8x58RD (Danish Krag) cartridge conversion

[LUTNIT]

I picked up a Swedish rolling block in 8x58RD (Danish Krag) and embarked on trying to load some ammo for it. There were several threads online I found describing it but I found almost no pictures. I figured since a bunch of these got sold in Canada I'd post up about my experience in case it can help someone else out.

The Bertram brass is $103/20pcs last I checked which is a little much if I have alternatives and I've done some cartridge conversions before so figured I'd give it a go. I ordered a set of RCBS dies from a local dealer. They're your regular reloading dies, not the special cartridge conversion dies. I'd read that you can get donor brass from 7.62x54R, .45-70, .348 Win, and .45-90. I had easy access to the first two so decided to try those two. They worked but were very short; so short they had a really hard time holding onto a bullet. I fired maybe 50-shots with these short cases but was having issues with bullets falling out of the cases so wanted something better. I wasn't able to crimp the bullets in as I had no die capable of crimping the cases with exceptionally short necks.

The .45-70 cases were just sized in the die as normal but the 7.62x54R cases had the shoulder too far down so I fire-formed them. I used 10gr of Reddot topped off with cream-of-wheat and capped with a plug of white glue. I had to fire them twice like this to get them to form well enough to where I could size and seat bullets with the dies. I did expand the necks to 8mm so they would centre in the chamber while sizing; I didn't want them to fire-form crooked.

I decided to order 50pcs of Starline .45-90 brass from Rusty Wood and it came to $85/50pcs. I tried one case without annealing and it split open right away. I annealed the rest of my test samples but went a tad too far with it. The annealing didn't go to the case heads, it's only a ~24k psi cartridge, and the forming process would have hardened them a bit so I'm not too worried. I initially overlubed my cases and got some bad denting in them. Once I cut back on the lube (I'm using Imperial/Redding sizing wax) they turned out very well.

Left - 7.62x54R (you can see the lines from the original shoulder; this case has been fired 2-3 times)
Middle - .45-70
Right - .45-90 (with denting from over lubing)

Left - .45-90 case as it came out of the bag
Second from left - (over) annealed case
Second from right - not-over-lubed case before trimming
Right - overlubed (dented) case after trimming

Left - Unannealed case split and crushed
Right - Annealed (but overlubed) case before trimming (they only grow about .050" from the conversion)

I found it worked best with turning the die in 1/2-turn per stroke to form the case. I got some wrinkles even when not over-lubed in some cases when turning the die in a full rotation per stroke.
The .45-90 rim is a touch oversized in diameter compared to 8x58RD so I just lightly pass a fine bastard file over them while rotating in my hand; nothing you need a lathe for.
The cases fit the chamber so I hammered the primer indent out of a used primer so it looked new, seated it, and when the hammer is dropped it leaves a good dent so I have confidence they'll go off just fine.

I loaded up two sets of 5rnds; one set with Trail Boss and one with 2400, both with 175gr .324" GC'ed cast bullets (the bore on my rifle slugs .3230") and I'll have to get it out to the range sometime soon. The rifle was accurate if not problematic with the 7.62x54R converted cases so hopefully it'll improve a touch.

 

[Eaglelord17]

Very nice, I love seeing the effort people go through to get some older guns up and running again.

 

[smoothbore75]

I lucked out and bought the RCBS forming die set long ago when HDS had them on sale for about 1/2 price, and like you I soon found I didn't like the short results when using .45-70 brass. I planned to experiment with
45-90 some time, so it's good to hear others' experiences going that route.
I may be on the verge of a trade with a buddy of an old Swede Mauser of mine for an old but working bench-top lathe of his, so I may be able to set up to make the rim diameters and thicknesses a bit more consistant that my last batch which I spun in a drill and touched up with a hand-file.

 

[Andy]

I did a thread on this subject nine years ago on Cast Boolits: http://castboolits.gunloads.com/showthread.php?22807-Fun-with-the-8x58R-in-a-Swedish-RB/page2.

Essentially I found that using 8X56R Hungarian brass made the most sense, but 338 Win Mag with the belt turned off was a great second choice - there just wasn't quite enough rim for reliable extractions.


Here's an extract from that thread Posted by Andy_P

After some playing, I have determined that there's another option for making 8X58RD, even though 8X56 Hungarian remains a fine solution (albeit it's difficult to find) - 338 Win Mag.

Remove the belt and a few thou from the base as required (to 0.500" - a "no-bulge" diameter), but don't touch the rim. Anneal, F/L size and trim to length and anneal again - done. The rim diameter is small, but the extractor usually catches it. The rim is also thinner than spec as is 8X56R Hungarian, but there are commonly-used techniques to compensate for that - the rim can be shimmed from behind with an o-ring, or the cast bullet can be engaged with the rifling, either of which pushes the base against the breech. After fireforming, most of us neck-size so the shoulder will maintain headspace, or the o-ring or loading method (bullet against rifling) can be maintained.

338 is my first choice among belted magnums, but so would any belted magnum, but 338 Win Mag is close to correct final length, as are 7mm Rem Mag and 264 Rem Mag - the others are all longer. The neck of the 8X58RD is below the neck of any belted magnums, so final neck thickness is the same for all (on the thick side), except that 338 gives the best start to the sizing process.
Some pics:

338 Win Mag, sized in 8X58RD die, final length (made from 45-90 is shown)



8X58RD from: 45-90; 338 Win Mag; and 8X56R



If you must have an exact replica, then use 45-90, but it's a lot of work.

If you want it easy and fast, then 8X56R is the way to go (but brass is scarce).

If neither of the above are feasible for you, then use a belted magnum.

If all else fails, then you're stuck with Bertram.

 

[vagrantviking]

I tried the 45-70 brass as I had lots. Loading with FFg. Wasn't really encouraged by the results and have meant to give it another go for the past few years but there's always something more pressing.

If all else fails it will go to Ron Smith for a 38-55 barrel or similar.

 

[Andy]

Some Loads. I consider these Max Loads for a M1889 Rolling Block. You can use 8X57 Load Data and be safe as well, since the 8X58RD has much higher case capacity than the 8X57.