I have become intrigued by the 6x70R calibre from Norma and others . It's a very low pressure round and seems to be very suitable for a lightweight combination gun . I would like to hear opinions from others about a suitable action . As low weight is a priority could I build a combination gun on a 410 action ? The back thrust of this pencil shaped round is about that of a hornet if I understand correctly .
Would a sleeved 6mmm barrel on a 410 action be safe ?
I rather like the old back action hammer guns as they are pretty strong .
What do you think , guys ?

Considered to be an excellent caliber for roe deer and fox...shoots 90 gr at 2450/ft sec. In real world terms about as useful as the 5.6x52R (70gr at 2800) or step up a bit to the 25-35. I should think a Martini action would be just the ticket for a single shot. An insert would do the trick for a SxS in 410. Might be cheaper to buy an Einstecklauf in Germany in which case you might need to start with a 20 gauge shotgun. Still with the right SxS you could still be in the low 6LB range. These inserts are being sold at bargain prices in Germany right now. They typically weigh about 600gm and would be lighter than a sleeve, IMO.

Its a long cartridge and I doubt it would make the curve on a Martini.
I would build on on a 20 gauge frame, mono blocked in; I prefer to thread them but others just solder them and that works. A sleeved 410 would leave you with very thin chamber walls.....You do not want to rely on the parent barrel wall for radial strength.

A 6x70R Einstecklauf is selling in Germany right now for about 5/600 Eu. K & S would be my pick. Have a smith fit it to a 20 ga and you can take it in and out when you want...and still have a 20 ga shotgun when needed.

Sounds like a lot for a barrel insert......

Normal sleeving for a shotgun barrel probably costs $4-500. Throw in chambering and rifling for the cartridge don't think it would be that much less if at all. You also wouldn't have the versatility of having the 20 gauge as a shotgun. Sleeving is also going to be heavier I would imagine. Could be import to Auz could be too expensive.

Thanks for your replies. I'm grateful for them .
I'm still rather fond of the monoblock on a 410 action / frame .
Why ? The backthrust on this round is very low .The 2007/2008 edition of the waffen Frankonia has Norma pressures for their rounds . The 6x70R is shown as 2600 bar . The 5.6x52r (22 Savage ) is shown as 3300 bar .That's quite a difference . As well the 6x70R has a narrower base : .351 for 6x70R and '410 for the 22 savage ( my measurement ). So the backthrust from the Savage is greater over a larger area .
The hornet has higher pressure as well. RWS in the same catalogue shows the hornet as 3200 bar . My measurement of the hornet base is '292 , a smaller are of backthrust but significantly higher pressure .
It does seem that the 6x70R is lightly loaded by Norma. One figure I read ( lost source now ) showed 39 grains of water(?) while the 22 Savage has 33 grains of water as does the 25/35 winchester .
I can understand the design by Norma is well thought out : low backthrust but higher velocity from the elongated cartridge but underloaded .
My concern is that pointed out by dpcd of thin chamber walls .
I also note that Lothar Walther sell a chambered barrel for the 6x70R which weighs 1.3 lbs at 334 US dollars .
As you can see ( chuckle ) I'm trying to justify a project .
Thanks Again