This may be the bore drawing you referred to:

http://www.autochart.com/12.7x44R/12.7mm%20Rifling%20Drawing.jpg

There is some more info on the 12.7mm cartridge here:

http://autochart.com/12_7x44r.htm

Regards,
Orin

I have an Original configuration M1867 Centre-fire Carbine, in original chambering. I made cases using 8mm Lebel Military brass (Berdan primer and all) after annealing the cases, expanding out to “.50 Cal” and resizing in RCBS Dies (12.17×44), with a Trim to 44mm (Lathe).
I had earlier tried using .348 Win Brass, but found them unsatisfactory, because often the LR (.210″) primer would sit sufficiently “off centre” for the Firing Pin to NOT strike correctly (ie, into the edge of the primer) and not ignite, even after several tries.

Now you may ask about the French Berdan Primer…it is large (.250″ about) DOUBLE Cupped ( the actual Priming compound is in a .175″ cup, inside the .250″ Outer cup)
and as a result, the Anvil is shorter than for a “Normal” Berdan Primer. So just using a Normal .250 or .254″ Berdan primer will result in “misfires”(there is too much space between compound and anvil…I resolved this Problem by increasing Anvil Height with a LR/LP Anvil, converting the Primer into a “Double Flash-hole Boxer”

This gave sufficient extra Anvil height to ignite the primer EVERY time, even with an “Off centre” case…Berdan primers, especially the Large ones, Ignite best by a slightly “Off centre” FP strike…Look at fired .303 British cases using the Large Berdan primer…all the FP strikes are “off to one side”, ensuring the Priming compound is crushed between cup and anvil Top and Side.

I found this problem initially making Blanks for many older BL BP rifles (for Movies) and found that the 8mm lebel Military cases (I have a lot of “Pull-down” 1940s Hotchkiss MG ammo (dead Primers) and having access to excellent RWS #6000 (.303 bgr) and #6504 (7,62x54Russian) Primers here Down Under, I could experiment with a case form which closely replicates the original 12,17 case.

Of course, with PRVI new 8mm Lebel cases (Boxer) the case problem is kinda resolved, but the “off-centre Primer” (LR size) can still be a Problem.

BTW,. “why 12.17″ and “12,7”…the Bore of the Rifle Barrel…some time ago GB /IAA (??) showed a Design of the original Barrel cross section, with the Measurements of the Segmental Rifling of the Norwegian Remingtons…, The Bore is “12,17mm”, the Grooves are “13,25mm” and the Common name for the Cartridge is also “12,7×44″ ( ie .50 cal)

To note that “12,7” is the average (Median) diameter of the Barrel. ( actually shown on the (Norwegian) designs).

Anyway, with .525″ cast bullets, it makes an excellent close range “Pig Gun” ( for feral Grunters very common in Queensland, especially in the Northern Cane Fields)

Just that it is relatively slow, being single shot…Grunters are usually in mobs of five to 10, and all sizes.( I actually prefer a Bolt gun, Mauser; or a Pump 12ga. with OO or Slug)

Doc AV
Down Under.