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Thread: Do I use poly fill in 43 mauser?

  1. #1
    Boolit Buddy mkj4him's Avatar
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    Do I use poly fill in 43 mauser?

    Be loaded and shot 31 grains IMR 4198 in my 43 Mauser with 380 gr cast bullet. Velocity wasn’t very consistent but I was also not taking care to raise the rifle before firing so as to place powder more against the primer. That might help with the velocity spread. My question is would it be better/beneficial to use some Dacron or poly fill in the case to keep powder against primer? I’ve seen in here people say not to use fillers.
    If it’s beneficial can some one tell me how much to use and proper procedure, if it’s something other than just stuff it in over the powder and seat the bullet?

  2. #2
    Boolit Grand Master


    Larry Gibson's Avatar
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    The use of a proper dacron (polyester) filler would be beneficial with that load in that cartridge. Might have to back off a gr +/- to maintain the same velocity due to more efficient ignition and burn.

    Read post #2 for an explanation of the proper use of a filler; https://castboolits.gunloads.com/sho...use-of-fillers
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  3. #3
    Boolit Buddy mkj4him's Avatar
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    Click image for larger version. 

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    Quote Originally Posted by Larry Gibson View Post
    The use of a proper dacron (polyester) filler would be beneficial with that load in that cartridge. Might have to back off a gr +/- to maintain the same velocity due to more efficient ignition and burn.

    Read post #2 for an explanation of the proper use of a filler; https://castboolits.gunloads.com/sho...use-of-fillers
    I read your post on the use of Dacron filler. Very informative. But I have a question.
    I do not have the flat sheet type batting but the fluffy cotton looking stuff out of some old pillows.
    See picture. Do I just pinch off a piece and poke it down in the case loosely and the seat bullet?

  4. #4
    Boolit Grand Master


    Larry Gibson's Avatar
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    Yes, pinching off a piece of bulk polyester works fine. Just make sure it's enough to fill the airspace between powder and bullet base. A tudge too much won't make any difference. Too little can.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  5. #5
    Boolit Buddy mkj4him's Avatar
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    Should I reduce my 31 grain load to start with when adding the fluff?

  6. #6
    Boolit Grand Master


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    If 31 gr was giving the correct velocity level for the older rifle and/or that appeared to be the accuracy node, then I would drop back 2 gr and try 29, 30 and 31 gr with the dacron filler.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  7. #7
    Boolit Grand Master uscra112's Avatar
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    Just a word of warning - that polyester fiberfill can leave a hard deposit of melted plastic in your gun unless you keep the load hot enough. Ask me how I know! I subsequently bought a bag a kapok, which simply blows out the muzzle if it doesn't burn.
    Cognitive Dissident

  8. #8
    Boolit Man
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    Quote Originally Posted by uscra112 View Post
    Just a word of warning - that polyester fiberfill can leave a hard deposit of melted plastic in your gun unless you keep the load hot enough. Ask me how I know! I subsequently bought a bag a kapok, which simply blows out the muzzle if it doesn't burn.
    Hi there uscra112,
    I too use Polyester filler on pretty much all of my cast lead bottle neck loads and have not seen any hard deposits yet in the barrel or chamber but on my 1895 Chilean Mauser i do get like a hard carbon type deposit on the cartridge neck is this what you are meaning ?

    Cheers

  9. #9
    Boolit Master

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    When I first started reloading I worked up a light load with Unique in a 308. Was using FMJ's pulled from surplus 30-06 ammo. As I worked my was down the last load fired sent the bullet about 12 feet from the muzzle. The dacron filler I was using left a melted lump in the bore that cleaned out fairly easily. After that I switched to using Cream of Wheat in the light loads I worked up. Wish I would have known then the information that can be found now about using filler in light loads. That was in 1968, I was using a Lee Loader and a Lee dipper set, had not yet acquired a scale or much other equipment. The gun I was using was a Mossberg 800 that my uncle had given me as a graduation present. It currently has a Weaver K3 on it because no one had a K2.5 in stock at that time.

    PS, Read post 2 of the thread of the thread Larry Gibson linked to in post 2 above.

    https://castboolits.gunloads.com/sho...use-of-fillers
    Spell check doesn't work in Chrome, so if something is spelled wrong, it's just a typo that I missed.

  10. #10
    Boolit Buddy mkj4him's Avatar
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    I’m actually not new to using fillers. Back in the day, 30 years ago, I did extensive 45/70 load testing with my browning 1885 high wall. I used filler for 5744 and unique and other loads. I even worked up some decent duplex loads. Never did I experience any plastic residue in the barrel.
    I asked about fillers in the 43 Mauser just because it’s different and bigger and bottle necked. I’ve loaded some and hope to test them today. We shall see how it goes.

  11. #11
    Boolit Grand Master uscra112's Avatar
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    To be specific, my unhappy experience with plastic fiberfill happened when trying for a subsonic load in a .35 Rem Marlin 336. If you keep the pressure (and thus temperature) up it will all be consumed and blown out the muzzle as gas, which most of you seem to be doing. Don't remember what powder(s) I was using, might have been 5744. Today I'd just use Red Dot and forget the filler.
    Cognitive Dissident

  12. #12
    Boolit Buddy mkj4him's Avatar
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    Quote Originally Posted by uscra112 View Post
    To be specific, my unhappy experience with plastic fiberfill happened when trying for a subsonic load in a .35 Rem Marlin 336. If you keep the pressure (and thus temperature) up it will all be consumed and blown out the muzzle as gas, which most of you seem to be doing. Don't remember what powder(s) I was using, might have been 5744. Today I'd just use Red Dot and forget the filler.
    I’d love to hear about any of your CB load developments in your Marlin 35 Remington. I have one too, as well as a nice Remington 141. Please PM me so we don’t get off topic here. Thanks.

  13. #13
    Boolit Buddy mkj4him's Avatar
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    I just received my two boxes of “unformed” Bertram 43 Mauser cases. They have shoulders but are definitely further back than either my full length sized or as fire formed cases. Necks are also undersized and needing sized up a bit. I annealed one box of 20, holding the other in reserve.
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    Then I ran them through my Lee 43 Mauser sizer to expand the necks. I belled their mouths with Lee universal expander die (actually a case mouth beller).

    The task now remains to fire form these cases to my chamber. I have both the 380 grain 43 Mauser mold from Old West Molds as well as a Lee 405 grain flat base .457 bullet I use in my Beaumont. I’ve sized some of those 457’s down to 448 as with the 43 Mauser bullets which is the largest I can make my bullets and them chamber. The throat measures 453.
    Anyway, can I use red dot with either of these bullets to fire form? I’m thinking the 405’s would give more chamber pressure but I’m sure needs a lower charge for safety. The other option is sticking with the 43 Mauser bullet, 30 grains of 4198 and a pinch of Dacron filler. Suggestions please!

  14. #14
    Boolit Grand Master uscra112's Avatar
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    Red Dot will do if you don't over do it. Fast powders have to produce much higher peak pressures to get the same MV as slower ones.

    A trial Quickload model using a 350 grain bullet says 12 grains of Red Dot will generate 1200 fps at 16000 psi, while 30 grains of 4198 will get the same result at only 8500 psi. Use Red Dot sparingly if you need to preserve your supply of 4198, which may be no small thing in these days of dearth. It might well be possible to get a decent fireform using Red Dot with a caseful of Cream of Wheat - no bullet at all. I've never done it, but others have.
    Cognitive Dissident

  15. #15
    Boolit Buddy mkj4him's Avatar
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    My broken extractor replacement arrived just in time to install and use for fire forming my new BB cases. I used a 405 grain 457 bullet sized to 448 over 11, 12 and 13 grains Unique. 12 grains have 974 fps. The last didn’t register for some reason. Cases formed nicely.
    Here are my 348 Win cases to left with 380 grain 43 Mauser bullet (old west Moulds) and the BB cases and 405 bullet to right. Second case from right is unfireformed BB case. Notice how far back shoulder is.
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  16. #16
    Boolit Buddy mkj4him's Avatar
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    I also discovered that I will probably be able to size my bullets to correctly fit or at least come close to my throat measurement of .453”. Anything over .448 in the 348 Win cases would not chamber. Reason being the neck thickness on the 348 brass is .0125”. Doesn’t leave enough room. Inside diameter measurement of fired 348 case measures about .4475” or so. The neck thickness of the Bertram brass is .011” and I.D. Is .4525”.

  17. #17
    Boolit Buddy mkj4him's Avatar
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    Another tidbit of information. I did testing with and without Dacron filler over 30 grains IMR 4198.
    This was with the 380 grain .448” 43 Mauser bullet.
    Without Dacron:
    5 shots
    Average V - 1302 (high- 1410, low- 1245) SD- 64.8!!

    With Dacron:
    5 shots
    Average V - 1455 (high- 1475, low- 1441) SD- 13.5 MUCH BETTER!!

    Of course here in Florida that velocity would be a little slower during the cool weather of hunting season. Still shoots pretty straight though. I hope to get to the range and try on paper.
    Last edited by mkj4him; 08-12-2022 at 07:45 PM.

  18. #18
    Boolit Buddy mkj4him's Avatar
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    My 457 bullets, 405 grains, sized down to 450 worked well to fire form my Bertram brass cases using 13 grains of unique powder. I have established a decent load with the 380 grain bullets using a pinch of Dacron and 30 grains of IMR 4198 powder approximates military load velocities. Since I still have a good number of these 405 grain bullets That I can size down I wonder if anyone could give me a suggestion as to a start load with the Dacron and 4198 powder? I was thinking somewhere around 28 or 29 grades. Any suggestions would be appreciated. I definitely don’t want to over pressure this old gun. What would a reasonable velocity be with the 405 grain bullet?

  19. #19
    Boolit Buddy mkj4him's Avatar
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    I was wondering if anyone has a suggestion for a powder other than 4198 that would give similar velocities with the 380 grain bullets, around 1430 ft./s, that does not require the use of Dacron filler but burns consistently and provides low standard deviations for better accuracy?

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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