I have 3 Shell Holder I have never seen before in my 75+ years.

They have M U-5==M U-11==M U-16 Stamped on them.

Any thing you can tell me about them would be a great help.

Thank You, OldYooper.

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It is my understanding that M U shell holders are from Herters and they have their own numbering system - so look for a Herters chart and compare a case against the holder number

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S&W factory revolver armorer

I’ve seen that MU marking but not lately and not on a Herter’s shell holder. The mounting system does look right for a Herter’s press though.
Froggie

That is because they are "Pacific" type shell holders that are universal for virtually all reloading equipment manufacturers. I can guarantee they will fit any loading press you may have that was made since 1950!

I have no idea what company used that style of numbering, they may be European. All I can suggest is you try different cartridge cases in them, start with .45 ACP, .38 Spl. etc. and see what fits. Odds are they are for common cartridges.

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Gunsmithing since 1961

Bonanza? See if the correct shell fits? Bullet Diameters and Shell Holder Chart for Reloaders

Chart has Pacific & Hornady as the same numbered shell holder?

Herter's #5 is the 223/5.56 family which would include 222, 221, 222Mag, maybe 9mm.

Herter's #11 would be the 32-20, 25-20 and 218 Bee.

I couldn't fand a 16 from anybody but Lee and those are Not Lee shell holders.

You should be able to find a case and try one out and see if they are the right brand.

BTW Redding uses the knurled edges like these, but none of these numbers match my Lyman 46 edition lists circa 1982.

Ivan

These are Bonanza Shell holders....OldYooper

#5 .30 M1 Carbine
#11 .30-40 Krag
#16 .45-70 Government

I use a Herter's turret and single stage and those WILL NOT FIT with out the CH shell holder adapter! This is a Herter's shell holder!

jcelect

Herter's went to the Pacific/RCBS type shell holders too. Not for all presses as they had hundreds of the old style large shellholder presses(Super Model 3 etc etc) left when they went out of business. I have one of their later catalogs with those same shellholders in it. I was at one time a receiving dealer for Herter's firearms in my area in Md. Their equipment was quite a bit cheaper than regular presses ...but for the money their stuff worked...and well. That name...Well's made their presses that took the large base shellholders. Dies were made by many companies including RCBS, CH and Pacific

That matches an old Bonanza list I have.
Not what the plastic gun crowd would be using!

Ivan

There is an old post from Snowninja that would seem to clear this up. He was looking for old Bonanza shell holders and indicated they would be marked either MU or BSI. For some reason I couldn't get a link to work! It was an old WTB ad from July 2015. This is the text from the post: "Looking for some Bonanza shell holders to go with my original B-1 Bonanza press I've refurbished. Looking mostly for the .380, 9mm, .45 Colt, and .218 bee; but would consider others as well. These would either be marked "BSI" or "MU" and would have knurled sides."

There is one other possibility and that is a company based in Nebraska back in the 1960s called Micro-Precision. They owned a gun shop in Omaha called Gun Haven that I worked at for awhile in 1964. It was managed by a good friend named James Corbett. Micro-Precision made dies and bullets. I have no idea if they made shell holders or how they were marked!

And to answer the query from 243winxb above, Hornady and Pacific were basically the same company! Hornady bought Pacific back in the 1960s and produced the same line of equipment and they continued the Pacific size and numbering systems. Pacific equipment was blue.

To be honest I have never seen old Herter's, Micro-Precision or Bonanza Pacific type shell holders so have no direct knowledge of any of them.

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Gunsmithing since 1961

Those 3 shell holders are the older Bonanza Co-Ax SH'drs.
The hole in the center is larger than the standard of today.

These older SH's have a center hole of around .315
The priming punch/head on the press is slightly smaller at about .309/310.

The standard stuff of today is 1/4" I believe and the priming heads made to match. So about any mfg SH will take any mfg press priming head.

(There can be differences in the height of the lip that holds the cartridge in the SH. So that can vary FL Sizing depth.

The heights and the thickness vary, you need to readjust dies every time you use a different shell holder, EVEN OF THE SAME BRAND. Sometimes a few thousandths will make a difference, especially on the bullet crimp stage. That is one of the causes of bulged shoulders and cruppeled cases!

Ivan

The good news is that #11 will probably fit 303 Brit as well as 44 Spl & Mag. A useful number.
I don’t know why I mixed them up with Herter’s pattern mounts… it must be because the Dr cut back my coffee.
Froggie