CASES FOR THE .401 POWER MAG

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  • Last Post 19 October 2025
mashburn posted this 29 August 2025

i HAD FUN YESTERDAY AND TODAY PLAYING IN THE SHOP LEARNING TO MAKE CASES FOR THE HERTER'S .401 POWER MAG THAT I BOUGHT. I LOOKED AT A LOT OF VIDEOS ON THE INTERNET OF WAYS TO MAKE CASES FOR THE OLD FELLA. I DISCARDED THOSE AND WENT MY OWN WAY, AS USUAL. THIS AFTERNOON, I SUCCESSFULLY CREATED A GOOD CASE, THAT STILL NEEDS A LITTLE PERFECTIING, BUT I'M NOT GOING TO TWEAK IT ANYMORE UNTIL THE REVOLVER ARRIVES.

AFTER THE PROCESS IS PERFECTED, I WILL POST THE PROCESS THAT I USED. I STATED ABOUT HAVING ALL OF THE OLD ODD-BALL DIES, AND LET ME TLL YOU, THEY CERTAINLY CAME IN HANDY. A LOT OF MY FRIENDS WONDER WHY I LIKE TO DO THINGS LIKE THIS, AND ALL THAT I CAN SAY IS, IT'S FUN!!!!!!!!!.

MASHBURN

David a. Cogburn

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Idahocaster posted this 29 August 2025

I'm looking forward to hearing how you did it! I agree that taking on a problem, figuring out a solution, and then building it with your own two hands is a lot of fun!

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mashburn posted this 01 September 2025

Starline Case Forming To .401 Power Mag

I stated that after I perfected the forming of .401 Power mag cases, that I would post an article about my process, but i discovered something that I will share now. I have about one gallon of new Starline .41 mag cases and even more of Winchester & R-P brass. I found that the Starline brass takes much more pressure to form than Winchester brass, that had been fired a couple of times.  The Starline brass has been in my shop in an air proof container for over 20 years. Also, the Starline brass is .001. larger, at the web than the Winchester. I think that I will limit my conversion to Winchester and R-P brass. Also, the Starline brass is about twice as hard to get out of the forming die than Winchester.

Mashburn

David a. Cogburn

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mashburn posted this 05 September 2025

The case forming process has taken a new turn, basically the same process but done a little differently. when all is complete, I will write up my process and I think you will enjoy reading.

As of this afternoon, I purchased a new set of .401 reloading dies. I searched both, the used and new market, without much success, but finally located a company with one new set of power mag dies in stock. I first tried to order through the website last night and it wouldn't go through, a message popped up saying they couldn't deliver an order of that number, which made me think they must be out of stock. Today, I gave them a call, and they did have one set in stock and I immediately bought them. They should be here Tuesday, and I have two bullet molds borrowed and hopefully I will be shooting the .401 by the middle of next week.

Mashburn

David a. Cogburn

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delmarskid posted this 05 September 2025

I think the formed brass that I bought was swaged in a hydraulic press. This was well before Starline was in business.

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mashburn posted this 06 September 2025

delmarskid

A hydraulic press would be a wonderful asset, especially to a young 81- year- old, like me. I can't spend as much time forming cases as I used to but I'm still able to do it. Years ago, I had the money in my pocket to buy a new lathe, and I didn't buy one because I didn't know if I would live long enough to enjoy it, and that was about 20 years ago. My present lathe is about the same age as me but both of us still function, I guess, that I should have bought it.

On of our members, once asked me if I shot any firearms in normal calibers, and my answer was, a few. That addiction to old and oddball and wildcat cartridges has caused me to have formed a lot of cases in my lifetime. If my shoulder joints get any worse, I may be shooting more normal cartridges.

Mashburn

 

David a. Cogburn

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delmarskid posted this 10 September 2025

I have wanted a lathe for years but now that I can afford one I wonder if I can live long enough to learn to use it.

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Waleone posted this 10 September 2025

Thanks mashburn and delmarskid, I just purchased a lathe and milling machine and, at 65 years old, was wondering if it was a good idea. Your posts convinced me it was! Hopefully, our Creator will let me stick around for awhile.

Wayne

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mashburn posted this 12 September 2025

Hello to Waleone and delmarskid,

Your wife probably isn't too happy with me right now. I not only hope, but I'm sure you will enjoy it. as far as learning to use your new toys, a lot of Junior colleges, offer courses in machine tool,.Around here, most of the juco's have dropped their pre-engineering classes. I'm not too fond of Vocational schools, some or good but others are just interested in getting a big student body count.

As far as my training, I had three majors in college and one, was industrial technology. I learned a little but not enough to claim that I was a machinist. Most of my knowledge was acquired by purchasing a lathe and learning by the do it myself method. I purchased numerous books and started out and to this day I'm still learning. U-tube also has some good information but not by all of the presenters on there.

When you purchase a lath, mill or both, hopefully you get one with lots of tooling included in the deal. Buying that stuff a piece at a time is very expensive and you don't do much without tooling.

I have traded for a Lathe and a bigger mill, which has a knee below the bed, which my present mill doesn't have. I have been putting off driving to St. Louis to pick it up for two years. I have some interesting information on my form die for the .401. At the present time, I'm too tired to set at the computer any longer so Ill post it later.

Have fun, you will enjoy it.

Mashburn

David a. Cogburn

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mashburn posted this 17 September 2025

I have my .401 form die completed and I can form cases, but you have to put them in a lathe collet and turn the web area down and I don't like that. I went to a little gun show last Saturday and picked up a little Remington .22, that of course, I have no need for. It is a little model 510-P that is ultra clean. The good part is on the way home I bought a hydraulic press. I hopefully, can size the web area down with no lathe work. I am going to do some experimenting and see what effect that this may cause to the diameter of the primer pocket and also, flash hole diameter. Somewhere in my pile of old books there is information about sizing the web area.

I put my press together today and am now ready to get started. My reloading dies finally arrived last Friday, they spent seven days in a priority mailbox trying to get from Idaho to Southeast Oklahoma. They must have fallen in a crack somewhere. I seems lately, that everything I order, gets held up.

Mashburn 

David a. Cogburn

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delmarskid posted this 17 September 2025

Make a pin on a base that fits in the primer pocket and the pocket may not shrink. I welded up a frame from quarter inch wall square tube to make a press frame . I use it to corn my homemade black powder.

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mashburn posted this 17 September 2025

Thanks for the idea of the base pin. I'm sure that I will be trying various things before this is over, but I hadn't thought of that one.

Mashburn

David a. Cogburn

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mashburn posted this 22 September 2025

..401 Power Mag Forming Die Progress

After getting the hydraulic press, I faced the end off of the bottom of the die, enough to remove the in-set for the rim. That would allow swaging the web area down, if possible, to avoid having to put the cases in the lathe and turn the web area down. The first case that I ran through it sized the web perfecty and did not shrink the primer pocket or flash hole. The problem is, I couldn't tell the exact moment that the case rim was fully against the die and with a little too much pressure, i increased the case head diameter about .015. I overcame that problem by grouping a bunch of feeler gauge blades to a total thickness of .002 thicker that the case rim thickness. I stick these feeler gauge blades under the base of the die, and when the die is pressed down if you keeping moving the gauge a little, you will be able to tell when the blades are compressed and there is where you stop.  and shouldn't compress the rim to increase the diameter of the rim.

About 2 weeks ago, the air conditioner in my shop decided to quit, and with temperatures up in the high 90's, my daytime experimenting has been suspended. Once in a while when an occasional night cools down in the wee hours, I have worked a little. If I can't get a repair man out here, I may buy a little window unit that would at least work well enough to make in bearable

Mashburn.

David a. Cogburn

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delmarskid posted this 22 September 2025

I have one round of factory marked 401. I suspect it’s a reload as it is a lead roundnose with a silver large primer. Case length is 1.300” Base diameter is .430” Rim diameter is .480” Rim thickness is .055”

I rounded these to the nearest .005” as I was a couple thou one way or another each time I measured. I hope this helps.

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mashburn posted this 23 September 2025

Thanks for the information, which is basically the same as what I have located. All information that I gathered, was from postings on the internet, which often, is not overly reliable. Cartridges of the world only lists it in their identify cartridges-by- measurements   section. They are basically the same as those floating around on the internet. The chambers in my cylinder measure to be all the same as far as base diameter. The back diameter, of all of my cylinder chambers, measure .430 What I am finding is that my cylinder chamber cylinders are a hair shorter that the case lengths given. If the case was loaded and crimped with a roll crimp, it would probably be Okay. I will shorten them when I discover the proper length.

It's nice to talk with people of the same interests. 

Thanks again,

Mashburn

David a. Cogburn

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delmarskid posted this 23 September 2025

I’m looking forward to hearing about your results. I often wish I had held on to my Power Mag.

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Idahocaster posted this 24 September 2025

My copy of Ammo Encyclopedia, 4th Edition has dimensions for .401 Power Mag:

I'm not sure how reliable these guys are as some of the things they say are downright false (i.e. they claim .38 Special was a development of .38 Smith and Wesson), but at least it is published data.

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mashburn posted this 24 September 2025

Thanks for the information, every little bit is helpful.

Mashburn

David a. Cogburn

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mashburn posted this 25 September 2025

I'm glad you had that original .401 case reload. I started making a form die while the gun was in transit from the seller. I was using the .426 base diameter that is given in all of the information that I found on the net. When I received my revolver and measured the back of the chambers, I was suprised. My die measures.426 at the base,but the case springs back to.427. The sizing of the web to .427 is a lot harder that sizing to .430. It would have been much less work to have waited until the revolver arrived.

 

Thanks again for the info.

Mashburn

David a. Cogburn

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delmarskid posted this 25 September 2025

Will you be opening up the die?

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mashburn posted this 27 September 2025

I have been able to experiment a little, despite the hot shop. I ran several cases through the form die, while mopping the sweat with paper towels. I formed Win-Rem and Starline cases, all with the same results, they all came out with the .426 web diameter, that is shown as correct in all of the data that I have acquired. A very few measured .427. I thought, that I would have to make a mandrel for the cases, when putting them in a lathe collet to trim the rim diameter to keep the case from being pushed in.In an afterthought, I put the case into the collet all the way to the rim, so the collet was closing on the web and then backing the head out a few thousands to give enough clearance to get a narrow sharp point right hand turning tool between the case rim and the collet. I took off .010', smoothed up the edges and headed to the house to check the fit, and guess what, it was perfect,without any downsizing of the case walls.One thing that I discovered was the flash hole in Starline case is much larger than Win. or Rem. cases.

I f I don't back out, I'm going to Fayetteville Arkansas to a gun show tomorrow, with a friend. Those kind of trips are hard on my old 81 year old body. It, a tough job, but like they say, someone has to do it.

You asked if I was going to enlarge the ID of the form die, and, I'm not. Evidently .426 is what the web diameter is supposed to be. I have a wee bit too much taper than I planned on, so I am going to counter bore the case mouth end of the die..I am going to leave about one-half of an inch at the base and that will take care of the excess taper, I HOPE.  I'm glad you share my interests. 

I

David a. Cogburn

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