That said, living where i do the Chassepot´s are popular at they´re one of the few rifles permit exempt.

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This particular one has had a tool room steel insert installed to take 45-120 cartridges approx. Steel involved is as weldable as they come, so no worries there.

What we´ve done that apart is figure out a "system" to keep exempt but still realize performance.
The main culprit of the Chassepot, from an accuracy POW, being that insane forcing cone of them.

So.
We just jump that by using true bore riders. Most of them measure a minimum diameter of 11.00-11.05mm. Thus the bullets used are exactly that and in turn sport 458"-460" drivebands out back.
This brings that the cartridge used become longer, and at that rate we´re at like around the 85mm mark COAL.
But.

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We proceeded by using the utmost "culot" of (now) regular 308Win brass and a shell holder for the same. Rest i guess you can figure out.

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Using a jumbo sized straw we put cartridges together like sorts of Lego. No adhesives involved. 
One MAJOR issue with these rifles is their inherent will to soot. Like crazy.
What adds insult to injury is that in stock form the cartridges needs to be super stiff packed to be of any use, to go off.
We´ve played around with ALL other options as far as getting the blackpowder to react with grease to no avail.
But with this cartridge we´re free to just use an over powder card and then grease, before any wads and finally the bullet.
..and it works.

Now. Seeing this issue we´ve played around with duplex loads as well and in our case 70 grains of black and 7 grains of Norma 200 does it. Issue is most sanctioning bodies around here won´t allow it for comps.

Thus the rather evolved journey arriving on them cartridges and the beaut is that you can do this to an otherwise completely stock Chassepot.
All you do is replace the "umbrella" with that modified shell holder, shorten the needle and round it off.. and your´re good to go.

Does it work?

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Well, that´s 4 shots and then the flyer was certainly on me. Distance 100 meters.

Back in the old days, my gunsmith did that to get the barrel off a Luger.