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Thread: Fun with the 8mm

  1. #41
    Boolit Master
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    I'm with Mauser 98K. The following method is what I use to prep the pockets on dimpled eastern bloc cases of both 5.5mm and 6.5mm primers, but for 6.5mm (.254) primers (7.62x54), a bushing must be swaged from something like 1/4" soft copper tubing which can be easier than might be thought. For cases with 5.5mm (.213-.215) primers (all 8/57 I've seen), the following process will work to completion: The Eastern Bloc cases all have that dimple on the inside of the case between the flash holes which marks the center of the anvil. I use a 5/64 "aircraft" length drill bit (5") to reach down inside the case, get centered on the dimple and drill until it starts to grab and spin the case in my hand. At this point, the tapered anvil is drilled nearly through and very thin and the case can be deprimed with a conventional decapping pin which breaks off the tip of the anvil and punches out the berdan cup. A carbide primer pocket uniformer (Lyman, I think) is chucked up in the hand drill and used to remove the remainder of the anvil and cut the pocket to the correct depth. By the way, the eastern dimpled cases fortunately have pocket depths of approximately .120, handily allowing depth uniforming to .125 for boxer primers. Some foreign cases have pockets considerably deeper (see below). Now we have a clean pocket that's .213-.215 dia. or so which must be reduced to properly fit a .210 primer. This can easily be done by clamping a long 5/16 punch (Harbor Freight) in the vise with the end of the handle resting on the vise screw housing for support and the punch sticking straight up out of the jaws. The case is inverted and dropped onto the punch and a fat center punch (too big to slip into the pocket and ground to a shallow 30-45 degrees) is centered on the primer pocket and struck to upset the brass around the pocket into the pocket to reduce its diameter to less than .210. It doesn't take much - a good crack with a 4 oz. ball peen hammer will do. Pockets are then swaged to uniform diameter with a primer pocket swage tool (mine is RCBS) just like swaging out primer crimps and they are now ready to be primed. I've done this conversion with both brass and steel cases, using them at full power and have gotten good service from both. Having three flash holes doesn't seem to have any noticeable affect on pressures or accuracy. Most of my shooting is done with .311-.312 cast boolits paper patched with three wraps of drafting vellum, bringing them to a .325-.326 diameter, perfect for the 8mm. A PP'd 175gr 311041 cast of WW over 48gr of Rel 15 speaks with some authority and shows promising accuracy, but could probably use some tweaking, which is yet another thing on the overloaded to-do list. Sometime before Fall, hopefully.

    Two things about Turkish, Egyptian and other cases from non-eastern-bloc sources: The Berdan priming system does not rely on uniform pocket depth for proper function, rather the relationship between the anvil height and the priming pellet-and-cup thickness, so the pocket depth can often be deeper than .125. Some I've attempted to convert (Turkish) resulted in seated primers being .020 below the case head and unreachable by the firing pin, thus needing a disk of material to be pressed in place to make the pocket workable with boxer primers. Nice cases, but another step I'm not willing to do unless the cases are something exotic. Also, these generally do not have the dimple between the flash holes, so they must be converted by another process - hydraulic or mechanical depriming, center drilling with a flash hole drill guide which fits into the pocket for centering purposes, etc. (A 1"-1.25" 1/4-20 set screw with a friction nut set .125 back from the end with the threads spin-filed to .210 diameter x .125 long and bored through for the 5/64 flash hole drill makes a dandy drill guide. Insert into primer pocket over the tip of the anvil with the nut against the headstamp and you're ready to drill the flash hole.) British Radway Green 7.62x51 cases are high quality and have good pocket depth, so they can be converted by this method, but boxer 7.62x51 is ubiquitous and too easy to get. I haven't gone there beyond proof of concept experimentation.
    Last edited by yeahbub; 06-11-2018 at 12:56 PM.

  2. #42
    Boolit Master Texas by God's Avatar
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    That is very interesting information but it certainly makes me glad Boxer 8x57 brass is readily gotten at present and readily obtained by reforming .270,.280, or 30-06 when it's out of stock!

    Sent from my SAMSUNG-SM-G930A using Tapatalk

  3. #43
    Boolit Master
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    DOH!! I'm mortified to realize I posted the conversion info in the WRONG THREAD! Okay, anyone know how to move it to the "Converting Berdan brass to Boxer" thread? . . . . Yeeesh, what in the world was going on there I wonder, what th'. . . dang computers mrrmnnr, harrumph, grumble snort. . . . I need a computer that does what I want it to, not what I tell it to do. . . .

  4. #44
    Boolit Master Texas by God's Avatar
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    That's hilarious! I feel your pain....

    Sent from my SAMSUNG-SM-G930A using Tapatalk

  5. #45
    Boolit Master





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    Think Past Recoil Shield!!!

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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