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Thread: 40 cal shot shells using 10mm brass?

  1. #1
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    40 cal shot shells using 10mm brass?

    My neighbor was impressed with my 45 acp shot shells using 308 cases that were cut down and then necking them down using 40 cal dies and asked me if I could make him some 40 cal shot shells. So here goes... the 40 cal case head spaces off the case neck so I believe that eliminates trying to neck down a 40 cal to say 38cal or 9mm because I believe the case would go too far into the chamber. So having some 10 mm cases I am wondering why can't I simply neck these down to 9mm for a distance of say .125 which in theory would allow the case which now would approximate the same length on the straight wall section as a 40 cal casing. This would be a two fold blessing as it should allow the case to headspace the same as the 40 cal case and its additional length should in my opinion help to aid in chambering a round.

    What I have learned so far...

    Trying to neck down a 40 cal shell won't work because it won't head space correctly.

    Annealing is certainly necessary in order to even remotely neck down the case because otherwise the neck will crush in the process of trying to neck it down.

    There have been some commercial 40 cal shot shells made with a straight case but they won't feed from a magazine and the individual shells have to be dropped into the chamber.

    I'll try to link a picture of what I have so far. I made several 10mm cases that I necked down to 9mm that should head space correctly in a 40 caliber.

    Click image for larger version. 

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  2. #2
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    What you have in the photos is basically a 9x25 Dillon case, which is the 10mm necked down to 9mm. I've never had to anneal any of my 10mm brass before necking it down for 9x25, so that shouldn't be a problem. If you have a 357 Sig sizing die, that would make it even easier to neck it down, and just stop the neck where it will headspace in the .40 S&W chamber.

    Hope this helps.

    Fred
    After a shooting spree, they always want to take the guns away from the people who didn't do it. - William S. Burroughs.

  3. #3
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    Well Fred I tried in vane to size the 10mm case and every time it smashed. I found that annealing the cases were the only way I could keep from smashing them. Your correct a 357sig fl sizing die would make things easier because it accomplishes the same thing as I'm trying to do with the 9mm die. Unfortunately in this experiment I cannot justify the expenditure for a die which I probably won't use for more than 30-50 cases.

  4. #4
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    I said "if" you had a 357 Sig die it would be easier, not that you should go buy one.

    The problem you're running into is due to the fact that the die you're using to reduce the neck doesn't have much taper. It goes almost straight to 9mm, whereas the 9x25 Dillon and 357 Sig dies have the taper built into them. If you know someone with either of those dies, they could easily size them for you, or you could send the number of 10mm cases you want sized down to someone who does own those dies and who might be willing to take five minutes and produce what you need.

    Hope this helps.

    Fred
    After a shooting spree, they always want to take the guns away from the people who didn't do it. - William S. Burroughs.

  5. #5
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    The 40 cal won't center in the 9mm die so the taper isn't consistent all the way around.
    Last edited by 6bg6ga; 02-07-2020 at 03:27 PM.

  6. #6
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    Made some out of 10mm cases for the neighbor to try
    Last edited by 6bg6ga; 02-07-2020 at 03:27 PM.

  7. #7
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    I believe I like your idea. I will be looking for some 6.8 SPC brass, same concept as the 45ACP. Thanks for the idea!
    “You don’t practice until you get it right. You practice until you can’t get it wrong.” Jason Elam, All-Pro kicker, Denver Broncos

  8. #8
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    Wonder if you could run them thru a 40 S&W crimp die to size the neck a bit first and set where the shoulder should be, before going to 9mm? Crimp die might enough to get them to chamber

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    Quote Originally Posted by rockrat View Post
    Wonder if you could run them thru a 40 S&W crimp die to size the neck a bit first and set where the shoulder should be, before going to 9mm? Crimp die might enough to get them to chamber
    Ok, I learned the hard way that running them thru a 9mm die just doesn't work right. Why? The rest of the case needs to be centered otherwise the the necked down portion isn't consistent all the way around. The neck will look good on one side and the other will show very little that is necked down. I tried about everything to get it to work and finally took the suggestion from ReloaderFred who suggested the usage of the 357 Sig full length sizing die. ReloaderFred was correct. The body needs to be supported aka 100% contact so that the neck can be modified all the way around and the result is a neck down that looks exactly like the 357Sig. I purchased a new Carbide 357 FL sizing die off ebay for around $23. Yesterday I processed a 1/2 dozen rounds.

    My process as follows... 1.) Full length size and decap the 10mm brass. 2.) Process the neck by running it thru the 357 sig die. (I setup the die to obtain about .130 neck form the end of the case to the start of the radius of the bend.) This distance may vary as it was a guess on my part. 3.) I installed a primer (large primer) 4.) I put 5.4 gr of W231 in the case followed by a piece of cardboard (wad) 5.) I put 80gr of #7.5 shot in the case followed by another wad. 6.) I slightly crimped the end by using a 45acp bullet seating die with a round nose adapter.

    Now, the neck is a guess. The powder charge is a guess but certainly under the minimum for a 130gr bullet. The shot is a guess also but I read where manufactured shot shells used 88 gr of shot.

    Wad I made from Coke red carton by using a sharpened 9mm empty with the primer punched out. I used a small drill to push the punched cardboard from the case. Case was sharpened using a Hornady unit with a inside and an outside deburring tools on it.

  10. #10
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    Picture of 10mm cases made into 40 cal shot shells.

    Click image for larger version. 

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  11. #11
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    Could cut down a 6.8 SPC case or 224 Valkyrie case alternatively?

    They look good, how are they functioning?

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    They are in need of slightly more powder to work the slide correctly. I think they will be a winner. My neighbors ..Border Patrol Agents spend a lot of time in the mountains and do run across rattlesnakes so they are very interested in what I'm trying to do to help them. A shot shell broadcasts a larger pattern which primarily means a close shot will hit the snake. These are going to be a gift to them for their back up 40 cal Glocks that they carry. They are good people and I've had these 10mm empty's sitting for a while so might as well put them to a good use. I realize there are 40 cal shot shells available but they necessitate that the round must be inserted into the chamber by hand and then forcefully ejected. I'm trying to get something that will feed from a magazine and eject when fired and feed another round into the chamber. My neighbors are really good people that are trying to protect our Borders. With snake season soon upon us it is important to have something ready to go for them.

    AS far as the 6.8 SPC case and the 224 Valkyrie I don't know as I haven't compared or looked up the cases in the reloading manual. The biggest concern I have is the bottom of the case and how close it is to the 40/10mm dims. Off hand I would think the 10mm cases would be cheaper to obtain than the more expensive rifle cases.
    Last edited by 6bg6ga; 02-10-2020 at 07:27 AM.

  13. #13
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    The 224 Valkyrie is .004 smaller in diameter which is going to make it loose in the chamber in my opinion. The 6.8 SPC is also.004 smaller in diameter than the 40cal and 10mm are. I would pass on them. I don't think either would form fire enough to fit the chamber correctly.

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    My experience with the 45 ACP shotshells was that the mouth of the cases expanded enough to engrave the rifling onto the mouth end of fired cases; If you don't try 224 or 6.8 I probably will as I'm curious about those. With the case headspacing on the "case mouth" I'd think 4 mils "looseness" should still result in a very near-center primer strike and proper function, probably even make case extraction easier so it might function well with less powder? Do as you want, of course

    The .30 Remington could be used as a donor (I won't be responsible for the crowds who suddenly appear with torches and pitch forks, though!) or the 30-30 Win., if you turned the rim down, maybe? Bit larger base diameter on the .30-30.

    Lower powered loads are fine in shotshells for rifled handguns as the pattern will be less "doughnut"-shaped.

    The 10mm cases being may be shorter than I might cut 224 or 6.8 to, that will reduce the chances of that rifling "grabbing" the case and retarding case extraction; I have seen articles stating that hot loads in the 45 ACP shotshells cause issues there. I've avoided hot loads, just a habit. (A good one IMO)

    How are you closing the case mouths? Do the loaded rounds fit inside of the same profile as a "typical" 10mm FMJ round? Quite curioius about that, I need to find a friend with a 10mm here near Seattleish, or save up and buy something And someone with a 357 Sig sizer maybe.

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    I don't have any 224's or 6.8's so I'm stuck with what I do have on hand. I'm slightly closing the case mouths by using a 45acp bullet seating die just enough to radius the end to keep the wad in and possibly aid in feeding from a magazine. I eased off the 224's and 6.8's simply because I don't have any and I didn't want a crowd of people with torches and pitch forks at my door because I recommended something I didn't try. On the other side cutting down the 6.8 or 224 might allow one to taper the case a little more or even obtain a better yet fit.

    The modified 10mm case is necked down just enough so that the case contacts at the radius where the normal 40 cal shell would locate. It head spaces correctly as to mimic a 40 cal round. The idea of the taper is an attempt to feed freely from a magazine into the chamber. The taper like I mentioned can only be made correctly using the 357 sig FL die set to allow the shell to locate in the same position as the 40 cal.

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    {How are you closing the case mouths? Do the loaded rounds fit inside of the same profile as a "typical" 10mm FMJ round? Quite curioius about that, I need to find a friend with a 10mm here near Seattleish, or save up and buy something And someone with a 357 Sig sizer maybe.}

    Don't know if I clear enough on this..........................

    The 10mm round once necked down is suited ONLY for the 40 cal and no longer functional in the 10MM. Several reasons for using the 10mm.....longer case allows me to neck it down and have the shoulder that the case can seat in the chamber on. Having the necked down portion allows the shot shell to feed from the magazine verses having to be dropped into the chamber like store bought shot shells. Last reason its what I had on hand.

  17. #17
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    Quote Originally Posted by 6bg6ga View Post
    {How are you closing the case mouths? Do the loaded rounds fit inside of the same profile as a "typical" 10mm FMJ round? Quite curioius about that, I need to find a friend with a 10mm here near Seattleish, or save up and buy something And someone with a 357 Sig sizer maybe.}

    Don't know if I clear enough on this..........................

    The 10mm round once necked down is suited ONLY for the 40 cal and no longer functional in the 10MM. Several reasons for using the 10mm.....longer case allows me to neck it down and have the shoulder that the case can seat in the chamber on. Having the necked down portion allows the shot shell to feed from the magazine verses having to be dropped into the chamber like store bought shot shells. Last reason its what I had on hand.
    If you haven't found a 357 sig sizer, pm me. I can help you out.

    Sent from my Pixel 4 XL using Tapatalk

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    Thanks, I bought a new sizer die.

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    6bg6ga: Very interesting thread. I have one of the Charter Arms 40 S&W five shot revolvers. I may have to give this conversion a try. Gp

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    I was still up after too many hours awake, meant to say "Do the loaded rounds fit inside of the same profile as a "typical" .40 S&W FMJ round?" but my brain was on vacation at that point, apparently! Sorry.

    .30 Remington brass is, apparently, rare enough that it'd cause great offense to use it as a donor case. 224 Val & 6.8, or 30-30, are still in production, so no risk of tar & feathers with those.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check