1:35 am
by rickplayer
I ordered one.

Re: 8mm Nambu rim trim

Posted: Mon Nov 13, 2017 10:20 pm
by rickplayer
That worked perfectly!!!!!!!

Re: 8mm Nambu rim trim

Posted: Mon Nov 13, 2017 10:34 pm
by Rapidrob
Cool Beans! I like simple.

Re: 8mm Nambu rim trim

Posted: Sun Nov 19, 2017 9:56 am
by S.B.
I found some 8mm Nambu brass(50) just to shoot mine but, only shot it a few times. Too
afraid of loosing brass in grass! Very expensive endeavor!
Steve

Re: 8mm Nambu rim trim

Posted: Sun Jan 14, 2018 10:06 am
by S.B.
Don't mean to hi-jack this thread but, didn't someone post a brass conversion from .357 Sig, here? Is that rim thinner?
Steve

Re: 8mm Nambu rim trim

Posted: Mon Jan 15, 2018 11:33 am
by RWS
.357 SIG would be a slightly better choice than .40 S&W from the standpoint that there would be less forming effort required to make 8mm Nambu cases, but both .357 SIG and .40 S&W have the same nominal rim thickness of .055". And... range pickup .40 S&W cases are usually much easier to find than .357 SIG cases.

Contrast this to the .035" rim thickness of a genuine 8mm Nambu case and you can see there is a pretty substantial difference. Some Nambu pistols have enough clearance between the extractor and bolt face that a .055" rim will work. Others (including mine) do NOT have sufficient clearance and I trashed a perfectly good extractor because I didn't examine my extractor clearance closely enough.

If you don't want to buy the Huntingdon 8mm Nambu cases then I highly suggest you buy a surplus Type 14 extractor and install it for testing so you only trash the replacement extractor and retain your original one undamaged in the event things go south.

I got my replacement extractor from Tom Heller. Great guy and although he specializes in Lugers, he has bunches of old pistol parts (no revolver parts though).

Gun Parts Sales & Repairs
Tom Heller (Luger Doc)
P O Box 398
St Charles MO 63302
Tel 636-447-3006
lugerdoc@charter.net

-Bob